Science scheme of work for the State of Qatar · scheme of work reflects Qatari values and culture...

Science scheme of work

for the State of Qatar

Grades 7 to 9

Developed for the Education Institute by CfBT

2 | Qatar science scheme of work | Grades 7 to 9 © Education Institute 2005


Contents

1 Introduction 5

2 Outline of the units for each grade 7

3 Units of work: Grades 7 to 9 35

Grade 7 41

Grade 8 157

Grade 9 267

Background to this document The new Curriculum Standards for Arabic, English, mathematics and science lie at the heart of Qatar’s education reforms. The standards draw on international expectations for what students should know, understand and be able to do at each stage of their schooling.

The new standards were introduced into Qatar’s Independent Schools in September 2004.

This optional scheme of work for science is a long-term teaching plan. It consists of units of work for each grade showing how the standards can be taught. It has been developed by the Centre for British Teachers (CfBT), who also developed the standards, guided by the staff of the Education Institute.

Local curriculum specialists and teachers have helped to ensure that the scheme of work reflects Qatari values and culture and is relevant to the needs and interests of Qatari students.

The complete scheme of work covers Grades 1 to 12. This document contains the materials for Grades 7 to 9. Similar documents contain the science scheme of work for other grades.


Acknowledgements The questions on the assessment pages include some that are based on or are adapted from the National Curriculum tests for England or released items used in the international tests TIMSS (1993) or TIMSS-R (1998), or example items for TIMSS 2003, all published by the International Association for the Evaluation of Educational Achievement, The Hague, Belgium. The activities in the science scheme of work for Grades 7 to 9 include some drawn from materials published by the Department for Education and Skills, England. We are grateful to the Qualifications and Curriculum Authority for England and the Department for Education and Skills for agreeing that these examples may be used. Some of the activities include diagrams based on diagrams from other sources. The sources of such diagrams are acknowledged on the pages where they appear. We are grateful to those individuals, companies and institutions who have agreed that their diagrams may be used in this publication.

Disclaimer

We are not responsible for the actual content of any materials suggested as information sources in this document, whether they be printed publications or on a website. We have checked all the website references at the time of writing but the constantly changing nature of the Internet means that some sites may alter at a later date. We have made every effort to trace all copyright holders. We apologise for any acknowledgement omissions and welcome any additions or amendments for inclusion in any reprint.

Conventions used The spelling conventions used in the scheme of work are based on standard British English.

The units of measurement and abbreviations used in the scheme of work are the Système Internationale (SI) units. They are written in their internationally recognised form: for example, the word centimetre and its abbreviation cm are used. Thin spaces, not commas, are used to separate groups of three digits in numbers with more than four digits: for example, 48 746, not 48,746.

Numbers and symbols are written using Roman or Greek script. Equations and formulae are presented from left to right.

Schools will need to make their own decisions about spelling conventions and how numbers, symbols, equations and formulae are presented to students in lessons and learning resources, taking account of the language of instruction and the age of the students.


1

Introduction

This introductory section is intended to give some guidance about how schools might use the scheme of work.

Decisions about how best to teach the curriculum standards are left to schools. Each school can develop its own policies for lesson planning, teaching and learning, and assessment, so that as many students as possible achieve the standards expected for their grade.

There is no requirement for Independent Schools to use the scheme of work. Schools may use as little or as much of it as they find helpful, supplementing the materials or adapting them where appropriate to meet their students’ needs and the teaching time that they have available.

A scheme of work The cycle of planning, teaching and assessment is a continuous one. Good teaching is based on good planning, and good planning is informed by effective assessment.

Assessment

Planning

Teaching

The Qatar scheme of work for Grades 1 to 12 is a long-term plan to help schools to achieve the aims for science, stated in the Introduction to the

standards. It interprets the new Curriculum Standards and translates them into coherent, manageable teaching units, typically 6 to 12 hours of work.

The scheme shows how the units can be distributed within each grade and across grades in a sequence that promotes continuity and progression in students’ learning. The units then act as a guide to teachers when they create their lesson plans.

Modifying the scheme of work

Adding further material

There is no right or wrong way to present a scheme of work: it can be set out in any way that is useful to teachers.

Schools that choose to use the scheme of work may decide to add further details to it, such as:

• extra notes to help teachers to interpret the scheme of work: for example, teaching points, references to ICT, common misunderstandings, suggestions for extension activities and for homework;

• more ideas for differentiated activities to cater for students who are very able or who need extra support;

• further assessment activities to help teachers to judge students’ progress;

• suggestions for links that can be made across subjects such as Arabic and English, or science and mathematics;

• out-of-school activities that can enhance learning in school.

Changing parts of the scheme of work

Some schools may decide to modify the whole scheme of work, the units for one or more grades, or particular units. Some possible modifications are to:

• emphasise or expand particular parts of the scheme;

• vary contexts, resources or activities to take account of the different interests of boys and girls;


• add to one or more units some objectives based on standards for a higher grade in order to give students opportunities to progress more rapidly;

• identify the essential supporting standards that need to be taught before the grade-specific standards;

• give students more time for particular aspects of the scheme, or opportunities to revisit knowledge and skills in different contexts;

• adapt activities to provide greater support for students with difficulties in language or literacy, or for students who are being taught in English.

The support provided for students with difficulties in language and literacy or who are being taught in English could include:

• reducing the amount of written work and reading;

• giving students the opportunity to clarify their ideas through discussion, the use of diagrams and other visual aids, and the use of scientific apparatus, rather than relying on written materials.

There is more advice on teaching science in the medium of English later in this document (see page 40).

Reviewing an existing scheme of work Some schools may already have a scheme of work that they have developed. These schools may want to review their scheme of work and supplement it with parts of the scheme of work in this document.

Some questions to ask when reviewing an existing scheme of work are as follows.

• How firmly is the scheme linked to the standards?

• Does it build up concepts in an organised, systematic and rigorous way?

• Does it identify what students are expected to learn, and how students’ learning may be assessed?

• Does it describe appropriate teaching and learning activities? Are the activities linked to the learning that they are intended to promote?

• Does the scheme provide opportunities to develop ICT skills and, where appropriate, links with other subjects, such as mathematics?

• Are the resources needed to teach the scheme identified? Are these resources appropriate to the age and ability of the students?

• Does the scheme indicate the time needed to teach each unit, consistent with your school’s timetable for science?

• Is there enough detail in the scheme to help teachers when they plan lessons?

• Does the scheme allow for some flexibility when it is used?


2

Outline of the units for each grade

Content of the scheme of work The Qatar scheme of work for science:

• draws the standards together into coherent, manageable teaching units;

• indicates the approximate number of teaching hours for each unit;

• orders the units across two semesters of the school year so that they build on preceding work, link with other units and prepare students for the next grade;

• develops sufficient detail in each unit about what to teach and how to teach it for teachers to be able to create a series of lesson plans from it.

The flow of the units reflects continuity and progression in students’ learning throughout the school year. The sequence provides one or more opportunities to revisit particular standards or groups of standards throughout the course of the year. This gives students the chance to consolidate their learning in a range of contexts and to make connections between different aspects of the subject.

The example diagram on the right shows how units of work are organised and sequenced in the scheme of work for Grade 7

The diagrams sequence units within content strands of the science standards (life science, materials, Earth and space and physical processes). It is left to schools to determine the first unit to be undertaken in a grade and whether or not to do to more then one unit in a content strand before teaching a unit from another strand.

The diagrams summarising the units also indicate the break between the first and second semesters. This is a rough guide only. Schools should carry on teaching the units regardless of when the break occurs.

Science scheme of work: Grade 7 units 136 hours1st semester68 teaching hours

Unit 7LS.0: Preliminary unitIntroduction to grade and revision ofkey ideas from previous grades.1 hour

Life science: 23 hours Materials: 21 hours Physical processes: 24 hours

Unit 7L.1: Specialised cellsFunctions of parts of a cell. Specialisedcells.7 hours

Unit 7L.2: Human reproductionMale and female reproductive systems.Pregnancy. Development and birth of ababy. Care of a newborn baby.8 hours

Earth and space: 0 hours

Unit 7M.0: Preliminary unitIntroduction to grade and revision ofkey ideas from previous grades.1 hour

Unit 7M.1: Particulate nature ofmatterEvidence for particles. Explanation ofcommon phenomena in terms ofparticles.10 hours

Unit 7P.0: Preliminary unitIntroduction to grade and revision ofkey ideas from previous grades.1 hour

Unit 7P.1: Measurement and densityMeasurement of mass and length.Floating and sinking. Calculatingdensity.8 hours

Unit 7L.3: VariationInherited and environmental variation.Selective breeding.7 hours

Unit 7M.2: Mixtures, compounds andelementsSeparation of mixtures. Characteristicsof pure materials. Elements and theformation of compounds.10 hours

Unit 7P.2: ElectrostaticsPositive and negative charge. Pointdischarge and lightning.7 hours

Unit 7P.3: MagnetismMagnetic materials. Earth's magneticfield. Magnetic poles and lines of force.8 hours

2nd semester68 teaching hours

Unit 7L.R: Review unitRevision of key ideas from firstsemester.1 hour


Unit 7L.4: Growing plantsWater and nutrient uptake in plants.Nutrients required for plant growth.7 hours

Unit 7L.5: SoilRole of micro-organisms in nitrogenfixation, soil decomposition andrecycling nutrients.6 hours


Unit 7M.R: Review unitRevision of key ideas from firstsemester.1 hour

Unit 7M.3: CombustionBurning. Composition of air. Propertiesof nitrogen and oxygen.7 hours

Unit 7P.R: Review unitRevision of key ideas from firstsemester.1 hour

Unit 7P.4: The effects of forcesEffects of forces. Gravitationalattraction. Balanced forces. Centre ofgravity and stability.9 hours

Unit 7M.4: AcidityAcids and alkalis. Neutralisation. pHscale and indicators. Action of acids oncarbonates.8 hours

Unit 7P.5: Electrical circuitsSeries and parallel circuits. Hazards ofmains electricity.9 hours

Unit 7L.6: Food websFood webs and food chains in differentecosystems. Impact of humans andenvironmental change on food webs.8 hours

Unit 7E.0: Preliminary unitIntroduction to grade and revision ofkey ideas from previous grades.1 hour

Unit 7E.1: Origins and properties ofrocksStructure of the Earth. Formation andproperties of igneous, sedimentary andmetamorphic rocks. Minerals.Geological timescale.10 hours

The diagrams illustrate only one way of grouping the standards and ordering the teaching units for the grades. Schools can decide:

• to use this model in full;

• not to use the model; or

• to customise individual units or vary the order to suit their own circumstances.

9 | Qatar science scheme of work | Outline of units © Education Institute 2005


2nd semester44 hours

Unit 1L.1: Characteristics of living thingsCommon features of living things.10 hours

Unit 1.0: Introductory unit

8 hours

Unit 1 M.1: Identifying materials and their usesIdentification, physical properties and uses ofcommon materials.12 hours


UNIT 1 P.1: Sensing heat and lightUse of senses, sources of heat and light, andorgans used for detection.8 hours

Unit 1P.2: Sensing soundUse of senses, sources of sound, and organsused for detection.7 hours

Unit 1L.R: Review unitRevision of key ideas from first semester.1 hour

Unit 1M.R: Review unitRevision of key ideas from first semester.1 hour

Unit 1M.2: Classifying materialsClassifying objects according to the material fromwhich they are made. Multiple uses of a material.12 hours

Unit 1P.R: Review unitRevision of key ideas from first semester.1 hour

Unit 1P.3: Moving thingsMovement of objects, including pushes and pulls.11 hours


Unit 1L.3: HabitatsVariety and vulnerability of habitats.10 hours

Unit 1L.2: Changes to organisms over timeHow organisms change with seasons and age.8 hours




Unit 2L.0: Preliminary unitIntroduction to grade and revision of key ideasfrom previous grade.2 hours

Unit 2M.0: Preliminary unitIntroduction to grade and revision of key ideasfrom previous grade.2 hours

Unit 2M.1: Properties of materialsDescription, classification and uses of materials.8 hours


Unit 2P.0: Preliminary unitIntroduction to grade and revision of key ideasfrom previous grade.2 hours

Unit 2P.1: ForcesIdentification and exploration of forces. Effect offorce on speed.12 hours

Unit 2L.R: Review unitRevision of key ideas from first semester.2 hour

Unit 2M.R: Review unitRevision of key ideas from first semester.2 hour

Unit 2M.3: Changing materialsProperties of common materials. Permanent andtemporary changes to materials.6 hours

Unit 2P.R: Review unitRevision of key ideas from first semester.1 hour

Unit 2P.2: ElectricityIdentification and use of common electricaldevices. Simple circuits and batteries.12 hours


Unit 2L.4: Care of the environmentCare of the environment, including the efforts oflocal industry.7 hours

Unit 2L.3: HabitatsRelationship between organisms' characteristicsand their environment.9 hours

Unit 2L.1: Animal body partsIdentification and purpose of visible body parts.8 hours

Unit 2L.2: PlantsCycle of seed to flowering plant. Water and plants.6 hours

Unit 2M.2: Investigating materialsInvestigation of materials.7 hours

Unit 2M.4: Natural and synthetic materialsPermanent and temporary changes to natural andsynthetic materials.4 hours




Unit 3L.0: Preliminary unitIntroduction to grade and revision of key ideasfrom previous grades.2 hours

Unit 3M.0: Preliminary unitIntroduction to grade and revision of key ideasfrom previous grades.2 hours

Unit 3M.1: Comparing materialsComparison, identification and classification ofmaterials by physical properties. Variety of uses ofsome materials.10 hours


Unit 3P.0v: Preliminary unitIntroduction to grade and revision of key ideasfrom previous grades.2 hours

Unit 3P.1: Forces, magnets and springsSize and direction of forces. Magnets and springs.11 hours

Unit 3L.R: Review unitRevision of key ideas from first semester.2 hours

Unit 3M.R: Review unitRevision of key ideas from first semester.2 hours

Unit 3M.2: Investigating materialsRelationship between materials' properties andtheir uses. Testing materials.10 hours

Unit 3P.R: Review unitRevision of key ideas from first semester.2 hours

Unit 3P.2: Shadows, mirrors and magnifiersRelationship between light and transparent/opaque materials. Shapes of shadows. Magnifiers.14 hours


Unit 3L.4: Body parts and functionsFunctions of internal body parts of humans andother animals. Heart rate and exercise.12 hours

Unit 3L.1: Classification of plants and animalsRecognising and grouping plants and animals.7 hours

Unit 3L.2: Growing living thingsFactors affecting growth of green plants.7 hours

Unit 3L.3: Micro-organismsClassification of micro-organisms.4 hours



Unit 4L.0: Preliminary unitIntroduction to grade and revision ofkey ideas from previous grades.2 hours


Unit 4L.1: Diversity of habitats andliving thingsUse of branching keys to identifyorganisms. Habitats and theirinhabitants.10 hours

Unit 4L.2: Protection of habitatsProtection of habitats.8 hours


Unit 4P.0: Preliminary unitIntroduction to grade and revision ofkey ideas from previous grades.2 hours

Unit 4P.1: SoundSounds and how we hear them.11 hours

Unit 4M.0: Preliminary unitIntroduction to grade and revision ofkey ideas from previous grades.2 hours

Unit 4M.1: Solids, liquids and gasesStates of matter. Changes of state.Common gases.10 hours

Unit 4M.2: MetalsUseful properties of metals.4 hours


Unit 4L.R: Review unitRevision of key ideas from firstsemester.2 hours


Unit 4L.3: Life cycles of animals andplantsLife cycles of animals and reproductivecycle of flowering plants.12 hours

Unit 4L.4: Healthy livingInternal regulation of life processes.Impact of illness, injury and behaviouron life processes.7 hours


Unit 4E.1: Earth and spaceThe Sun. The Earth's movement on itsaxis. Shadows. Day and night.11 hours

Unit 4P.R: Review unitRevision of key ideas from firstsemester.2 hours

Unit 4P.2: Heat and temperatureMeasuring temperature. Conductionand insulation.12 hours



Unit 5L.0: Preliminary unitIntroduction to grade and revision ofkey ideas from previous grades.1 hour


Unit 5L.1: Staying aliveBasic needs of living things. Growthand reproduction.6 hours

Unit 5L.2: Life cyclesComparison of life cycles of humansand other mammals.6 hours


Unit 5L.3: Food chainsHerbivores, carnivores and omnivores.Food chains in different ecosystems.6 hours


Unit 5M.1: WaterThe water cycle. Water as a solvent.Drinking water and waste water.10 hours


Unit 5P.1: Static electricityElectrostatic charge. Repulsion andattraction.6 hours

Unit 5P.2: MovementMeasuring speed. Changing speed.6 hours

Unit 5P.3: FrictionMeasuring forces. Friction betweensurfaces. Water and air resistance.11 hours


Science scheme of work: Grade 5 units 107 hours2nd semester53 teaching hours



Unit 5L.4: FoodFood as an energy source. Balanceddiet. Food requirements for differentlifestyles.8 hours

Unit 5L.5: VertebratesFeatures of different vertebrate groups.Variation.8 hours


Unit 5.R: Review unitRevision of key ideas from firstsemester.1 hour

Unit 5M.2: Making things bychanging materialsMaking and testing useful materials.Mixing and cooking materials in thekitchen. Classifying changes.10 hours


Unit 5P.4: Magnetic forcesMagnetic attraction and repulsion.5 hours

Unit 5P.5: Making electrical circuitsSimple circuits. Effect of cells in series.8 hours

Unit 5E.0: Preliminary unitIntroduction to grade and revision ofkey ideas from previous grade.1 hour

Unit 5E.1: Rocks and how we usethemComparing different kinds of rocks.Using rocks. Soil formation. Differentkinds of soil.10 hours





Unit 6L.1: CellsPlant and animal cell structure. Tissuesand organs.6 hours

Unit 6L.2: Harmful micro-organismsCommon illnesses caused by micro-organisms. Spoiling of food.6 hours



Unit 6M.1: SolubilityDifferences in solubility. Uses ofdifferent solvents.7 hours

Unit 6P.0: Review unitIntroduction to grade and revision ofkey ideas from previous grades.1 hour

Unit 6P.1: Different kinds of forcesContact forces and forces that act at adistance. Gravity. Mass and weight.8 hours


Unit 6E.1: Movement of the Earth andthe MoonPhases of the Moon. Day and night.Seasons. Tides. Eclipses.12 hours

Unit 6L.3: ClassificationMajor groups of animals and plants.Using branching keys.6 hours

Unit 6M.2: Making pure substancesfrom mixturesRecovery of the solute and solvent.Everyday examples of filtration.6 hours



Unit 6.R: Review unitRevision of key ideas from firstsemester.1 hour


Unit 6L.4: Teeth and eatingDigestive system. Teeth and toothdecay.8 hours

Unit 6L.5: Organs and systemsFunction of human organs. Puberty andreproductive organs. Organs of plants.Structure of a flower.8 hours


Unit 6M.R: Revision unitRevision of key ideas from firstsemester.1 hour

Unit 6M.3: Changing materialsChemical change. Reversible andirreversible changes.9 hours


Unit 6P.2: LightPropagation, absorption and reflectionof light.11 hours

Unit 6M.4: Heating and burningBurning and action of heat onsubstances. Temporary and permanentchanges.7 hours

Unit 6P.3: The effects of forcesForces and changes of shape andmovement. Terminal velocity.6 hours





Unit 8L.1: Gas exchangeStructure and function of lungs. Effectof smoking. Red and white blood cells.8 hours

Unit 8L.2: CirculationStructure and function of heart.Circulation and blood vessels.8 hours



Unit 8M.1: Atoms and moleculesAtoms and molecules. Elements andcompounds. Chemical symbols andequations.7 hours


Unit 8P.1: EnergyForms of energy. Energytransformation. Measuring energy.10 hours

Unit 8M.2: MetalsReactivity series. Corrosion. Action ofacids and the properties of hydrogen.9 hours

Unit 8P.2: ElectromagnetismElectromagnets and motors.8 hours

Unit 8L.3: Micro-organisms and foodMicro-organisms in food, wine and beerproduction.5 hours


Unit 8E.1: The Solar SystemThe Sun, stars and planets.8 hours





Unit 8L.4: PhotosynthesisChlorophyll and chloroplasts. Processof photosynthesis.7 hours

Unit 8L.5: Feeding relationshipsPyramids of number and biomass.Accumulation of toxins in a food chain.7 hours



Unit 8M.3: Uses of metalsMetals and non-metals. Properties anduses of metals. Occurrence andextraction of metals.10 hours


Unit 8P.3: Heat and temperatureTemperature scales. Heat capacity.Conduction, convection and radiation.12 hours

Unit 8M.4: SaltsPreparation and uses of common salts.9 hours

Unit 8P.4: LightLight intensity. Reflection, refractionand dispersion. Colour.12 hours

Unit 8L.6: DigestionStructure and function of digestivesystem. Process of digestion. Role ofenzymes in digestion.8 hours





Unit 9L.1: Cell activityCell division. Movement of substancesin and out of cells by diffusion andosmosis.8 hours

Unit 9L.2: Respiration andphotosynthesisAerobic respiration in plants andanimals. Comparison of respiration andphotosynthesis.11 hours



Unit 9M.1: Atomic and molecularstructureStructure of the atom. Covalent andionic bond formation. Metallic bonding.Valency. Structure and properties ofcompounds.12 hours


Unit 9P.1: PressurePressure in solids, liquids and gases.Pneumatics and hydraulics.6 hours

Unit 9M.2: PollutionCauses and effects of air and waterpollution. Local and global pollutionissues.12 hours

Unit 9P.2: Electricity and energyPotential difference and resistance.Ohm's law. Potential difference andenergy. Electricity generation,transmission and use. Electrical energyand power.12 hours

Unit 9L.3: Disease and micro-organismsMicro-organisms and disease. Functionof antibodies, antibiotics andvaccination.10 hours

Unit 9P.3: WavesTransmission of energy in longitudinaland transverse waves. Velocity,frequency and wavelength. Reflectionand refraction.12 hours

Unit 9P.4: The electromagneticspectrumElectromagnetic radiation and theelectromagnetic spectrum. Properties ofdifferent forms of radiation.4 hours





Unit 9L.4: MovementBones and joints of human skeleton.Antagonistic muscle action.6 hours

Unit 9L.5: InheritanceSexual and asexual reproduction.Cloning and genetic engineering.Inheritance of sex. DNA, genes andalleles. Inherited disorders. Evolution.12 hours



Unit 9M.3: Energy resourcesEndo- and exothermic changes.Reaction energy profiles. Origins anduse of fossil fuels.10 hours


Unit 9P.5: Moments and leversWork. The lever and other simplemachines. Moments.9 hours

Unit 9M.4: PolymersNatural and synthetic polymers andtheir uses. Cement and concrete. Clayand ceramics.12 hours

Unit 9P.6: StructuresCompressive and tensile strength ofmaterials. Use of materials in buildingsand bridges.7 hours

Unit 9L.6: Hormones and nervesHomeostasis and role of hormones.Nervous system and types of nerves.Structure of human eye and ear.11 hours

Unit 9E.1: The visible UniverseStars and galaxies. Creation, life anddeath of stars. Planetary formation.Evolution of the Universe.12 hours

Unit 9P.7: SoundSound transmission in air and othermedia. Functioning of the ear.8 hours


Science scheme of work: Grade 10 foundation units 178 hours1st semester83 teaching hours

Unit 10FB.0: Revision unitRevision of key ideas from Grade 9.1 hour

Biology: 28 hours Chemistry: 25 hours Physics: 30 hours

Unit 10FB.1: Biologically important moleculesStructure of some biological molecules. Chemicaltests for proteins, sugars and starch.Chromatography and electrophoresis.12 hours

Unit 10FB.2: Cell ultrastructureProkaryotic and eukaryotic cells. Cell organelles andtheir functions.9 hours

Unit 10FC.0: Revision unitRevision of key ideas from Grade 9.1 hour

Unit 10FC.1: Structure and bonding in matterStructures of atoms. Atomic and molecular masses.Chemical bonding. States of matter.11 hours

Unit 10FP.0: Revision unitRevision of key ideas from Grade 9.1 hour

Unit 10FP.1: Using physical quantitiesSI units. Precision and accuracy. Assumptions inproblem solving. Vectors and scalars.7 hours

Unit 10FC.2: Water and oilPurification techniques. Properties and fractionationof air. Fractionation of petroleum. Hardness anddistillation of water.6 hours

Unit 10FP.2: Kinematics and mechanicsDisplacement, speed, velocity and acceleration. Effectof forces on an object. Combination and resolution offorces. Frictional and viscous forces.10 hours

Unit 10FB.3: Enzyme actionMechanism of enzyme action. Competitive and non-competitive inhibition. Factors affecting enzymeaction.7 hours

Unit 10FP.3: Behaviour of matterKinetic particle model. Changes of state. Thermalexpansion. Density and pressure. Hydraulics.Flotation.12 hours

Unit 10FC.3: Obtaining chemicalsElectrolysis. Halogens. Metal extraction.Environmental issues and recycling.7 hours


Unit 10FC.7: Reaction ratesFactors affecting the rate of chemical reactions.Reaction rate and kinetic modelling. Catalysis.Equilibria and dynamic reactions.8 hours

Science scheme of work: Grade 10 foundation units 178 hours2nd semester95 teaching hours

Unit 10FB.4: DNA and protein synthesisDNA structure and replication. The genetic code.Protein synthesis, mRNA and tRNA.6 hours


Unit 10FB.5: Variation in populationsChromosomes in diploid and haploid cells. Gametesand sexual reproduction. Environmental and geneticvariation.9 hours

Unit 10FB.6: Human health and diseaseClassification of diseases and illnesses. Endemic,epidemic and pandemic diseases. Diet, lifestyle andhealth.9 hours

Unit 10FC.4: Chemical patternsPeriodicity. Trends in the periodic table (period 3,groups I, II, VII, VIII). Transition metals.8 hours

Unit 10FC.5: Acids and saltsStrong and weak acids and alkalis, pH.Neutralisation, indicators, salts, buffers.9 hours

Unit 10FP.4: Sound and wavesPulses and travelling waves. Longitudinal andtransverse waves. Production and nature of soundwaves. Standing waves and resonance. Musicalinstruments.11 hours

Unit 10FP.5: Magnetism and electrostaticsMagnetic fields of permanent magnets. Ferromagneticmaterials. Forces between electric charges. Electricfields.9 hours

Unit 10FC6: Chemistry in the environmentCarbon, nitrogen and water cycles. Atmospheric andwater pollution. Controlling and reduction ofpollutants. Global warming and climate change.10 hours

Unit 10FP.6: ElectromagnetismCurrent and charge. Conductors, semiconductors andinsulators. Electromagnetic force. DC motor. Halleffect.10 hours

Unit 10FB.7: Ecosystems: energy flow andmicro-organismsEnergy flow in food chains and food webs. Micro-organisms and recycling. Nitrogen-fixing bacteriaand mutualism.6 hours


Unit 11FC.3: Electrochemical cellsCell potentials and electrochemical cells.Environmental issues and rechargeable cells.10 hours


Unit 11FB.0: Revision unitRevision of key ideas from Grade 10.3 hours


Unit 11FB.1: Linking cell structures to functionMitochondria, ATP and biochemistry of aerobicrespiration. Cell membrane structure and transport.9 hours

Unit11FB.2: Human transport systemHuman blood system, heart structure and function.Blood vessels and red blood cells.10 hours

Unit 11FC.0: Revision unitRevision of key ideas from Grade 10.3 hours

Unit 11FC.1: Obtaining chemicals revisitedHaber process, nitric acid and fertilisers. Sulfur andthe contact process. Limestone and cement.10 hours

Unit 11FP.0: Revision unitRevision of key ideas from Grade 10.3 hours

Unit 11FP.1: Movement and forcesNewton's laws of motion. Mass and weight. Force,mass and acceleration. Inertial and gravitationalmass. Momentum conservation.15 hours

Unit 11FC.2: MetalsReactivity series of metals. Alloys. Oxidation andreduction.7 hours

Unit 11FP2: Temperature and heatThermal energy transfer and equilibrium. Conduction,convection and radiation. Convection currents andweather. Specific heat capacity and latent heat.11 hours

Unit 11FB.3: Human gas exchange system andhealthGas exchange structures and functions. Exercise,pulse rate and blood pressure. Lung diseases.Effect of smoking.9 hours

Unit 11FP.3: Optics and lightReflection and refraction. Image formation. Long andshort sight. Total internal reflection. Dispersion.11 hours



Unit 11FB.4: Biological basis of InheritanceHomologous chromosomes. Mitosis and meiosis.DNA, genes and variation. Mutations.9 hours


Unit 11FB.5: Diversity of lifeClassification of organisms. Micro-organisms. Cellculture.10 hours

Unit 11FB.6: Ecological relationships andpopulationsInteractions between organisms. Populationdynamics. Human impact on the environment.10 hours

Unit 11FC.4: Reaction rates revisitedExothermic and endothermic reactions. Activationenergy and energy profiles. Catalyst and activationenergies. Bond breaking and making.10 hours

Unit 11FC.5: An introduction to organic chemistryNomenclature, structure, bonding and shape.Alkanes and alkenes. Aliphatic electrophilic andnucleophilic addition and substitution reactions.10 hours

Unit 11FP.4: Current electricityCurrent and charge. Conductors, semiconductors andinsulators. Voltage and resistance. Electrical power.Internal resistance.10 hours

Unit 11FP.5: Electronic control circuitsCapacitors and diodes. Variable resistors and theiruse in potential divider circuits. Logic gates and truthtables. Switches and memory circuits.10 hours

Unit 11FC.6: Some functional groupsAlcohols, halogen compounds, aldehydes andketones, carboxylic acids and their derivatives.10 hours



Unit 12FB.0: Revision unitRevision of key ideas from Grade 11.3 hours


Unit 12FB.1: Introduction to photosynthesisStructure and function of leaf and chloroplasts.Biochemistry of photosynthesis. Factors limitingphotosynthesis.12 hours

Unit 12FB.2: Transport systems indicotyledonous plantsVascular systems of plants. Movement of water,transpiration and translocation.8 hours

Unit 12FC.0: Revision unitRevision of key ideas from Grade 11.2 hours

Unit 12FC.1: Chemical bondingIntermolecular forces. Dative bonding.10 hours

Unit 12FP.0: Revision unitRevision of key ideas from Grade 11.3 hours

Unit 12FP.1: Energy, work and powerWork, force and displacement. Kinetic and potentialenergy. Energy transfer and conservation. Efficiency.Power.12 hours

Unit 12FC.2: Calculating quantitiesPhysical properties related to bonding type.Quantitative treatment of moles, molarity and molarvolume. PV = nRT.13 hours

Unit 12FB.3: Physiological regulation inmammalsHomeostasis. Thermoregulation. Oestrous cycle.Nervous and hormonal control systems.12 hours

Unit 12FP.2: Wave propertiesReflection and refraction. Refractive index. Diffraction,superposition and interference. Doppler effect.Properties and nature of electromagnetic waves.Polarisation of transverse waves.15 hours



Unit 12FB.4: The HIV/AIDS pandemicCauses, transmission and control of HIV/AIDS.Action of antibodies.5 hours


Unit 12FB.5: Genetic inheritance and naturalselectionMonohybrid crosses. Genetic variation. Sex-linkedcharacteristics. Natural selection and evolution.12 hours

Unit 12FB.6: The basis of biotechnologyUses of micro-organisms. Principles of geneticengineering. Arguments for and against GMOs.8 hours

Unit 12FC.3: A closer look at some elementsChemistry of O, S, N, P, C, Si and transition metals.12 hours

Unit 12FC.4: Some arene chemistryComparison of arenes with aliphatic compounds.12 hours

Unit 12FP.3: Electricity generation andtransmissionProduction of induced e.m.f. Magnetic flux. Faraday'sand Lenz's laws. Eddy currents. AC generation. Thetransformer.15 hours

Unit 12FP.4: Nuclear and atomic physicsRutherford scattering. Nuclear model of atom. Nucleartransformations. Nuclear decay and half-life.Properties of nuclear radiations. Uses ofradioisotopes. Nuclear fission and fusion. Cathode raytubes.15 hours

Unit 12FC.5: Giant moleculesAddition and condensation polymerisation. Fats andoils. Natural polymers.11 hours


Science scheme of work: Grade 10 advanced units 179 hours1st semester95 teaching hours

Unit 10AB.0: Revision unitRevision of key ideas from Grade 9.1 hour


Unit 10AB.1: Biologically important moleculesStructure of biological molecules. Chemical tests forproteins, sugars and starch. Chromatography andelectrophoresis.9 hours

Unit 10AB.2: Cell ultrastructureProkaryotic and eukaryotic cells. Cell organelles andtheir functions.5 hours

Unit 10AC.0: Revision unitRevision of key ideas from Grade 9.1 hour

Unit 10AC.1: Structure and bonding in matterStructures of atoms. Atomic and molecular masses.Chemical bonding. Equations. States of matter.11 hours

Unit 10AC.3: Chemical patterns: part 1Periodicity. Trends in the periodic table (period 3,groups I, II, VII, VIII). Transition metals. Reactivityseries of metals. Alloys.9 hours

Unit 10AB.3: Enzyme actionMechanism of enzyme action. Competitive and non-competitive inhibition. Factors affecting enzymeaction.6 hours

Unit 10AB.4: Human transport systemHeart structure and function. Double circulatorysystem. Blood vessels. Red blood cells.9 hours

Unit 10AP.0: Revision unitRevision of key ideas from Grade 9.1 hour

Unit 10AP.1: Handling physical quantitiesSI units. Precision and accuracy. Assumptions inproblem solving. Vectors and scalars.6 hours

Unit 10AP.2: Mechanics and kinematicsDisplacement, speed, velocity and acceleration.Motion graphs. Equations of uniformly acceleratedmotion. Effect of forces on an object. Combinationand resolution of forces. Frictional and viscousforces.8 hours

Unit 10AP.3: Properties of matterKinetic particle model. Differences between solids,liquids and gases. Pressure, freezing, changes ofstate. Thermal expansion. Density and pressure.Hydraulics. Flotation.9 hours

Unit 10AP.4: Waves and soundPulses and travelling waves. Longitudinal andtransverse waves. Wave equation and terminology.Production and nature of sound waves.Transmission and detection of sound. Standingwaves and resonance. Musical instruments.9 hours

Unit 10AC.2: The chemical industryPurification techniques. Properties and fractionationof air. Fractionation of petroleum. Hardness anddistillation of water. Halogens. Metal extraction.Environmental issues and recycling.11 hours


Science scheme of work: Grade 10 advanced units 179 hours2nd semester84 teaching hours

Unit 10AB.5: Human health and diseaseClassification of diseases and illnesses. Endemic,epidemic and pandemic diseases. Diet, lifestyle andhealth.6 hours


Unit 10AB.6: DNA and protein synthesisDNA structure and replication. The genetic code.Protein synthesis, mRNA and tRNA.6 hours

Unit 10AB.7: Inheritance and variationChromosomes in diploid and haploid cells. Gametesand sexual reproduction. Variation in populations.6 hours

Unit 10AC.4: pH and acidspH. Neutralisation, titrations and indicators, salts,buffers. Acids - Brönsted-Lowry theory.8 hours

Unit 10AC.5: Environmental chemistryCarbon, nitrogen and water cycles. Atmospheric andwater pollution. Controlling and reduction ofpollutants. The role of the oceans in climate control.Ozone depletion. Global warming.10 hours

Unit 10AC.6: Reaction kineticsFactors affecting the rate of a chemical reaction.Reaction rate and kinetic modelling. Catalysis.Equilibria and dynamic reactions. Activationenthalpies. Bond making and breaking.10 hours

Unit 10AB.8: Classification and ecologicalrelationshipsClassification of organisms. Food chains and webs.Energy flow in an ecosystem. Micro-organisms andrecycling. Nitrogen-fixing bacteria and mutualism.11 hours

Unit 10AP.5: Light and opticsReflection and refraction. Image formation. Longand short sight. Total internal reflection. Dispersion.8 hours

Unit 10AP.6: Electrostatics and magnetismCharging by friction. Forces between electriccharges. Electric fields. Magnetisation. Magneticfields of permanent magnets. Ferromagneticmaterials.7 hours

Unit 10AP.7: Current electricity andelectromagnetismCurrent and charge. Conductors, semiconductorsand insulators. Voltage and resistance. Resistors inseries and parallel. Electrical power. Internalresistance. Magnetic fields due to currents.Electromagnetic force. DC motor. Hall effect.12 hours



Unit 11AB.0: Revision unitRevision of key ideas from Grade 10.2 hours


Unit 11AB.1: Relating cell structures to functionMitochondria, ATP and the biochemistry of aerobicrespiration. Cell membrane structure and transport.7 hours

Unit 11AB.2: Transport systems indicotyledonous plantsVascular systems of plants. Movement of water,transpiration and translocation.4 hours

Unit 11AC.0: Revision unitRevision of key ideas from Grade 10.3 hours

Unit 11AC.1: Bonding in more detailIntermolecular forces. Dative bonding. Physicalproperties related to bonding type. Electron orbitals.9 hours

Unit 11AC.2: How much is there?Quantitative treatment of moles, molarity and molarvolume. Empirical and molecular formulaecalculations. PV = nRT.9 hours

Unit 11AB.3: Physiological regulation inmammalsHomeostasis. Thermoregulation. Oestrous cycle.Nervous and hormonal control systems.8 hours

Unit 11AP.0: Revision unitRevision of key ideas from Grade 10.1 hour

Unit 11AP.1: Forces and movementNewton's laws of motion. Mass and weight. Centreof gravity. Force, mass and acceleration. Inertial andgravitational mass. Momentum conservation in onedimension. Principle of moments.10 hours

Unit 11AP.2: Work, energy and powerWork, force and displacement. Kinetic and potentialenergy. Energy transfer and conservation.Efficiency. Power.7 hours

Unit 11AB.4: Human gas exchange system andhealthGas exchange structures and functions. Exercise,pulse rate and blood pressure. Lung diseases.Effect of smoking.9 hours

Unit 11AC.3: ElectrochemistryOxidation, reduction and oxidation numbers.Electrochemistry including cell potentials and thereactivity series, half-cells and standard electrodepotentials, quantitative calculations, fuel cells andassociated environmental issues.7 hours

Unit 11AP.3: Thermal physicsThermal energy transfer and equilibrium.Conduction, convection and radiation. Convectioncurrents and weather. Specific heat capacity andlatent heat.10 hours



Unit 11AB.5: Biological basis of inheritanceDNA structure and replication. The genetic code.Protein synthesis, mRNA and tRNA. Chromosomesand reproduction. Mitosis and meiosis. DNA, genesand gametes. Mutations. Monohybrid crosses.Genetic variation. Sex-linked characteristics.11 hours


Unit 11AB.6: Evolution by natural selectionPredation, disease and competition. Diversity andadaptation of species. Selective advantage. Naturalselection and isolation.4 hours

Unit 11AB.7: Ecological relationships andpopulationsFood chains, webs and pyramids of numbers.Energy flow through ecosystems. Interactionsbetween organisms. Factors limiting size ofpopulations.6 hours

Unit 11AC.4: Chemical patterns: part 2Chemistry of O, S, N, P, C, Si and transition metals.6 hours

Unit 11AC.5: Organic chemistryNomenclature, structure, bonding and shape ofalkanes, alkenes and arenes. Aliphatic electrophilicand nucleophilic addition and substitution reactions.Alcohols, halogen compounds, aldehydes andketones, carboxylic acids and their derivatives.Comparison of arenes and aliphatic compounds.Amines and amides.15 hours

Unit 11AC.6: Making and using chemicalsHaber process, nitric acid and fertilisers. Sulfur andthe contact process. Limestone and cement. Additionand condensation polymerisation. Fats and oils.Natural polymers.11 hours

Unit 11AB.8: Microbiology and biotechnologyViruses, bacteria and fungi. Micro-organisms inrecycling. Carbon and nitrogen cycles. Mutualisticrelationships. Micro-organisms in food production.Cell culture techniques. Genetic engineering andrelated moral and ethical issues.9 hours

Unit 11AP.4: Properties of wavesReflection and refraction. Refractive index and wavevelocity. Diffraction, superposition and interference.Doppler effect. Properties and nature ofelectromagnetic waves. Coherence. Polarisation oftransverse waves.9 hours

Unit 11AP.5: Electronic devicesCapacitors and diodes. Variable resistors and theiruse in potential divider circuits. Logic gates and truthtables. Switches and memory circuits.6 hours

Unit 11AP.6: Electromagnetic inductionProduction of induced e.m.f. Magnetic flux.Faraday's and Lenz's laws. Eddy currents. ACgeneration. The transformer.10 hours

Unit 11AP.7: Atomic and nuclear physicsRutherford scattering. Nuclear model of atom.Nuclear transformations. Nuclear decay and half-life.Properties of nuclear radiations. Uses ofradioisotopes. Nuclear fission and fusion. Cathoderay tubes.10 hours



Unit 12AB.0: Revision unitRevision of key ideas from Grade 11.3 hours


Unit 12AB.1: Biological energeticsBiochemistry of anaerobic and aerobic respiration.ATP structure and generation. Biochemistry ofphotosynthesis. Carbon-14 in study ofphotosynthesis.15 hours

Unit 12AB.2: Transport systemsBlood: structure and function. Tissue fluid andlymph. Blood groups and transfusions. Translocationand factors affecting transpiration. Xerophyticadaptations.12 hours

Unit 12AC.0: Revision unitRevision of key ideas from Grade 11.3 hours

Unit 12AC.1: The periodic tablePeriodicity in ionisation energy, electron affinity andelectronegativity. Properties, compounds and trendsin s, p and d block elements. Amphiprotic elements.17 hours

Unit 12AC.2: Rates of reactionRate and equilibrium constants. Rate equations.Arrhenius equation.10 hours

Unit 12AB.3: Control, coordination andhomeostasisEndocrine glands and hormone regulation. Structureand function of kidney. Water balance andtemperature regulation. Structure and function ofneurones and brain. Plant hormones.18 hours

Unit 12AP.0: Revision unitRevision of key ideas from Grade 11.3 hours

Unit 12AP.1: Gravity and circular motionCentripetal acceleration and force. Angular velocity.Gravitational field strength. Newton's law ofgravitation. Satellites in circular orbit. Energy of anorbiting satellite.10 hours

Unit 12AP.2: The nature of matterStress, strain, Young modulus, strength andstiffness. Surface tension and interparticle forces.Fluid flow and pressure. Kinetic particle model forreal and ideal gases. Ideal gas equation andabsolute zero. Relationships between pressure,molecular speed, kinetic energy and temperature inan ideal gas.15 hours

Unit 12AP.3: ThermodynamicsKelvin and Celsius temperature scales. First law ofthermodynamics: energy conservation.Thermodynamic systems: heat, work and internalenergy. Second law of thermodynamics: entropy anddisorder; efficiency of heat engines.11 hours

Unit 12AC.3: Acids and K valuesAcidity, titrations, pH, pKa, Kw, buffers. Ksp.7 hours



Unit 12AB.4: Human immune systemStem cells and monoclonal antibodies. Immunesystem and allergies. Active and passive immunityand vaccination. Antibiotics and bacterial resistance.Cholera, influenza, malaria and TB. Gene therapy.12 hours


Unit 12AB.5: Genetic inheritanceDihybrid crosses. Co-dominance and multiplealleles. Chi-squared test. Human Genome Project.Genetic fingerprinting, screening and counselling.9 hours

Unit 12AB.6: Ecological relationshipsAdaptations of animals to their environment.Population growth dynamics. Ecological succession.Biological control. Conservation and preservationissues.13 hours

Unit 12AC.4: Energy and entropyBorn-Haber cycles. Second law of thermodynamics.Standard entropy and free energy changes.16 hours

Unit 12AC.5: Organic reaction mechanismsShape of aliphatic organic compounds and electronicstructure. Electrophilic and nucleophilic reactionmechanisms.11 hours

Unit 12AC.6: Aromatic organic chemistryNomenclature, structure and bonding of aromaticcompounds. Arene chemistry. Mechanism ofelectrophilic substitution and factors affecting it.Nitroarenes, amines and azo-compounds.11 hours

Unit 12AB.7: BiotechnologyGenetically engineered human insulin. Biosensorsand blood glucose. Monoclonal antibodies.Immobilised enzymes.8 hours

Unit 12AP.4: OscillationsFree oscillations. Simple harmonic motion:equations and graphs for displacement, velocity,acceleration, potential and kinetic energy. Dampedand forced oscillations. Resonance.9 hours

Unit 12AP.5: Electrostatic charge and forceUniform electric field. Coulomb's law for pointcharges. Electric potential, field strength andpotential gradient. Electrical and gravitational fields.Capacitors: charge and energy; combination inseries and in parallel.13 hours

Unit 12AP.6: Quantum and nuclear physicsEmission and absorption spectra. Photoelectriceffect. Quantisation of electron orbital energy.Quantisation of electric charge. Wave-particleduality of electrons. Equivalence of mass andenergy. Schrödinger model of hydrogen atom.14 hours

Unit 12AP.7: Astrophysics and cosmologyThe visible Universe: stars and galaxies; scale andstructure. Very distant objects: look-back time;redshift; universal expansion; the Big Bang;spacetime. Formation and evolution of stars andplanets.15 hours

Unit 12AC.7: Making and using chemicalsEconomics of the alkali industry. Industrial processesversus environment. Exploitation of Qatar's naturalgas.7 hours

Unit 12AC.8: MacromoleculesStructure and function of amino acids, proteins,nucleotides and nucleic acids. Relationships betweenphysical properties of polymers and their structures.Polymer additives, plasticisers, foams.8 hours


3

Units of work: Grades 7 to 9

About the units Each teaching unit focuses on a group of standards. It outlines what teachers should teach, and how. It also indicates the approximate time that it would take to teach the work.

The title page

Each unit has a title page that gives:

• basic information about the unit;

• expectations for what students should achieve by the end of the unit;

• the main resources that will support the work in the unit (excluding textbooks and other learning resources that vary from school to school);

• key vocabulary or technical terms that students need to know and use.

The expectations on the title page can be used to review progress and check whether students are ready to move on to the next unit. They also provide a framework for giving feedback to students or reporting to parents.

Standards for the unit

The second page of each unit shows the standards for the unit. These form the teaching objectives for the unit. They are phrased for teachers, but could be reworded more simply and discussed with students at the beginning of a lesson or sequence of lessons.

The standards for the unit are set out in three columns.

• The centre column contains the relevant standards for the grade. These include all the relevant key standards and should be taught to all students.

• The left-hand column shows supporting standards that will help students who learn more slowly to consolidate what they know, understand and can do. Some of the supporting standards may be non-key or previously taught standards for the relevant grade, but mainly they are drawn from lower grades.

• The right-hand column shows extension standards that challenge more able students and extend what they know, understand and can do. Some of the extension standards may be non-key standards for the relevant grade, but mainly they are drawn from the subsequent grade or even higher grades.

The remaining pages of the unit

Each unit then describes briefly:

• teaching and learning activities, showing:

– how teachers can present the topic to students; – what activities students can do to develop or consolidate the relevant

knowledge, understanding and skills; • suitable questions that students can be asked during and at the end of a

topic to assess their learning. For Grades 7 to 9, these can be incorporated in informal class activities, given for homework or offered in a short test. From Grade 7, some of these assessments should include the use of a scientific calculator.

Space is left in each unit for teachers to add their own notes about which of the school’s learning resources can best support students’ work during the unit, including science apparatus, materials, relevant parts of workbooks or textbooks for students and ICT resources, such as computer software, data recording equipment and the Internet.


Number of units and teaching time

There are 16 units in Grade 7, 15 in Grade 8 and 18 in Grade 9. Units vary in length from 5 to 12 hours depending on the topic and provide a total of about 135 teaching hours per year for Grades 7 and 8 and about 180 in Grade 9. This leaves suitable time for revision and preparation for the national tests.

The units in each grade are grouped into four strands (life science, materials, Earth and space, and physical processes) corresponding to the four content strands of the science standards. Within each strand the units are numbered. The numbers reflect a suggested teaching order. For each strand there is a preliminary unit (numbered 0). These should be taught before the other units in each strand, normally in the first semester. The preliminary units are assumed to be revision of work covered in a previous grade. Each strand also has a review unit (unit R) that should be taught in semester two before any further units in a strand are undertaken. The review units should recap on the work of semester one and provide a preparation for new work.

The preliminary units and review units are not provided in this scheme of work since what science is selected for revision will depend on the school, the students and the teachers, but time is allowed in the overall teaching time for teaching the preliminary units and review units.

Creating lesson plans based on the scheme of work The teaching and learning activities described in each unit should help teachers to create their lesson plans for a block of lessons or individual lessons. The lesson plans should also take account of the formative assessments that teachers have been making as they have been teaching previous units. (For this reason, lesson plans cannot be finalised far in advance of the lessons.)

Each unit of work will require several lessons, for example, an 8-hour unit on electromagnetism may be divided into two blocks of lessons: one block dealing with electromagnets and the other with electric motors. Each block may consist of fours hours of work. One block of lessons may deal with electromagnetic effects, making and using electromagnets and investigating

the effect of different core materials. The other block may deal with the uses of electric motors, making an electric motor and investigating factors affecting the running of an electric motor.

The objectives for each individual lesson based on the unit are likely to address some but not all of the objectives for the units. The objectives may be repeated in more than one lesson, and may appear again in a subsequent unit.

As with the scheme of work, there is no right or wrong way to set out a lesson plan. The main criterion is that it helps a teacher to teach the lesson.

Typically, lesson plans will indicate:

• the objectives for the lesson or block of lessons;

• relevant vocabulary and technical terms;

• the resources needed, such as apparatus, materials, textbooks and ICT applications;

• any safety concerns;

• how the lesson will start;

• how work will be developed through teaching input and student activities, with suggestions for differentiation where appropriate;

• how lessons will be summarised and rounded off;

• homework, where relevant.

The last lesson of each unit will require a more extended review or summary of the unit as a whole. This review can be based on the expectations described on the unit’s first page. This is the time to draw out the key learning points and what students need to remember. The review should highlight the ways in which the unit has built on previous learning, the progress that students have made and what students will go on to learn next. Where appropriate, links can be made to work in other units and to applications in ‘real life’ or at home.


Integrating scientific enquiry Every unit in the Qatar scheme of work for science encourages the use of ‘hands-on’ practical activities and provides opportunities for students to develop the skills of scientific enquiry. While every unit addresses content standards, appropriate learning activities are cross-referenced to the scientific enquiry standards.

A number of units list scientific enquiry standards among the core objectives of the unit in order to emphasise their importance.

It is crucial that the scientific enquiry strand of the science standards is not forgotten and that activities to allow students to acquire scientific enquiry skills are incorporated into teachers’ lesson plans.

Incorporating the use of ICT Possible activities in which students use information and communication technology (ICT) are shown in the scheme of work. For example, teachers in Grades 7 to 9 could select from these possible uses of ICT for their science lessons.

• A digital camera to capture images, record observations and make displays.

• Simulations and computer games that help to reinforce students’ basic knowledge and understanding.

• Calculators, when used to carry out calculations, to allow students to focus on the appropriateness of the procedure and the patterns in the answers rather than on the correctness of the arithmetic.

• The Internet as a source of information.

• Datalogging equipment to record experimental or environmental data over time in a form that can be processed by a computer.

• Video or CD-ROM to illustrate phenomena.

• Simple spreadsheets and databases to allow students to enter data, compile statistics and produce a range of graphs, charts and tables. Students can decide on the most appropriate way to display data, and can readily make and test hypotheses about the impact of a change in the data set.

• An interactive whiteboard to enter and display information. (An interactive whiteboard is a hardware device combining the functions of a monitor and keyboard of a computer. It acts as a large display and is also touch sensitive. Information is entered by touching specific areas of the screen.)

• PowerPoint to create useful presentations. Slides can be sequenced to give the impression of a moving object or a film.

Opportunities to use ICT are indicated in the units.

Useful websites for science in Grades 7 to 9

The Internet can be used as a source of relevant information for teachers and students. There are websites that give teachers more background to the science they are teaching, websites offering suggestions for use in class and websites that provide activities for students. The Internet also allows students to exchange scientific data and ideas with others around the world. A selection of useful websites is listed below.

• www.scienceonestop.com/ range of teaching resources from the UK Association for Science Education

• www.scienceacross.org/index.cfm?fuseaction=content.showhomepage range of opportunities for links with science across the world

• www.schoolscience.co.uk range of free teaching resources

• scienceonline.co.uk Internet resource for science teachers

• www.learn.co.uk subscription site of learning resources

• www.standards.dfes.gov.uk/schemes2/secondary_science/ schemes of work with ideas for learning and teaching activities

• vtc.ngfl.gov.uk virtual teachers’ centre with many resources and teaching plans

• activescience-gsk.com interactive modules, databases and worksheets


• www.matter.org.uk/ support for learning and teaching about matter

• www.nutrition.org.uk/ support for learning and teaching about nutrition

• www.bbc.co.uk/education.ks3bitesize range of short learning activities

• www.kapili.com/physics4kids/ range of physics materials

• biologycorner.com/ resource site for biology teachers with lesson plans and classroom activities

• echalk:Science free resources for teachers to use with interactive whiteboards and data projectors

• tre.ngfl.gov.uk/ teacher resource-exchange website with science-based teaching resources and ideas

• www.educationusingpowerpoint.org.uk site with PowerPoint presentations on many topics

• hop.concord.org/ hands-on physics website with many ideas for investigations with inexpensive apparatus

• bio/Itsn.ac.uk/imagebank freely available bioscience images

• www.cite-sciences.fr/ French site with several simulations

• www.phy.ntnu.edu.tw/java/ series of Java applets with animations and simulations

• www.booolean.ca/perlib downloadable periodic table and activities

• www.creative-chemistry.org.uk/ worksheets, PowerPoints and ideas for practical work

• www.whyfiles.org illustrations and information on a wide range of science topics

• www.badphysics.info/ explanations of commonly misunderstood phenomena

• www.tryscience.com practicals to do on computer and then in the lab

• www.fearofphysics simulations, video clips and quizzes to help explain ideas in physics

• www.science.howstuffworks.com/ explanations

• www.data-harvest interfacing and data capture resources

• philipharris.co.uk interfacing and data capture resources

• www.omarfoundation.org/Culture/History%20Science.htm science information on Islamic science

Language objectives It is important to teach students the content-specific vocabulary and technical terms associated with each scientific topic. Relevant words are listed on the first page of each unit.

Science teachers should reinforce the speaking and listening strategies taught in Arabic and English lessons, including skills such as asking for information, giving advice, agreeing and disagreeing. Teachers should also promote higher-order language skills by expecting students to describe their observations and explain and justify their conclusions and investigative approaches to each other. Paired work and group work to discuss and evaluate ideas are as essential in science lessons as they are in language lessons.

Similarly, science lessons should promote students’ reading strategies, since these are crucial for accessing information in books and on the Internet, and for identifying key information for scientific enquiry. As students get older,


there should be increasing attention to information-gathering strategies, inference and deduction.

Writing is an important means of communicating scientific information. Science lessons should include opportunities for informal writing in the form of journals or learning logs and more formal report writing involving the whole cycle of drafting, revising and redrafting.

Catering for more able students, or students who are making slower progress In all science classes there will be a spread of ability and attainment. Teachers need to plan lessons to keep all students involved and suitably challenged. This will include arranging appropriate support to help any students who have fallen behind to catch up.

When teachers are planning questions for the whole class, they should allow enough waiting time for students to think, or to discuss the question with a partner, before answering. Open questions enable more students to respond. Questions can also be directed to individuals or groups of students in line with their abilities.

The main way of catering for a range of attainment in science classes is through differentiated group activities. Planning of a unit of work might take account of three groups: most students, students who have progressed further and students who have not made as much progress.

Some students work faster than others because they are generally more confident and more able. They need extension or enrichment tasks and activities. Others may need longer to practise and consolidate what they have been learning and need examples at each level of difficulty. The units in the scheme of work contain a few suggestions for extension and consolidation activities, but in general these will need to be drawn from related units in the next grade or an earlier grade.

Students in a class do not all need to do every question or task associated with every learning activity. When teachers are planning activities for students to do, they should select appropriate questions and tasks to give to each of the three main groups of students.

Homework provides another opportunity to set suitably challenging tasks.

Students who are exceptionally able

The science standards are targets for the majority of students in a grade. Exceptionally able students deal with abstract science more readily than other students. They will have progressed more quickly through the standards for the primary grades. In Grades 7 to 9, they should follow a programme that increasingly draws on the standards for a higher grade.

They will also need extension and enrichment activities to develop the breadth of their science knowledge and understanding and the depth of their scientific thinking. This challenging work should require them to demonstrate extensive understanding and more advanced knowledge and skills, and can be continued at home. As in the earlier grades, students would derive considerable benefit from carrying out personal projects at an after-school science club and participation in science fairs and competitions.

Students who have fallen behind

Some students in Grades 7 to 9 may have fallen behind the expected standards for their age because of their circumstances. Some may have minor learning difficulties, or misconceptions remaining from earlier work. Some may have been moved to a number of different schools, or have gaps in learning resulting from missed or interrupted schooling. Some may have been disadvantaged by circumstances at home. These students need opportunities to catch up.

Additional support for them is of great benefit, either in extra timetabled lessons or in after-school sessions. The programme that they follow will need to be based on a diagnosis of their weaknesses or misconceptions about the work in earlier grades and to build in some extra consolidation. Schools may also be able to encourage parents to help their children in specific ways.


Teaching science in the medium of English The expectation should be that, as far as possible, students who are taught science in English should progress in their scientific learning at the same rate as students who are taught in Arabic. However, there are potential difficulties to overcome.

One danger is that students taught in English spend most of the time on practical work to avoid reading and writing. Another is that a teacher who is not completely fluent in English may have difficulty explaining a scientific concept, confuse students through the misuse of a scientific term, or lose the pace of a lesson through hesitancy with words. Students have many alternative conceptions about established concepts in science. Teachers are challenged to help them reconsider their understandings. Working in a second language adds to the challenge.

The suggestions in the next few paragraphs can help to minimise some of these difficulties.

Speaking and listening

Whole-class work can provide helpful models of spoken English. In any oral work, it helps to use objects and demonstrations, provide extra visual clues or gestures, and give a translation wherever necessary. Teachers will need to direct specific instructions to students and may need to speak more slowly. They will also need to emphasise key words, particularly when they are describing tasks or activities that students will do independently or in groups.

Whenever possible, teachers should show objects, demonstrate phenomena and techniques, and use diagrams and illustrations to help to illuminate meaning and ease understanding.

When students are working in groups, teachers will again need to give specific instructions and to speak more slowly. Key words should be stressed, particularly when describing tasks that the group is to do. Extra visual clues or gestures, or translation, can also be used.

Peer-group talk helps students to make sense of and apply scientific ideas. During group work, students should use Arabic for informal discussions.

Reading and writing

Students should be taught the specific scientific vocabulary needed for each unit of work in both English and Arabic, including common chemical names and mathematical signs and symbols such as % and π. There should be frequent opportunities to refer back to this vocabulary in oral questioning.

Teachers can stress scientific vocabulary in wall displays. If appropriate, these can be illustrated with diagrams and/or pictures. These displays can be referred to in the beginnings and ends of lessons and while teaching.

Wherever possible, teachers should read through and discuss with the class any questions or exercises from textbooks that they ask students to do, and demonstrate carefully how students should record their scientific work.

Students in Grades 7 to 9 should also be introduced to the way that mathematical and scientific calculations and equations and scientific arguments would be recorded in Arabic.

Science units Grade 7

Contents

7L.1 Specialised cells 45 7M.1 Particulate nature of matter

81 7P.1 Measurement and density 119

7L.2 Human reproduction 51 7M.2 Mixtures compounds and elements

87 7P.2 Electrostatics 127

7L.3 Variation 57 7M.3 Combustion 95 7P.3 Magnetism 133

7L.4 Growing plants 63 7M.4 Acidity 103 7P.4 The effects of forces 141

7L.5 Soil 69 7E.1 Origins and properties of rocks

111 7P.5 Electrical circuits 149

7L.6 Food webs 75

45 | Qatar science scheme of work | Grade 7 | Unit 7L.1 | Life science 1 © Education Institute 2005

GRADE 7: Life science 1

Specialised cells

About this unit This unit is the first of six units on life science for Grade 7.

This unit is designed to guide your planning and teaching of lessons on life science. It provides a link between the standards for science and your lesson plans.

The teaching and learning activities should help you to plan the content and pace of lessons. Adapt the ideas to meet the needs of your class. For extension or consolidation activities, look at the scheme of work for Grade 8 and Grade 6.

You can also supplement the activities with appropriate tasks and exercises from your school’s textbooks and other resources.

Introduce the unit to students by summarising what they will learn and how this builds on earlier work. Review the unit at the end, drawing out the main learning points, links to other work and 'real life' applications.

Previous learning To meet the expectations of this unit, students should already know that cells are the fundamental building blocks of living organisms and that some cells are structured for specialised functions. They should already know that cells have cytoplasm, a nucleus and a cell membrane and that plant cells have a cell wall. They should be able to label a diagram of a typical plant cell and a typical animal cell. They should already be able to use a simple microscope correctly.

Expectations By the end of the unit, students describe and draw typical animal and plant cells, know the function of cell structures and relate the functions of specialised cells to their structures. They know that cells form tissues and organs. They use a microscope, prepare a slide and examine objects such as root hairs and leaf structure.

Students who progress further describe the structure and function of plant cells involved in photosynthesis.

Resources The main resources needed for this unit are: • microscopes with low and high power lenses • microscope that can project an image onto a screen • prepared slides of a variety of plant and animal tissues • glass slides and cover slips, scalpels, forceps, plant material

Key vocabulary and technical terms Students should understand, use and spell correctly: • microscope, magnification • cell membrane, cytoplasm, nucleus, cell wall, chloroplast, vacuole • xylem, phloem, palisade, epidermis • unicellular, multicellular

UNIT 7L.1 7 hours



7 hours SUPPORTING STANDARDS CORE STANDARDS

Grade 7 standards EXTENSION STANDARDS

6.5.1 Know that living organisms are made up of cells.

6.5.2 Know that cells have cytoplasm, a nucleus and a cell membrane and that plant cells have a cell wall.

7.7.1 Describe and draw typical animal and plant cells; know that cells are the basic building blocks of organisms and form tissues and organs.

8.10.1 Describe the structure and function of plant cells involved in photosynthesis.

6.5.3 Know that some cells are structured for specialised functions.

6.5.4 Know that collections of cells with the same function form tissues (such as muscle) and that organs (such as the stomach) are made of tissues of different types.

7.7.2 Recognise and know the function of the cell nucleus, cell membrane, cytoplasm, vacuole and cell wall, and relate the overall structure of some specialised cells (e.g. nerve cells, sperm cells, xylem cells, palisade cells) to their functions.

6.3.4 Use a simple microscope.

3 hours

Animal and plant cell structure and the function of parts of a cell

2 hours

Specialised cells, tissues and organs

2 hours

Making model cells

6.2.3 Draw carefully labelled diagrams that show relationships, processes and observations.

7.4.5 Prepare a microscope slide correctly; use a microscope to examine objects such as leaf surfaces and root hairs.

Unit 7L.1


Activities

Objectives Possible teaching activities Notes School resources

Review with students that all living things are made of cells and that plant and animal cells are different. Ask students to sketch and label a typical plant and animal cell to see how much they remember from Grade 6. Discuss the function of nucleus, cytoplasm, cell membrane and cell wall. Introduce and explain the terms chloroplast and vacuole to complete the labelling of a plant cell.

Ask students to identify which parts of a cell are common to plant and animal cells, and which parts only plant cells have. Challenge students to explain why plant cells have a cell wall, vacuole and chloroplasts and how animal cells manage without these cell parts.

Ask students to draw annotated diagrams of a typical plant and animal cell in the form of a mind map with drawings, cartoons and notes to help them remember the function of each part (e.g. draw a sun shining over chloroplasts to remember photosynthesis occurs within them).

Use this column to note your own school’s resources, e.g. textbooks, worksheets.

Remind students how to use a microscope safely and how to focus correctly. Demonstrate to students how to draw microscope images by using a microscope that can project an image onto a screen. Give students a diagram with lots of deliberate errors (e.g. incorrect shading, blurred lines, wrong magnification and labels) and ask them to identify all the mistakes.

Provide students with a variety of different slides of plant and animal cells. Ask them to draw one or two cells from a slide and label the drawing with magnification and any parts of a cell they can see clearly.

A microscope that can be projected onto a screen is very useful for demonstrations.

Prepare a suitable diagram. Students will need: compound microscopes with a range of objective lenses (×10, ×20 and ×40) and a range of prepared slides.

3 hours

Animal and plant cell structure and the function of parts of a cell Describe and draw typical animal and plant cells…

Recognise and know the function of the cell nucleus, cell membrane, cytoplasm, vacuole and cell wall…

Prepare a microscope slide correctly; use a microscope to examine objects such as leaf surfaces and root hairs.

Show students how to prepare thin sections of plant material to make their own slides (e.g. transverse section of a leaf). Also prepare epidermis plant material (e.g. onion, leaf surface, petal) and whole mounts of moss and Elodea (pondweed). Ask students to look at chloroplasts of Elodea under high-power magnification – they may see cytoplasmic streaming and chloroplasts moving towards a light source.

Encourage students to show each other some of their best slides so that they can assess each other’s work and provide each other with feedback.

Ask students how plants cells from roots are different from leaf cells.

Students will need: compound microscopes with a range of objective lenses (×10, ×20 and ×40), glass slides and cover slips, scalpels, forceps, plant material.

Enquiry skill 7.4.5

Unit 7L.1



Show students diagrams and microscope images of single-celled plants and animals. Ask students to use the Internet or reference books to research the detail of these organisms (e.g. how a paramecium, dinoflagellate or amoeba moves and feeds). Show students a labelled diagram of Euglena and ask students to list how Euglena is like an animal and how it is like a plant. Introduce the term protist to describe these difficult to classify unicellular organisms.

Explain to students that all life processes have to happen within one cell for a unicellular organism and ask them to suggest possible advantages of being multicellular.

Collect images of unicellular organisms to show to students.

ICT opportunity: Use of the Internet.

2 hours

Specialised cells, tissues and organs … know that cells are the basic building blocks of organisms and form tissues and organs

Remind students of the specialised cells they found out about in Grade 6. Explain how specialised cells are organised into layers of tissue, organs and organ systems. Ask students to draw branching diagrams to show how different plant and animal organ systems include different organs and that these organs are made of different tissues of specialised cells (e.g. circulatory system – heart, arteries and veins – blood, cardiac, elastic tissue – muscle, red blood cells and white blood cells).

Show students a simple model of an animal cell and a plant cell. Challenge students to make a model at home of a plant or animal specialised cell. Encourage students to use their imagination and make the model as close as they can to the specialised cell (e.g. make a red blood cell by pouring red jelly into a mould and wrap it in plastic – just like a red blood cell this model is flexible, biconcave and has no nucleus).

Ask some students to present their model to the class, explaining how the cell is specialised, what each part of the model represents and the function of each part of the cell. Choose four models for the whole class to evaluate: ask them to discuss how the models are accurate (e.g. three-dimensional) and what their limitations are (e.g. cell membrane does not allow some substances to pass through).

Use a clear plastic bag of cellulose paste with a small black ball in it to model an animal cell. To model a plant cell, add some smaller green balls and use an ice pop to represent the vacuole; put the bag inside a box.

2 hours

Making model cells … and relate the overall structure of some specialised cells (e.g. nerve cells, sperm cells, xylem cells, palisade cells) to their functions.

Extension activity Ask students to use the Internet to research the answer to the question ‘Are red blood cells alive?’ Tell them to present their research as a list of features that suggest that a red blood cell is alive (e.g. part of a multicellular organism) and a list of features that suggest that it is not alive (e.g. cannot move or reproduce). Scientists cannot agree on the answer to this question, and it is a useful example of uncertainty in science.

ICT opportunity: Use of the Internet


Assessment

Examples of assessment tasks and questions Notes School resources

Assessment Set up activities that allow students to demonstrate what they have learned in this unit. The activities can be provided informally or formally during and at the end of the unit, or for homework. They can be selected from the teaching activities or can be new experiences. Choose tasks and questions from the examples to incorporate in the activities.

The diagram shows two plant cells.

Cell X Cell Y (not to scale) a. In which part of a plant would these cells be found?

Cell X

Cell Y

b. Give the name of part B.

c. (i) Give the letter which labels the nucleus.

(ii) What is the function of the nucleus?

d. How can you tell from the diagram that photosynthesis cannot take place in cell Y?

Adapted from QCA Year 9 science test, 2000

Grade 7 students carried out an experiment to find out why cells are so small. They put different sized clear jelly cubes into purple dye for 20 minutes. The students then cut each cube in half to see how far the dye had been absorbed. Here are their results:

a. Describe what these results show.

b. Name a substance that a cell would need to absorb to stay alive.

c. If cells were too large, what would happen to the centre of the cell?

Unit 7L.1



Human reproduction

About this unit This unit is the second of six units on life science for Grade 7.


The teaching and learning activities should help you to plan the content and pace of lessons. Adapt the ideas to meet your students’ needs. For extension or consolidation activities, look at the scheme of work for Grade 8 and Grade 6.


Introduce the unit to students by summarising what they will learn and how this will build on earlier work. Review the unit at the end, drawing out the main learning points, links to other work and 'real life' applications.

Previous learning To meet the expectations of this unit, students should already understand the changes that occur during puberty to enable reproduction. They should already know when to use bar charts and line graphs and how to interpret such graphs.

Expectations By the end of the unit, students know the basic anatomy of the human reproductive system. They know about human reproduction and about the growth, development and birth of a baby. They know the importance of good nutrition during pregnancy and the importance of good nutrition and hygiene to the health of babies. They use secondary evidence and information critically.

Students who progress further distinguish between sexual and asexual reproduction.

Resources The main resources needed for this unit are: • diagrams of reproductive systems, pregnancy and birth • video or software animation to show fertilisation and implantation • large netting (e.g. badminton net) • small pieces of card labelled oxygen, nutrients, carbon dioxide, waste

products and nicotine; large pieces of card labelled red blood cells and bacteria.

• ultrasound scan images, photographs and diagrams of developing foetus • data on mass and size of developing foetus

Key vocabulary and technical terms Students should understand, use and spell correctly: • gamete, ovulation, fertilisation, implantation • oviduct, ovary, uterus, vagina, testis, penis • embryo, foetus, amniotic fluid, placenta, umbilical cord

UNIT 7L.2 8 hours





6.7.1 Understand that during puberty the body changes to enable reproduction and that this also results in the development of secondary sexual characteristics.

7.8.1 Know the simple anatomy of the human female and male reproductive systems; know the basic facts about human reproduction and about the growth, development and birth of a baby.

7.8.2 Know the importance of good nutrition during pregnancy and of good nutrition and hygiene to the health of babies.

7.1.2 Use secondary evidence and information selectively and critically. 8.1.6 Search for, select and make critical use of secondary information sources, such as sources on the Internet.

3 hours

Male and female reproductive systems

2 hours

Pregnancy, development and birth of a baby

3 hours

Care of a newborn baby

6.2.2 Know when to use bar charts and when to use line graphs to represent discontinuous and continuous data and be able to interpret such graphs.

7.3.1 Use a range of methods, such as description, diagrams, pictures, tables, graphs and calculations, using ICT methods where appropriate, to communicate observations, data, results and conclusions.

8.3.1 Present qualitative and quantitative data using a range of methods, such as descriptions and tables and through pictures, graphs and diagrams, using ICT methods where appropriate, and draw conclusions from them.

Unit 7L.2


Activities


Begin the unit by telling students that if they have any questions about human reproduction they should write them anonymously on paper and hand them in so that any misconceptions can be addressed during the unit.

Define sexual reproduction as the formation and fusion of two gametes or sex cells and ask students what these sex cells are in animals and what they are in plants. Provide students with diagrams of the male and female reproductive system to label. Establish that sperm are produced in testes and eggs in ovaries.

Remind students of work on cells and establish that, for fertilisation to occur, a male cell (sperm) fuses with a female cell (egg). Explain that, for many animals that live in water, fertilisation takes place externally, whereas for humans and other animals that live on land, fertilisation takes place inside the female’s body.

Provide diagrams for students to label.


Talk with pupils about the egg travelling down the oviduct and sperm being deposited in the vagina and moving to where an egg is. Use video or software animation to show this.

Explain fertilisation in terms of the fusion of nuclei of sperm and egg. Discuss what happens next – that the fertilised egg grows and divides to produce more cells. Ask students to put the stages of human reproduction into the correct sequence: ovulation, fertilisation, cell division and implantation. Ask students to draw or annotate a set of diagrams to illustrate these steps. Check that students can correctly indicate on a diagram where fertilisation takes place.

3 hours

Male and female reproductive systems Know the simple anatomy of the human female and male reproductive systems; know the basic facts about human reproduction and about the growth, development and birth of a baby.

Discuss what students know about the length and stages of pregnancy. Define the terms embryo and foetus and explain the role of the amniotic fluid, placenta and umbilical cord. Use a large piece of netting (with about 4 cm width holes) to model the placenta’s role as a filter between the blood of mother and foetus. Give students small pieces of card labelled oxygen, nutrients and water to pass through the netting placenta from mother to baby and carbon dioxide and waste products to pass from baby to mother. Also include a small card labelled nicotine to highlight the risks of smoking when pregnant. Give students some larger pieces of card labelled red blood cell and bacteria and show that these are too big to pass through the placenta.

Unit 7L.2



Use photographs, models, diagrams and ultrasound scans to look at how the foetus changes and develops during pregnancy.

Provide students with data about the mass of the embryo and foetus each month of pregnancy and ask students to plot this information as a line graph. Ask students to carefully describe the shape of this graph and how the rate of growth of the foetus changes (e.g. the rate of growth is very slow in the first 16 weeks of pregnancy).

Ask students to predict the shape of a similar graph for length of foetus and think carefully about any differences they might expect. Ask students to plot data on length of foetus as a line graph or provide students with the line graph. Compare this graph with the graph of change in mass of the foetus.

Enquiry skill 7.3.1

Discuss with students the processes of labour and birth, using diagrams to illustrate these. Check that students understand: that contractions of the uterus muscles push the baby out; that the afterbirth is the placenta; what happens to the umbilical cord. Explain that sometimes a natural delivery is not possible and women have a caesarean section.

2 hours

Pregnancy, development and birth of a baby … know the basic facts … about the growth, development and birth of a baby.

Use a range of methods, such as description, diagrams, pictures, tables, graphs and calculations, using ICT methods where appropriate, to communicate observations, data, results and conclusions.

Extension activities Ask students to use the Internet to research the care of premature babies – why do they often need help feeding and breathing? Relate this to the function of the placenta during pregnancy and ask students why the lungs of a baby born at 30 weeks are underdeveloped.

Review the process of human reproduction with a true–false quiz bringing in points raised by students’ anonymous questions at the start of the unit.


Enquiry skill 7.1.2 Prepare questions for a true–false quiz.

Ask students to consider what a woman should eat during pregnancy using their knowledge of what food groups, vitamins and minerals are needed for growth and development of bones.

Challenge students to research the nutritional needs of a pregnant woman using reference books and the Internet. Ask them to select the most useful information and summarise their findings as an advice leaflet. This could include food and drink that evidence suggests women should not eat during pregnancy (e.g. raw shellfish).


Enquiry skill 7.1.2

Ask students how newborn babies obtain food. Provide students with the detailed composition of breast milk, including vitamins and minerals to show it is a complete balanced diet. Compare this composition with that of cow’s milk – how is it different? Why is the composition different?

Provide students with packaging from formula milk and baby food and ask them to analyse the nutritional composition. Discuss how a baby’s dietary needs are different from an adult’s.

Collect nutritional information about breast milk and cow’s milk, and packaging from formula milk and baby food.

Enquiry skill 7.1.2

3 hours

Care of a newborn baby Know the importance of good nutrition during pregnancy and of good nutrition and hygiene to the health of babies.

Use secondary evidence and information selectively and critically.

Ask students to discuss in small groups what they know about the care of newborn babies and to agree on a top ten list of what a baby needs. Encourage students to think of all aspects of care: nutrition, hygiene, education, sleep, etc.

If possible, invite a nurse into class to discuss care of a newborn baby and answer students’ questions.


Assessment


Complete the table below to compare the male and female reproductive systems:

Male Female

Sex cells

Organs where sex cells are made

Tubes sex cells travel down

Opening to the outside

Label the diagram of pregnancy and correctly match up the function of each part in the table.

Part of pregnant woman Function

Uterus Connects foetus to placenta, transporting nutrients to the foetus and removing waste products.

Placenta Acts like a cushion, protecting the foetus.

Umbilical cord Allows substances to pass between the blood supply of mother and foetus.

Amniotic fluid Contains the developing foetus, blood vessels provide nutrients.

Provide students with a diagram to label showing a foetus developing inside a woman’s uterus.


The bar chart shows the percentage of premature and low birthweight babies that have birth defects. a. What effect does low birth weight have on the percentage of babies born with

birth defects?

b. What effect does premature birth have on the percentage of babies born with birth defects?

c. Which babies are at highest risk of birth defects, those with low birth weight or born prematurely?

<2500 g >2500 g

Source: Shaw et al, 2001, www.cbdmp.org/ ef_pregnancy.htm

Unit 7L.2



Variation

About this unit This unit is the third of six units on life science for Grade 7.





Previous learning To meet the expectations of this unit, students should already recognise that characteristics can vary between members of the same type of organism. They should be able to conduct systematic investigations, make predictions from and identify patterns in data and observations, and consider whether evidence supports a conclusion, prediction or hypothesis.

Expectations By the end of the unit, students distinguish between environmental and inherited variation. They know that selective breeding creates organisms with desirable characteristics. They plan investigations, make predictions, collect data and make observations in a systematic way, identify patterns, and draw appropriate generalised conclusions and test predictions.

Students who progress further know that sexual reproduction is a major source of genetic variation and know the nature of a clone. They plan, collect data and make observations in a systematic way, identify patterns, consider the validity of evidence, the extent to which it supports a prediction, and draw conclusions.

Resources The main resources needed for this unit are: • plant trays, oat seeds, soil and other growing mediums • photographs of different breeds of dogs • information about breeding racing camels

Key vocabulary and technical terms Students should understand, use and spell correctly: • inherited, environmental characteristics, selective breeding • pollination, artificial insemination

UNIT 7L.3 7 hours





5.4.2 Know that individual members of the same type of organism show variation.

7.5.1 Know that some features of organisms are inherited while others are determined by their environment.

9.5.1 Distinguish between sexual and asexual reproduction; know that sexual reproduction is a major source of genetic variation in animals and plants, while a clone produced by asexual reproduction has the same genetic materials as its parent and will be identical.

7.5.2 Know that selective breeding can produce organisms with desirable characteristics.

6.1.1 Plan investigations, controlling variables and collecting an appropriate range of evidence, identify patterns in observations and data, draw appropriate generalised conclusions and test predictions.


8.1.1 Plan investigations, controlling variables and collecting an appropriate range of evidence, using appropriate techniques to ensure accuracy, identify patterns in observations and data, draw generalised conclusions and test predictions.

2 hours

Inherited and environmental variation

2 hours

Investigate what affects the height of seedlings

3 hours

Selective breeding

7.1.4 Understand the importance of accuracy and use techniques such as repetition of measurements to ensure it.

8.1.4 Take representative samples during large investigations and decide how many measurements are required for the results to have an acceptable reliability.

Unit 7L.3


Activities


Ask students ‘What would happen if we were all the same? What would the world be like?’ Encourage them to think about all the advantages and disadvantages. If it is not mentioned, ask ‘What would happen if we were all exactly the same and a new disease emerged that could kill us?’ Use this thought experiment to help explain why variation is so important for our survival.

Ask students how this variation is caused. Explain that there are two causes of variation: inherited and environmental. Encourage students to make a list of features that are inherited from their parents (e.g. eye colour). Remind them about the function of the nucleus of a cell and that, when the nucleus of an egg and a sperm fuse, this brings together genetic information from mother and father. This means that we inherit a mixture of characteristics, which increases variation further.


2 hours

Inherited and environmental variation Know that some features of organisms are inherited while others are determined by their environment.

Ask students to discuss and write a list of features that can be affected by the environment (explain that the environment includes accidents, which may cause scars). Describe a fable about the features of an animal; for example, how the elephant got its trunk – a crocodile pulled the elephant’s nose when it went to drink in the river. Ask students if this fable could be true – could an elephant with a stretched nose pass on the characteristic to its offspring?

Now discuss characteristics that are inherited and affected by the environment (e.g. height).

Expect some students to have misconceptions about acquired characteristics and allow time for them to think this through and realise that it cannot be true (e.g. if you lost your finger in an accident you would not have a child with a finger missing).

Set students the problem ‘What affects the height of oat seedlings?’ First discuss all the possible variables that could affect the height of the seedlings. Allow groups to choose different variables to investigate and plan how they will carry out their investigation. Encourage students to make sensible decisions about how often they will take measurements, how many seeds they will need in order to collect enough evidence and what their control will be (e.g. to grow 20 seedlings in the sun and 20 in the shade to see what effect light has on growth).

Students will need: plant trays, oat seeds, soil and other growing mediums.

Enquiry skills 7.1.1, 7.1.4

2 hours

Investigate what affects the height of seedlings Plan investigations, controlling variables and collecting an appropriate range of evidence, identify patterns in observations and data, draw appropriate generalised conclusions and test predictions.

When students have collected sufficient measurements of their seedlings (over 2 or 3 weeks) ask them to describe what their evidence shows. Encourage them to discuss why the height of the seedlings varies in terms of inherited and environmental factors. Ask them whether the variation of height of seedlings in one condition is greater or less than that between different conditions.

Point out to students that many other characteristics important to growing oats as a crop are not as easy to measure (e.g. resistance to disease).

Unit 7L.3



Provide students with photographs of a variety of different breeds of dogs. Ask them to list the characteristics of dogs that are similar between breeds (e.g. large canine teeth and good sense of smell) and the characteristics that are different (e.g. coat colour and thickness, leg length). Compare the adult size of a Chihuahua (3 kg and 15 cm tall) and a Irish wolfhound (70 kg and 90 cm tall).

Dogs have been selectively bred through the centuries for special purposes (e.g. to pursue and retrieve game, as guides dogs for the blind and as companions). Ask students how all these different breeds came about and how breeders get the right kind of puppy. Encourage students to write their own account of how a breed of dog may have been developed over many years by selecting parents with the right characteristics. Ask students to use reference books or the Internet to research the origins of the Arabian saluki, which has been bred for thousands of years for speed and has wide paws to enable it to run on sand.


Explain to students that modern domesticated animals have all been bred by humans to have desirable characteristics. Ask what characteristics may have been desirable in breeding sheep, cattle and goats.

Explain to students how a plant breeder transfers pollen from one flower to another to breed plants with specific characteristics. Ask what characteristics may have been desirable in breeding tomatoes, strawberries, onions and carrots.

3 hours

Selective breeding Know that selective breeding can produce organisms with desirable characteristics.

Ask students to use reference books or the Internet to research selective breeding for racing camels. Tell them to present the information as a booklet that includes: • characteristics that are desirable for racing camels; • how camel breeders use artificial insemination and embryo transfer to produce a faster

camel; • environmental factors that can affect the success of a racing camel (e.g. diet and training).


Enquiry skill 7.1.4


Activities


There is a variety of tomato that has yellow skin. When two yellow tomato plants are bred, the seeds grow into plants that produce yellow tomatoes.

a. How is the characteristic yellow skin passed on in tomatoes?

b. List two environmental factors that could result in different sized yellow tomatoes.


The table below gives a list of characteristics of a Grade 7 student. Complete the table to show whether the characteristic is inherited, affected by the environment or both.

Characteristic Inherited Environmental Both

Boy

Weight 550 N

Brown eyes

Good at football

Brown hair

1.7 m tall

Can speak English

Here are some characteristics of camels:

• lean and lightweight;

• heavy build and muscular;

• large hump;

• small hump;

• tall;

• produces a lot of milk.

People breed camels for different purposes.

a. Choose two of the characteristics above that would be desirable for a racing camel. Give reasons for your answers.

b. Choose two of the characteristics above that would be desirable for a camel for transport. Give reasons for your answers.

Suggest one other characteristic that breeders of both types of camel would want their camels to have.

Unit 7L.3



Growing plants

About this unit This unit is the fourth of six units on life science for Grade 7.




Introduce the unit to students by summarising what they will learn and how this builds on earlier work. Review the unit at the end, drawing out the main learning points, links to other work and ‘real life’ applications.

Previous learning To meet the expectations of this unit, students should already know that green plants make their own food. They should know the parts of flowering plants responsible for anchorage (roots), circulation (xylem and phloem), gas exchange (stomata), food production (leaves and stem) and waste removal (stomata).

Expectations By the end of the unit, students describe how water and nutrients enter and pass through a plant, and know that nitrogen and other nutrients are required for plant growth. They plan investigations, make predictions, collect data and make observations in a systematic way, identify patterns, and draw appropriate generalised conclusions and test predictions. They use a microscope, prepare a slide and examine objects such as root hairs and leaf structures.

Students who progress further describe the structure and function of plant cells involved in photosynthesis. They know that green plants make their own food by photosynthesis, which requires light and the chlorophyll in chloroplasts, together with water and carbon dioxide, and that oxygen is produced. They consider the validity of evidence, the extent to which it supports a prediction, and draw conclusions.

Resources The main resources needed for this unit are: • selection of different seeds (e.g. cress, beans, oats, grass) • containers or seed trays and growth mediums (e.g. potting compost, peat,

inert growth mediums such as rock wool, sand, perlite) • shoots of various plants, dye, scalpel, prepared slides of transverse

sections of stems and leaves, microscope with low- and high-power objective lenses

• plants with growing root systems (e.g. spring onions, garlic, germinating mung beans or cress), video clip of roots growing

• leafy plant and plastic bag • two-coloured carnation flower prepared by splitting the stem lengthways

and placing the two halves in water containing different coloured dyes • video clips and/or photographs of large-scale fertiliser application to

farmland • a selection of labels from packaged fertilisers • Internet access, spreadsheet programme (e.g. Excel)

Key vocabulary and technical terms Students should understand, use and spell correctly: • nutrients, minerals, fertiliser, nitrates • xylem, phloem, transpiration

UNIT 7L.4 7 hours





7.9.1 Describe how water and nutrients enter a root hair and pass up through a plant.

6.6.3 Know the parts of flowering plants that are responsible for anchorage (roots), circulation (xylem and phloem), gas exchange (stomata), food production (leaves and stems), reproduction (flowers) and waste removal (stomata).

7.9.2 Know that nitrogen and other nutrients are required for plant growth.

8.10.2 Know that green plants make their own food by photosynthesis and that water and carbon dioxide are required and oxygen is produced.



8.1.1 Plan investigations, controlling variables and collecting an appropriate range of evidence, using appropriate techniques to ensure accuracy, identify patterns in observations and data, draw generalised conclusions and test predictions.

3 hours

Water and nutrient uptake in plants

2 hours

Nutrients required for plant growth

2 hours

Measure the effect of a nitrogen based fertiliser on plant growth

6.1.2 Consider the extent to which evidence justifies a conclusion or supports a prediction or hypothesis.


8.1.2 Consider the extent to which the evidence justifies a conclusion or supports a prediction or hypothesis, and identify further investigations that might be needed.

Unit 7L.4


Activities


Review what students already know about the structure of plants from Grade 6. Ask students to explain the function of the roots, stem and leaves of a plant. They should recall that there are two different transport tubes in a plant: xylem to transport water and phloem to transport dissolved sugars. Roots have two functions, to anchor the plant and to take in water.

Explain to students that roots also take in minerals that are dissolved in the water. Make sure students understand that these nutrients are not food for the plant. An investigation to look at later in the unit needs to be set up at this stage so that it can be monitored over a number of weeks. Provide students with a choice of different seeds (e.g. cress, beans, oats, grass) and ask them to plan an investigation to find out what effect adding fertiliser will have on the plants. Provide a choice of growth mediums (e.g. potting compost, peat and inert growth mediums such as rock wool, sand, perlite). Allow students to work in groups and make their own decisions about the containers, seeds and growth medium they use, also how much fertiliser they add and how often they measure the effect of the fertiliser. Some groups may choose to modify their plan over the next few weeks.

Safety: Be careful when perlite is dry, as the dust is an irritant. Perlite should be handled wearing a mask or moistened before use.

Enquiry skill 7.1.1


Provide students with plants with growing root systems (e.g. spring onions, garlic, germinating mung beans or cress). Challenge them to find out how roots are adapted for taking in water and ask them to look closely at the roots using a hand lens and a microscope. If available, show a video clip of roots growing. Remind students of the specialised cells they studied at the start of Grade 7 and ask them to draw and describe how root hair cells are specialised for absorbing water. A simple way to explain this is to draw the outline of a typical plant cell and a root hair cell, follow the outline in string, then compare the length of string to show how much greater the surface area of the root hair cell is. (Students do not need to know about osmosis at this stage.)

There is a short clip of root hairs growing at www.bio.davidson.edu/misc/movies/root.mov

Enquiry skill 7.4.5

3 hours

Water and nutrient uptake in plants Describe how water and nutrients enter a root hair and pass up through a plant.

Plan investigations, controlling variables and collecting an appropriate range of evidence, identify patterns in observations and data, draw appropriate generalised conclusions and test predictions.

Show students a carnation flower that is dramatically one half red and one half blue and ask students how they think you have made this happen. They may correctly suggest that you have split the stem and placed the two halves in different coloured dyes. Ask students to place various cut shoots of plants in dyed water for a few hours then cut thin transverse sections to observe xylem tubes with a microscope. Provide students with prepared slides of transverse sections of stems and leaves to see that xylem tubes are present in both.

Summarise for students that water enters the roots and travels up the stem and ask where it goes next. Students should be able to explain that water is used in photosynthesis by the leaves. Remind them that leaves have tiny holes in them called stomata for gas exchange. Explain that water also evaporates from leaves and this is called transpiration. Demonstrate this by placing a leafy plant in good light. Cover some of the leaves in a clear polythene bag and make a seal. Students can observe the water from transpiration gather on the sides of the bag.

Prepare a two-coloured carnation flower in advance by splitting the stem lengthways and placing the two halves in water containing different coloured dyes.

Safety: Students must take care when using scalpels.

Enquiry skill 7.4.5

Unit 7L.4



Recap with students that plants use carbon dioxide and water in photosynthesis to make sugars. Explain that for plants to make other substances, in particular proteins, they need other elements. Ask students why they need to eat proteins as part of their diet and establish that proteins are important for growth. Explain that plants also need proteins to grow – the difference is that instead of eating proteins, plants make them. Ask students where plants get these minerals from.

Ask students to think through what will happen to the soil of a field over a number of years if a farmer grows a crop every year and adds nothing to the soil. Also ask them to think about how well the crops grow each year. Explain that the mineral content of the soil will become very low, crops will fail to grow and this is why farmers add fertiliser to the soil. Provide a selection of labels from packaged fertilisers so that students can look at the minerals that they contain – in particular nitrates. Explain the term NPK fertiliser – it means that the fertiliser contains compounds that contain the elements nitrogen, phosphorous and potassium.

Ask students to summarise information about the nutrients plants need as a table, describing the role each nutrient plays in the life of the plant. Tell them the cost of a pack of fertiliser, and the recommended application rate, and ask them to calculate the cost per 100 square metres of crop. Show students video clips or photographs of large-scale fertiliser application to farmland. Ask students whether there is any alternative to using expensive fertilisers; they may suggest using organic fertilisers.

Mathematics: Calculating cost of fertiliser per 100 square metres.

Enquiry skill 7.3.1

2 hours

Nutrients required for plant growth Know that nitrogen and other nutrients are required for plant growth.

Extension activity Ask students to use the Internet or reference books to research carnivorous plants (e.g. Venus fly trap, sundew and pitcher plants). These plants eat insects; challenge the students to find out why. (Most of these plants live in highly acidic wetland habitats low in soil nutrients and eat insects to compensate for the low availability of nutrients.)




2 hours

Measure the effect of a nitrogen based fertiliser on plant growth Know that nitrogen and other nutrients are required for plant growth.


The students’ fertiliser investigation continues over a number of weeks. Ask them to take measurements of their seedlings as they grow and record their results in a table. Some students may only be measuring the height of the plant, while others may also be measuring the size and number of leaves.

Once students have collected sufficient results, possibly over 6 weeks, get them to input their data on a spreadsheet so that they can produce different types of graphs and look for patterns in their results.

Explain to students how to evaluate their investigation. For example, is there a significant difference between the seeds grown with and without fertiliser? Groups who chose to grow beans or used potting compost may find that there is very little difference. Ask students if they have any unexpected or anomalous results – some groups may have added too much fertiliser or not enough water and their plants did not grow well.

Students can learn a great deal about what makes a good investigation by comparing the results they obtained and conclusions they drew with those of other groups. Explain to groups whose results do not show any clear patterns that they have learnt a lot about effective planning rather than failed the investigation. Ask each group to present their findings and their evaluation of their investigation. After each presentation, ask the rest of the class to provide constructive feedback about the group’s investigation. Ask the whole class which type of seeds and which growth medium produced the most reliable results and to design an improved investigation. Explain that research scientists carry out small-scale trials like this to check their experimental design.

Enquiry skill 7.3.1

ICT opportunity: Use of spreadsheet software.


Assessment


Plants take in water from the soil. Nada did an experiment to find out whether there is anything else in soil that plants need for growth. The diagrams of flasks A and B show the results of Nada’s experiment.

Nada made the clear, brown solution in flask B by shaking a mixture of soil and water and then separating the solution from the soil particles

a. How could Nada separate the brown solution from the soil particles?

b. Explain why Nada grew one plant in distilled water.

c. i. What type of substance, dissolved in the water in flask B, is used by the plant for growth?

ii. How are roots adapted for taking in water?

d. Nada set up a second experiment using three similar plants. The solution in flasks C, D and E was the same. She put all three flasks in a sunny position. The diagrams show the results of Nada’s second experiment.

The plant in flask C was the only one which grew well in this experiment. Explain why.

Adapted from QCA Year 9 science test, 1999


Two Grade 7 students explain why plants have roots:

Rabab says ‘Plants get food through their roots.’

Omar says ‘Plants only take in water through their roots.’

Both students’ answers are not quite correct. Write a fuller and more detailed explanation of why plants have roots.

Unit 7L.4


Grade 7: Life science

Soil

About this unit This unit is the fifth of six units on life science for Grade 7.





Previous learning To meet the expectations of this unit, students should already know that individual micro-organisms are too small to see with the unaided eye. They should know that micro-organisms can be harmful and cause illness or food poisoning.

Expectations By the end of the unit, students understand the importance of micro-organisms in nitrogen fixation, decomposition and nutrient recycling. They use a microscope, prepare a slide and examine objects such as roots.

Students who progress further can give examples of the use of micro-organisms in food production.

Resources The main resources needed for this unit are: • samples of alfalfa with roots and root nodules, hand lenses, microscopes • legume seeds, inert growth medium (e.g. perlite or vermiculite), distilled

water, nitrogen-free nutrients, Rhizobium (sometimes known as ‘Inoculum’)

• mixture of leaves and vegetable peelings, clear sealed container • video clips of time-lapse photography showing organic matter

decomposing • Internet access

Key vocabulary and technical terms Students should understand, use and spell correctly: • fertiliser, alfalfa, Rhizobium, root nodules, legume • decay, decomposition, compost, sewage treatment

UNIT 7L.5 6 hours



6 hours SUPPORTING STANDARDS

CORE STANDARDS Grade 7 standards

EXTENSION STANDARDS

7.10.1 Know that specialised bacteria in the soil and in the roots of some plants fix atmospheric nitrogen.

6.10.1 Know that if left unprotected, most foods will be contaminated by micro-organisms in the air and become unfit to eat.

7.10.2 Know that micro-organisms in soil decompose organic matter and dead organisms and help to recycle nutrients.

8.11.1 Know that micro-organisms are used in making foods such as bread, cheese and yoghurt.

3 hours

Specialised bacteria in soil and root nodules fix atmospheric nitrogen

3 hours

Micro-organisms in soil decompose organic matter and recycle nutrients

6.3.4 Use a simple microscope. 7.4.5 Prepare a microscope slide correctly; use a microscope to examine objects such as leaf surfaces and root hairs.

Unit 7L.5


Activities


Ask students what helps plants to grow well and discuss the factors they suggest. Remind them of the investigations they carried out on the effect of adding fertiliser in Unit 7L.4 and that fertilisers contain nitrogen. Provide the following information from a soil and water quality specialist: ‘Applying nitrogen fertiliser to good alfalfa stands is not recommended.’

Tell students that alfalfa is the oldest and most important forage crop in Qatar and worldwide. It is grown to feed livestock and originated in Asia around 2700 years ago. Challenge students to find out why alfalfa does not need fertiliser. Provide some samples of alfalfa, including their roots. Ask students to make careful observations of alfalfa roots using a hand lens and microscope. Encourage students to prepare their own slides of root nodules or to look at images or prepared slides on high-power magnification. Alfalfa roots have root nodules containing Rhizobium bacteria; ask students what they think Rhizobium may be doing so that alfalfa does not need nitrogen fertiliser.

Ask students what percentage of the air is nitrogen. Explain that plants cannot access this nitrogen directly through their leaves and that Rhizobium bacteria convert nitrogen gas in the soil into a form of nitrogen that the plant can use. Add that there are other bacteria in the soil that fix nitrogen.

Students have already learnt that farmers can use nitrogen fertilisers to add nutrients to soil, but these can be expensive. If a farmer ploughed up a field of alfalfa there would be enough nitrogen for a subsequent crop of corn. Explain that alfalfa is a legume and other legumes that are important crop plants also have root nodules (e.g. clover, soybean, pea, bean, chickpea, lentil). Discuss with students why legumes are such important crop plants, particularly in developing countries.

Enquiry skill 7.4.5


Extension activity Encourage students to use reference material or the Internet to find out more about alfalfa cultivation in Qatar and about crop rotation, a technique farmers used to use of growing a cycle of different crops each year so that nutrients in the soil were not depleted.


3 hours

Specialised bacteria in soil and root nodules fix atmospheric nitrogen Know that specialised bacteria in the soil and in the roots of some plants fix atmospheric nitrogen.

Prepare a microscope slide correctly; use a microscope to examine objects such as leaf surfaces and root hairs.

If possible, allow students to investigate the effect root nodules have on plant growth. Provide students with legume seeds, inert growth medium (e.g. perlite or vermiculite), distilled water, nitrogen-free nutrients and Rhizobium (also known as ‘Inoculum’). Let them grow plants for 4–6 weeks and measure height or mass to see whether there is a significant difference between plants with Rhizobium root nodules and a control group.

Safety: Be careful when perlite or vermiculite is dry as the dust is an irritant. Either moisten them before use or make sure students wear masks.

Enquiry skill 7.1.1

Unit 7L.5



Remind students that plants need to take in nutrients from the soil in order to grow well; ask where these nutrients come from in a natural habitat, where there are no fertilisers. Students may suggest that decaying organic matter and waste release nitrogen compounds. Explain that the process of decay also involves micro-organisms – bacteria and fungi.

Demonstrate the effect soil micro-organisms have on decomposition. Collect a mixture of leaves and vegetable peelings. Put half this mixture into a clear sealed container. Bury both samples next to each other in the school grounds and leave for several weeks. Dig up the two samples and ask the students to compare them.

Show students video clips of time-lapse photography showing organic matter decomposing and emphasise that this is how nutrients are returned to the soil. Ask students to design a compost bin – this needs to be well insulated and covered, but should also allow water and air to circulate. Ask students to annotate their designs with explanations of each design feature.

3 hours

Micro-organisms in soil decompose organic matter and recycle nutrients Know that micro-organisms in soil decompose organic matter and dead organisms and help to recycle nutrients.

If possible, arrange a visit to a sewage works, or a visit from a scientist who works there, to discuss how micro-organisms play a vital role in sewage treatment. Alternatively, there are many websites that show diagrams and descriptions of sludge treatment and production of methane gas in sewage works.

Ask students to summarise how legumes and soil micro-organisms are involved in the recycling of nutrients in a diagram.

Visit opportunity: Visit a local sewage treatment plant.


Enquiry skill 7.3.1


Assessment


Advice on building a compost bin lists four critical factors for decomposition to take place.

The critical factors are:

• air;

• moisture;

• nitrogen materials;

• time.

For each factor, explain why it is important. Refer to micro-organisms in your answer.


Here is a diagram to show how nutrients are recycled.

Describe what happens at A, B, C and D.

Unit 7L.4



Food webs

About this unit This unit is the sixth of six units on life science for Grade 7.





Previous learning To meet the expectations of this unit, students should already know that organisms within a habitat have feeding relationships and that green plants are the basis of many food chains.

Expectations By the end of the unit, students construct food chains and food webs and know why human and environmental change can alter a food web. They manipulate observations and data and use tables, graphs and ICT methods to communicate them.

Students who progress further can construct and interpret a pyramid of numbers and biomass. They process electronically logged data in appropriate ways.

Resources The main resources needed for this unit are: • sets of cards to use to construct food chains (see text for details) • pooters and containers for insects, field guides and identification keys • electronic dataloggers and sensors for temperature, amount of light,

oxygen and humidity • Internet access, presentation software (e.g. PowerPoint)

Key vocabulary and technical terms Students should understand, use and spell correctly: • producer, primary consumer, secondary consumer, tertiary consumer • plankton, food web, ecosystem, community, habitat

UNIT 7L.6 8 hours



8 hours SUPPORTING STANDARDS

Including Grade 5 and 6 standards

CORE STANDARDS Grade 7 standards

EXTENSION STANDARDS Including Grade 8 standards

8.5.1 Relate changes in numbers of organisms in a habitat to their feeding relationships.

5.5.1 Know that some organisms in a habitat feed off green plants, others prey on other animals and some eat dead animals.

5.5.2 Know that green plants make their own food.

7.6.1 Construct food chains and food webs.

8.5.2 Interpret pyramids of numbers and biomass representing the organisms linked in a food chain.

7.6.2 Know why human action and environmental change can alter a food web.

7.2.1 Know that scientists work by looking for patterns in data, building conceptual models that explain the patterns.

4 hours

Construct food webs and chains from different ecosystems

4 hours

How human impact and environmental change alter food webs

6.2.2 Know when to use bar charts and when to use line graphs to represent discontinuous and continuous data and be able to interpret such graphs.


8.3.3 Process electronically logged data in appropriate ways and draw conclusions from them.

Unit 7L.6


Activities


Review the work students did on food chains in Grade 5. Organise students into groups and give each group a set of cards to use for making a marine food chain (see Notes). The organisms might be: plant plankton (microscopic plants), animal plankton (microscopic animals), sardines and sailfish. Ask students to make the food chain, discussing the task as they do so: this involves placing the organisms in the correct order, arranging the arrows connecting the organisms so that the arrows point in the right direction, and finally adding the label producer or consumer to each organism. Check that groups have placed their arrows in the correct direction and clarify with students that the arrows in a food chain mean ‘is food for’ and point from the food to what eats it. Explain that animals that eat plants (e.g. animal plankton) are called primary consumers as they are the first animals in the food chain. Also explain the terms secondary and tertiary consumer.

Ask students to draw their food chain in the centre of a large piece of plain paper. Now provide students with information about a second marine food chain. This might state that shrimps also eat plankton and are eaten by squid, which are food for bottlenose dolphins (who also eat sardines). Ask students to add these animals to their diagram and draw arrows to make a food web. Introduce more organisms found in the Arabian Sea (e.g. anchovies, green turtles, sea weed) for students to add to their food web.

Prepare suitable sets of cards for making food chains. Four of these will contain a picture and the name of four different organisms: a producer, a primary consumer, a secondary consumer and a tertiary consumer. There should also be one card with the word producer written on it, three cards with the word consumer written on them, and three arrows.


Explain to students the term ecosystem as a living community that depends on each member and its surrounding environment. Explain that the living part of an ecosystem is called a food web and the different place each organism lives is a habitat. Some animals and plants share the same habitat, and some organisms are a habitat for others e.g. the insects and moss that live on a tree. Students may find it useful to make a glossary for this topic as there are a number of new terms.

Provide students with a food web of a different ecosystem (e.g. desert) and ask them to write out food chains from this food web of three or four links. Also provide a list of organisms from a food web and what they eat and ask students to construct the food web.

Ask students to think about why food chains rarely have more than five links. This question should raise the issue of energy flow through food chains. Ask what happens to the energy stored in the food an animal eats. Encourage students to consider that a small amount of energy is transferred into new body mass of the animal, some is left in undigested waste, and most of it is used for processes such as keeping warm and moving about. This is why there are so few tertiary consumers in an ecosystem. (Students look at pyramids of numbers in Grade 8.)

4 hours

Construct food webs and chains from different ecosystems Construct food chains and food webs.

Know that scientists work by looking for patterns in data, building conceptual models that explain the patterns.

If possible, organise field work in a local habitat (e.g. school grounds, sand dunes, park) and discuss with students the questions they will try to answer during their work. These should include: • What lives here? • How can I measure the sizes of populations of living things? • Why are the animals and plants found here different from the ones found elsewhere?

Field work opportunity: Visit a local habitat.

Unit 7L.6



Ask students for their ideas about the data they will collect to answer their questions. Show them different ways of safely collecting animals for identification (e.g. using a pooter). Tell them to take digital photographs of plants rather than removing them. Challenge students to identify the plants and animals they observe using field guides and keys.

ICT opportunity: Use of a digital camera.

Safety: Make sure that students are careful handling living organisms and do not damage the habitat they are collecting animals from.

Ask students to find out what each animal they find eats so that they can construct a food web of the organisms they find.

Qatar has a number of conservation projects so, if possible, arrange a visit from an ecologist or environmental scientist to tell students about how they gather evidence. Encourage students to use their own experience to prepare questions.


Provide students with a food web and challenge them to predict the effects of making changes to the numbers of one type of organism. Encourage them to go beyond simple relationships by considering knock-on effects of a single change. For example, in the marine food web, if the number of shrimp decreases because of over-fishing, there will be more plankton, providing more food for sardines and anchovies, whose numbers may increase as a result. However, a smaller shrimp population may result in fewer squid, so bottlenose dolphins eat more sardines, and their population decreases.

Provide students with scenarios about changes in a number of different places and ask them to consider the immediate and long-term changes in populations of different communities.

Remind students that an ecosystem consists of living parts, in the form of communities of plants and animals, and non-living parts Students can measure and investigate characteristics of these non-living parts (e.g. temperature, amount of light, pH of soil or water, dissolved oxygen in water, humidity). using electronic dataloggers. Ask students to take measurements of a habitat and look for patterns (e.g. more plant species grow in the shade where the soil retains more moisture). Ask students to produce graphs from the data collected and interpret these graphs and write conclusions.

ICT opportunity: Use of electronic dataloggers

Enquiry skill 7.3.1

4 hours

How human impact and environmental change alter food webs Know why human action and environmental change can alter a food web.


Ask students to use the Internet or reference material to research how changes in the environment can alter a food web. For example, they could: • find out how a rise in sea temperature to 37 °C caused coral bleaching in the Arabian Gulf

and what effect this loss of coral had on the reef food web; • research how oil spills damage marine food webs or how acid rains affects the forests and

lakes of some countries; • look at data about fish stocks and fish catches in the Arabian Gulf over a number of years –

get them to discuss the possible reasons why the species and quantities of fish caught changes over time.

Ask students to present their findings using PowerPoint. Their presentation should include: • a description of the ecosystem they studied – the living and non-living parts; • an example of a food chain or food web from the ecosystem; • how human action or environmental change has affected the ecosystem.

ICT opportunity: Use of the Internet. Useful information on coral bleaching can be found at www.ameinfo.com/41072.html

ICT opportunity: Use of PowerPoint.


Assessment


The diagram below shows part of a food web in the Arabian desert.

a. Fox population studies show that the number of sand foxes has increased from 1995 to 2005. What effect will this have on the numbers of other animals in the food web?

b. From the food web, give the name of:

i. a producer;

ii. a primary consumer;

iii. a tertiary consumer.

c. Write a complete food chain with four links that ends with sand fox.


There are interactive assessment activities on the Internet that challenge students to place organisms into a variety of food webs, for example:

• www.harcourtschool.com/activity/food/food_menu.html

• www.vtaide.com/png/foodchains.htm

Unit 7L.6

jerboa

81 | Qatar science scheme of work | Grade 7 | Unit 7M.1 | Materials 1 © Education Institute 2005

GRADE 7: Materials 1

Particulate nature of matter About this unit

This unit is the first of four units on materials for Grade 7.

The unit is designed to guide your planning and teaching of lessons on materials. It provides a link between the standards for science and your lesson plans.




Previous learning To meet the expectations of this unit, students should already recognise and be able to describe the characteristics of the three states of matter.

Expectations By the end of the unit, students classify materials as solid, liquid or gas, and describe, and cite evidence for, the characteristic movement of particles in a solid, a liquid and a gas. They explain the observed shape and volume of samples of gases, liquids and solids. They explain common observations related to gas pressure, solution, diffusion, thermal expansion and changes of state, in terms of the motion of particles. They develop a qualitative concept of the size of particles of matter. They make and test predictions. They know that scientists work by building conceptual and testable models and they use laboratory glassware and heat sources safely.

Students who progress further explain more complex observations such as the Brownian movement in terms of particle collision, explain commonly observed energy changes associated with phase change and the compression and expansion of gases, and conduct experiments to estimate a maximum size of some particles. They understand the need for accuracy and know how to achieve it.

Resources The main resources needed for this unit are: • standard chemistry laboratory glassware and hardware • common laboratory chemicals • atomic models • computer-generated models of particle behaviour • lesson plan 7.2

Key vocabulary and technical terms Students should understand, use and spell correctly: • freeze, melt, boil, condense, evaporate, diffuse, crystallise • expand, contract, compress • particle • predict • miscible, immiscible

UNIT 7M.1 10 hours



10 hours SUPPORTING STANDARDS CORE STANDARDS Grade 7 standards

EXTENSION STANDARDS

4 11.1 Know that there are three states of matter – solid, liquid and gas – and that each state of matter has particular characteristics.

7.11.1 Know that solids remain the same volume and shape, that liquids remain the same volume but take up the shape of the container, and that gases expand to fill any container they are placed in.

4.11.6 Know and demonstrate that air is a material and that it fills spaces between solids.

4.11.1 Know that there are three states of matter – solid, liquid and gas – and that each state of matter has particular characteristics.

7.11.2 Know of, and cite evidence for, the movement of particles in solids, liquids and gases, and draw diagrams to represent particles in solids, liquids and gases; know that this process is called diffusion.

7.11.3 Explain, in terms of the particle model, a variety of common phenomena, such as thermal expansion, gas pressure, the compressibility of gases (but not liquids and solids) and the regular growth of crystals in a saturated solution.

7.11.4 Cite evidence for the existence and size of particles. 8.12.1 Know that the smallest particle of an element is an atom and that atoms of one element are of one kind and are different from atoms of every other element.


1 hour

Recall the different characteristics of solids, liquids and gases

1 hour

Distinguishing between solids, liquids and gases

3 hours

Interpreting experimental evidence

4 hours

Explaining observed phenomena using the particle model

1 hour

Estimating the size of particles

7.2.1 Know that scientists work by looking for patterns in data, building conceptual models that explain the patterns.

UNIT 7M.1


Activities

Objectives Possible teaching and learning activities Notes School resources

Recall work from earlier grades (particularly Grade 4) on the differences between solids, liquids and gases, and their main characteristics. Explore these characteristics further through a number of short demonstrations or group activities.

Show how a finely divided solid, such as sand or flour can be have very much like a liquid. Show what happens when the containers holding these solids are tilted. Show that both flour and water will go through a sieve but only water will go through a coffee filter paper. Discussion of this should lead to the idea of a difference in particle size.

All these activities can be carried out with everyday equipment.

Bottled gas can be used instead of natural gas.

Safety: The flammability of natural or bottled gas should be demonstrated by the teacher unless the class has been trained to use the Bunsen burner.

Enquiry skill 7.1.1


Find the volume of air that can be squeezed out of a sponge under water. Collect the gas in an inverted jar and compare its volume with the volume of the sponge.

Show examples of other gases, such as carbon dioxide in a fizzy drink and natural gas (methane). Note that although they look the same they may have different properties; demonstrate that natural gas is flammable. Open a drink can in a bucket of water and collect the carbon dioxide.

Show that some liquids, such as methylated spirits and water, are miscible, but others, such as cooking oil and water, are not. Investigate the miscibility of different liquids, such as methylated spirits and cooking oil.

1 hour

Recall the different characteristics of solids, liquids and gases Know that solids remain the same volume and shape, that liquids remain the same volume but take up the shape of the container, and that gases expand to fill any container they are placed in.

Recall work on changes of state by group work or demonstrating the effect of heating and cooling on three states of water. Ensure that the terms melting, freezing, boiling and condensing are understood.

Safety: The boiling of water and the condensation of steam should be demonstrated.

Carry out a classification exercise using common materials to ensure that students are familiar with the terms solid, liquid and gas. This will build on and recall work done on the three phases in Grades 4 to 6.

Ask students to work in groups and to discuss the classification of a number of substances. Some of these substances should be easy to classify while others should be difficult, like toothpaste, tomato sauce, baking powder, jelly. One should be a gas, but it could be a pressurised container, such as an air freshener, that contains a liquid but produces a gas. Ask groups to list the properties of solids, liquids and gases and perhaps also develop a key to distinguish them.

Link to work on keys in life science Grade 6 (Standard 6.4.1).

No special equipment is needed for this activity.


1 hour

Distinguishing between solids, liquids and gases Know that solids remain the same volume and shape, that liquids remain the same volume but take up the shape of the container, and that gases expand to fill any container they are placed in.

In front of the class tear a piece of paper in half. Then tear one of the halves in half, then one of the quarters in half. Carry on until you have a very small piece. Invite students to speculate on whether you could do this indefinitely if you had small enough hands, or whether you would reach the point where you had a single particle of paper that you could not divide in two. Ask them, in groups, to use their ideas to explain differences between solids, liquids and gases and for evidence for and against the concept of particles in solids, liquids and gases. At this stage do not present the particle theory yourself.

Unit 7M.1



Ask students to work in groups to perform a variety of short investigations, such as those in the list below, that will illustrate that solids, liquids and gases behave differently. • Show that the volumes of 1 kilogram of a number of different solids are different. • Try the ball and ring experiment. • Place a small coloured crystal of a soluble solid (such as potassium manganate(VII)) at the

bottom of a beaker of water. Leave it for some minutes. Move the water gently. • Depress the plungers of syringes filled with a solid, a liquid and a gas • Suspend an increasing number of masses from a nylon thread or thin wire until it breaks • Turn on the gas briefly (or open a bottle of perfume) and ask the class when they can smell it.

Tell students to discuss in their groups what has happened and to try to suggest explanations. Ask the groups to present their explanations to the other groups. Encourage a discussion between the groups. Make a list of the ideas and explanations that most groups agree on.

Present the theory that all matter is made up of particles (if students have not already suggested it). Ask groups to develop explanations for the phenomena they have observed by thinking of what happens to the particles. Ask them to think of alternative theories of matter – such as the theory that matter is continuous – that can explain the phenomena they have observed.

Safety: The ball and ring experiment requires the use of a Bunsen burner. Students should not use this until they have been trained in its safe use (enquiry skill 7.4.4).

Enquiry skills 7.1.1, 7.2.1, 7.2.3, 7.4.4

3 hours

Interpreting experimental evidence Plan investigations, controlling variables and collecting an appropriate range of evidence, identify patterns in observations and data, draw appropriate generalised conclusions and test predictions.

Know that scientists work by looking for patterns in data, building conceptual models that explain the patterns.

Ask students to make predictions, based on the particle theory, about what might happen in further investigations, such as if a coloured crystal or coloured water is placed on top of a colourless jelly, or if an inflated balloon is released.

Summarise the process students have gone through in a flow chart: make observations → propose theories → select the theory that accounts for most observations → use the theory to predict experimental results → if necessary, modify the theory in the light of the results.

Such prediction activities can provide useful assessment opportunities. See possible assessment activities at the end of this unit.

Ask students, in groups, to carry out a number of diffusion experiments, some of which can be left for a day or two and then examined. These can include activities such as: • Place a coloured crystal on the top of a some agar gel in a test-tube. • Using a long dropping pipette, carefully place a layer of concentrated copper sulfate solution

(or ink) below some water in a test-tube. • Burn a small piece of magnesium and watch what happens to the smoke.

Demonstrate the diffusion of nitrogen dioxide through a filter paper placed between two beakers, the top one inverted.

Safety: Appropriate safety precautions should be taken when burning magnesium, and students must be aware of the danger of looking directly at the flame.

Nitrogen dioxide is poisonous; its diffusion should be demonstrated in a well-ventilated space or fume cupboard.

Ask students, in groups, to take two measuring cylinders full to the 50 cm3 mark with water and pour into a 100 cm3 measuring cylinder. Tell them to repeat the activity with methylated spirits in one of cylinders. Explain the results. This can be illustrated with a model mixing the same volume of pebbles and sand.

4 hours

Explaining observed phenomena using the particle model Know of, and cite evidence for, the movement of particles in solids, liquids and gases, and draw diagrams to represent particles in solids, liquids and gases; know that this process is called diffusion.

Explain, in terms of the particle model, a variety of common phenomena, such as thermal expansion, gas pressure, the compressibility of gases (but not liquids and solids) and the regular growth of crystals in a saturated solution.

Ask students to grow crystals of a suitable salt, such as copper sulfate, aluminium potassium sulfate or chromium potassium sulfate. Explain, using models, the regular structure of crystals.

Demonstrate the ease of cleavage of a crystal to give parallel sides and ask for explanations in terms of particle layers. Show cleavage using a crystal model.

Make a collection of different crystals to show the variety of regular shapes that they can form.

Large crystals need to be grown over several weeks. Try variations (e.g. growing an aluminium potassium sulfate crystal using a chromium potassium sulfate seed). Crystals of common salt can be attempted but they are difficult. Crystals of Iceland spar, particularly suitable for cleavage, can be bought.



Simulate particle movement to show the effect of heat on a solid as it warms up, changes to a liquid and ultimately to a gas. This can be done in a variety of ways. Three-dimensional simulations of the effect of heat on particles are available on the Worldwide Web. Mechanical models are available that show the effect of increased vibration of ball-bearings. The class themselves can simulate particles subjected to heat.

ICT opportunity: Use of simulations. Lesson plan 7.2

Clarify the difference, in terms of particle energy and movement, between boiling and evaporation by demonstrating and discussing the two processes. Advanced students can consider the distribution of kinetic energy within particles of liquid at a given temperature and so understand why hotter water evaporates faster than colder water.

Extension work for faster students More advanced students can study the Brownian movement using a specially constructed smoke cell under a low-power microscope. Students often find this confusing because they are unable to draw a distinction between the particles of matter, which are invisible under the microscope, and the smoke ‘particles’ they see vibrating, which are in fact small pieces of solid that are collections of millions of particles

Another demonstration for advanced students is the bromine diffusion demonstration. Details of this demonstration are widely available and usually accompany the special equipment required to carry it out. This is a very effective way of demonstrating how fast gas particles actually move by comparing the diffusion of bromine through air at atmospheric pressure and in an evacuated vessel.

Safety: This experiment requires the use of a pump to evacuate specially constructed glassware and the use of bromine as a gas. A safety screen is essential. It should not be attempted by an inexperienced teacher.

The oil film experiment Estimate the volume of an oil drop on the end of a wire, using a magnifying glass and a ruler with 0.5 mm divisions. Touch the drop on the surface of water so that it spreads into a film. Calculate the thickness of the film. This experiment involves a treatment of estimations and inaccuracies introduced through the estimations. A mathematical approximation is to calculate the drop volume assuming it is a cube and the thickness by assuming the film is rectangular. The inaccuracies introduced by this should be discussed. Note that this experiment sets a maximum size for the diameter of a particle. The film may be several particles thick.

Mathematics: Calculation of volume of a sphere and volume of a cylinder. Handling approximations. Enquiry skills 7.1.3, 7.1.4

1 hour

Estimating the size of particles Cite evidence for the existence and size of particles.

Extension work for faster students Pursue the nature of particles further using models and distinguish between atoms and molecules. Confine the discussion to simple covalent compounds such as water.


Assessment


Draw diagrams illustrating the arrangement and movement of particles in a solid, a liquid and a gas.

Explain the following common observations in terms of particles.

a. Clothes drying on a line.

b. Salt crystals are all the same regular shape.

c. The formation of ice in the freezing compartment of a refrigerator;.

d. An inflated balloon slowly deflates over a few days.

e. The pressure in a car tyre is greater on a hot day than on a cold day.


The water in a tube is heated, as shown in the diagram. As the water is heated, the balloon increases in size. Explain why.

TIMSS, 1994–95, Grade 7–8

Imagine you are a water particle in the sea. One day you are near the surface and you get so hot in the sun that you have enough energy to escape from the sea into the air. Write about the adventures you have before you once again find yourself in the sea.

Predicting the outcome of experiments involving particles, as described in the possible teaching and learning activities, can also provide useful assessment opportunities.

Unit 7M.1



Mixtures, compounds and elements

About this unit This is the second of four units on materials for Grade 7. This unit builds on work in Units 6M.1 ‘Solutions’ and 6M.2 ‘Mixtures’. It introduces the concepts of elements and compounds, which in turn lead to a treatment of atomic theory in Unit 8M.1 ‘Particles’.

The unit is designed to guide your planning and teaching of lessons on materials. It provides a link between the standards for science and your lesson plans.



Introduce the unit to students by summarising what they will learn and how this will build on earlier work. Review the unit at the end, drawing out the main learning points, links to other work and 'real life' applications.

Previous learning To meet the expectations of this unit, students should already be able to separate insoluble solids from a liquid by filtration, purify a soluble solid by crystallisation, and distinguish between physical and chemical changes.

Expectations By the end of the unit, students are familiar with common physical methods for purifying substances. They understand that compounds are pure substances and that pure substances are characterised by sharp melting and boiling points. They know that elements are the building blocks from which compounds are made and name some common elements and compounds made from them. They show that the properties of compounds are very different from the properties of the elements from which they are made.

Students who progress further use chromatography as an analytical tool. They recognise that the gases of the air can be separated by fractionation of liquid air and understand how crystallisation can be used as an effective way of purifying chemicals. They explain the process of sublimation and give examples. Knowing the name of a simple compound they list the elements in it. They distinguish between atoms and molecules.

Resources The main resources needed for this unit are: • a variety of coloured pens or inks • electronic temperature sensor and datalogger • Hofmann voltameter

Key vocabulary and technical terms Students should understand, use and spell correctly: • separation, filtration, evaporation, distillation, fractionation,

chromatography, crystallisation, crystals, residue • melting, boiling, sublimation • mixture, compound, element • criterion of purity • names of a number of common elements and compounds • electrolysis, decomposition, combination, reaction

UNIT 7M.2 10 hours





6.11.4 Separate insoluble solids from a liquid by filtration and state everyday examples of filtration, such as coffee making, sewage works and water purification.

7.12.1 Explain how the processes of solution, filtration, evaporation and distillation can be used to make pure substances from mixtures and cite common examples of the use of each.

7.12.2 Perform chromatographic separations and explain why chromatography is widely used as a method for analysing mixtures.

7.12.3 Explain qualitatively the mechanism of chromatography

7.12.4 Know that fractional distillation is used widely in the oil industry for separating liquids of different boiling points, and explain how fractional distillation works.

6.11.5 Use crystallisation to obtain pure samples of a solute from a solution.

7.12.5 Know that most pure substances are characterised by sharp melting and boiling points and that they are either compounds or elements.

7.12.6 Use electrolysis to separate compounds into their elements. 7.12.7 Know that all matter is made from a small number of elements and that

they can be classified as solids, liquids or gases, metals or non-metals. 8.12.1 Know that the smallest particle of an

element is an atom and that atoms of one element are of one kind and are different from atoms of every other element.

7.12.8 Know that elements combine to form compounds and that the properties of compounds are different from the properties of their constituent elements.

6 hours

Making substances pure

4 hours

Compounds and elements

6.12.1 Distinguish between reversible and irreversible changes and know that reversible ones are physical and irreversible ones involve chemical changes in which new substances are formed.

7.12.9 Know that compounds can react chemically with each other to form new compounds.

8.12.1 Know that elements join together chemically to form compounds, that the smallest particle of a compound is a molecule, and that all molecules of a compound are made up of the same fixed number of atoms of the constituent elements.

Unit 7M.2


Activities


Recall earlier work on purifying mixtures Recall common mixtures that students will have met, including foodstuffs, cosmetics, solutions such as seawater and soil. Find out what students understand by the word mixture, perhaps by asking them to draw pictures of the particles in a mixture.

Find out also what they understand by the word pure. Show samples of foodstuffs that are advertised as ‘pure’ (e.g. bottled water). Discuss the difference between the use of the word in this context and the use of the word meaning ‘not a mixture’. Show that the ‘pure’ water is a mixture by discussing the ingredients list on the label.

Ask students for suggestions about how to make a pure substance from a mixture; remind them of the work on filtration done in Grade 6. Practical activities such as the evaporation of seawater or the separation of salt and sand can be done if they were not done in Grade 6.


Chromatography Demonstrate or describe the process of paper chromatography Split the class into groups and ask them to use this technique to investigate, following instructions, the composition of coloured inks. Ask students to suggest why some inks were pulled further up the paper than others by the rising water.

Take this further by providing information (from the Internet) on the use of chromatography as an analytical technique in medicine or forensic science. (Turn the forensic use into a problem to solve by asking students what forensic scientists could do if they found an ink stain at the scene of a crime.)

Ask more advanced students to separate the two forms of chlorophyll (A and B) from a concentrated alcoholic extract of plant leaves using alcohol as the eluent. The mechanism of chromatography can also be discussed with advanced students.

Use a selection of pens, some of which have pure single dyes and others two or three component mixtures. Black Quink™ fountain pen ink is a good one as it contains blue and yellow dyes, which cause some surprise. If the pen inks are permanent, use methylated spirit as the eluent.

Enquiry skill 7.4.1

Distillation and fractionation Recall from Grades 5 and 6 that a pure liquid can be obtained by condensing its vapour. The recovery of pure water from dirty water could be done as a practical exercise by students and the Liebig condenser demonstrated as an efficient way of cooling the water. Arrange a visit (or recall an earlier visit) to a water distillation plant to see the industrial application of this.

Visit opportunity: Water distillation plant.

6 hours

Making substances pure Explain how the processes of solution, filtration, evaporation and distillation can be used to make pure substances from mixtures and cite common examples of the use of each.

Perform chromatographic separations and explain why chromatography is widely used as a method for analysing mixtures.

Know that fractional distillation is used widely in the oil industry for separating liquids of different boiling points, and explain how fractional distillation works.

Know that most pure substances are characterised by sharp melting and boiling points and that they are either compounds or elements.

Recall earlier work on mixtures of liquids, noting that some are miscible while others are not. Ask the class to suggest ways of separating two liquids by distillation with the lower boiling liquid distilling first. Show, by separating a mixture of methylated spirits and water, that this is a difficult process because the alcohol will always be contaminated by water that has evaporated below its boiling point. Show, or discuss, how the separation can be improved by a second distillation.

Safety: Fire risk. The alcohol–water mixture must be heated on a water bath. If oil distillation is demonstrated, have a fire extinguisher close at hand and do not allow students near the equipment.

Unit 7M.2



Lead the discussion on to the concept of fractional distillation (fractionation) as a series of small distillations and condensations in a fractionating column leading to more efficient separation of liquid mixtures. Demonstrate the fractionation of crude oil (petroleum) and the physical properties and ease of combustion of the fractions. Show, with photographs and diagrams, how in a real situation the fractionation is a continuous process, with different fractions being tapped off at different points on the fractionating column. This and the fractionation of liquid air (see below) can be reinforced by an industrial visit.

Visit opportunity: Visit a refinery to find out about the fractionation of petroleum and liquid air.

Take the idea further with more able students by discussing the fractionation of liquid air. Ask students to create a flow chart of the whole process. Tell them to indicate on the flow chart the order in which the common gases are collected up the fractionating column (boiling points below zero can lead to conceptual difficulties here).

Enquiry skill 7.3.3

Sharp melting and boiling points as criteria of purity Ask students, in groups, to plot cooling curves of distilled water and seawater cooled down by an ice–salt mixture. Help students interpret the curves. Lead the discussion into sharp melting/freezing points as a criterion of purity. Recall the work on the boiling point of alcohol–water mixtures.

Establish, through discussion, that freezing and melting are opposites and that for a pure compound, they occur at the same sharp temperature. Ask students to list the melting points of some common substances on a scale that includes negative Celsius temperatures; make sure the melting points of nitrogen and oxygen appear on the scale.

Demonstrate that salt water boils at a higher temperature than pure water and over a range of temperatures, not at one sharp boiling point. List some boiling points of common liquids on a scale.

Recall (or repeat) work on crystallisation carried out in Grade 6. Recall the observation that all crystals of a pure substance were the same shape. Discuss the use of the process of crystallisation as a way of purifying a substance. Show and discuss pictures of industrial crystallisation of salt and sugar. Clarify, by questioning, what happens to any impurities during the crystallisation process. Show students a sample of cane syrup – the residue from making sugar from sugar cane.

ICT opportunity: An electronic temperature sensor and datalogger can be used to take the readings.

Enquiry skills 7.1.1, 7.3.3, 7.4.4

Demonstrating the properties of solid carbon dioxide (dry ice) and liquid nitrogen can add extra interest to the discussion on melting and freezing, but care should be taken over the proper transport of both and over the risk of cold burns.

Sublimation Introduce the concept of sublimation – the transition from gas to solid without the intermediate liquid phase – as an extension for more able students. Discuss examples such as the ice in a freezing compartment of a fridge. If solid carbon dioxide is available demonstrate that it vapourises without passing through the liquid phase. The sublimation temperature of pure carbon dioxide can be shown to be sharp at –78 °C.

A liquid-in-glass thermometer is unsuitable for measuring the sublimation temperature of carbon dioxide. A suitable electronic sensor should be used.

Safety: Care should be taken over the proper transport of solid carbon dioxide and over the risk of cold burns.



Electrolysis of water Divide the class into small groups and allow students to experience the electrolysis of water (made conductive by a small amount of sulfuric acid) using copper electrodes in small cells. They will see the gas collected and may be able to test for hydrogen and, possibly, oxygen. Repeat as a demonstration on a larger scale, using a Hofmann voltameter or similar and platinum electrodes, so that the gases can be collected in test-tubes and tested. Show that when hydrogen burns, condensation is formed. (The cobalt chloride paper test for water can be used.)

Establish through discussion that the passage of the current split the water through an irreversible chemical change into the simpler substances that bore no similarity to the original water. Discuss the reverse reaction when hydrogen burned. Illustrate the reaction with word equations. Introduce the idea of elements and compounds.

Safety: Only small quantities of hydrogen should be ignited by students under supervision

Making iron sulfide Ask students, in groups, to make iron sulfide in a test-tube by heating a mixture of iron filings and powdered sulfur. Tell them to test small samples of the starting materials and product with a magnet and with dilute acid to show a permanent chemical change. Tell them to discuss the evidence that a compound has been formed and to illustrate the reaction with a word equation.

During the reaction, draw the attention of the class to the red glow that spreads through the mixture, even after initial heating has been stopped, indicating that heat is evolved. Discuss this as evidence of a reaction.

Demonstrate the reaction of more reactive metals, such as zinc powder and magnesium powder with sulfur.

Use powdered roll sulfur (sublimed sulfur does not work). The iron may need degreasing with methylated sprits or similar beforehand.

Safety: Hydrogen sulfide is a poisonous gas; reactions that produce it should be carried out in a fume cupboard or outside. The reactions of zinc powder and magnesium powder with sulfur are vigorous and should not be done by students.

4 hours

Compounds and elements Know that all matter is made from a small number of elements and that they can be classified as solids, liquids or gases, metals or non-metals.

Use electrolysis to separate compounds into their elements.

Know that elements combine to form compounds and that the properties of compounds are different from the properties of their constituent elements.

Know that compounds can react chemically with each other to form new compounds.

Naming of elements and compounds Discuss the naming of some common simple compounds and show how the name can often give an indication of the elements that the compound contains. Compare the chemical and physical properties of some common compounds with those of the elements that make up the compound. Summarise the discussion in a table. Compounds to discuss: water, carbon dioxide, hydrogen sulfide, sodium chloride, iron oxide (or rust as a mixture of oxides), silicon dioxide.

Ask more advanced students to consider the elemental composition of salts such as sulfates, nitrates and carbonates.

Summary Ask students to construct a concept map that shows key differences between elements, compounds and mixtures. Give appropriate help, such as a number of key words to integrate into their map (e.g. element, mixture, compound, combine, separate). Use their maps to build a class concept map on the display board.

As a summary practical exercise, provide students with unknown substances and challenge them to determine whether they are mixtures, compounds or elements. Suitable substances include: salt/sugar mixture, copper carbonate, zinc powder, instant coffee.

Introduce more advanced students to the concepts of atoms and molecules at this stage (see Unit 8M.1).



Assessment


Farida opened a tin of white paint. The paint consisted of a liquid and particles of titanium dioxide that are insoluble in the liquid. The paint had separated into two layers, as shown in the diagram.

a. Is the paint an element, a compound or a mixture?

b. Is titanium dioxide an element, a compound or a mixture?

c. Why did the particles of titanium dioxide sink to the bottom?

d Farida stirred the paint and used it to paint a window frame. She got some of the paint on the glass. She could not get the paint off the glass with water. When she used a different liquid called white spirit the paint came off. Why could she remove the paint with white spirit but not with water?

QCA Key Stage 3 science, 2004, level 5

A student used chromatography to show which dyes are present in different coloured inks. The diagram shows some of her results. The results for purple ink are missing.

a. Give the colour of an ink which contains only one dye.

b. Give the colour of an ink which contains three dyes.

c. The purple ink is a mixture of the red and blue inks. On the diagram, draw the results you would expect from purple ink.

d What would be the colour of the spot labelled S?


Assessment

Set up activities that allow students to demonstrate what they have learned in this unit. The activities can be provided informally or formally during and at the end of the unit, or for homework. They can be selected from the teaching activities or can be new experiences. Choose tasks and questions from the examples to incorporate in the activities.

Provide each group of students with samples of substances such as iron filings, salt solution, copper carbonate powder, magnesium oxide, etc., and challenge them to devise a number of simple investigations to find out whether the substances are likely to be elements, compounds or mixtures.

This activity will be much more effective if it is carried out after Unit 7M.4 on acidity has been taught.

Enquiry skill 7.1.1

Unit 7M.2

particles of insoluble titanium dioxide

liquid



The diagram shows a liquid being distilled using a fractionating column. Answer the following questions, giving explanations for your answers.

a. Which part of the column is hotter, A or B?

b. If the column is used to distil a mixture of ethanol (b.pt 78 °C) and water (b.pt 100 °C), which of the two liquids will be present in the first tube to fill.

c. What kinds of changes of state are happening:

i. in the round bottomed flask;

ii. in the fractionating column;

iii. in the condenser?

d. Fractionation can be used to separate oxygen (b.pt –183 °C) and nitrogen (b.pt –196 °C) from liquid air. Which gas will distil from the column first?

e. Name another industrial application of fractional distillation.



Combustion

About this unit This unit is the third of four units on materials for Grade 7.

The unit is designed to guide your planning and teaching of lessons on materials . It provides a link between the standards for science and your lesson plans.




Previous learning To meet the expectations of this unit, students should already have studied combustion as a permanent change and be aware of the role of air in combustion and how deprivation of air can halt combustion.

Expectations By the end of the unit, students know the composition of the air and the properties of its main constituents, and understand the principles of combustion.

Students who progress further know that when substances burn in air, compounds called oxides are formed. They realise that reactions such as rusting and tarnishing are chemically the same as burning. They know that nitrogen is inert and does not support combustion. They know that hydrocarbons burn to form carbon dioxide and water.

Resources The main resources needed for this unit are: • oxygen cylinder • gas syringes and silica tube, bell jar

Key vocabulary and technical terms Students should understand, use and spell correctly: • combustion, rusting, tarnishing • air, nitrogen, oxygen, carbon dioxide, argon • oxide • inert

UNIT 7M.3 7 hours





7.13.1 Know that air consists of one-fifth oxygen, four-fifths nitrogen, small quantities of other gases, principally argon and carbon dioxide, and a variable proportion of water.

7.13.2 Demonstrate that part of the air is used up by burning.

6.12.3 Know that heating can bring about temporary, physical, changes in some materials and permanent, chemical, changes in others. Distinguish between heating and burning.

7.13.3 Know that when a substance burns, it combines chemically with the oxygen in the air and that the overall mass of the product(s) is greater than the original mass of the material.

8.12.2 Know that elements join together chemically to form compounds, that the smallest particle of a compound is a molecule, and that all molecules of a compound are made up of the same fixed number of atoms of the constituent elements.

5 hours

Air and burning

2 hours

Properties of oxygen and nitrogen

7.13.4 Know the common properties of oxygen and nitrogen, such as the reactivity of oxygen towards both metals and non-metals forming oxides and the relative chemical unreactivity of nitrogen.

7.13.5 Use word equations to describe the reactions when elements burn.

Unit 7M.3


Activities


Looking at a flame In Grade 6, students should have repeated the Faraday’s classic 1860s study of what happens when a candle burns. Ask them to recall some of their observations about the structure of the flame and what was happening in different parts of it.

Demonstrate the use of a Bunsen burner and give students an opportunity to learn, through practice, how to light it and use it safely, what the different parts are for, and what happens in the different parts of the flame.

Demonstrate that the blue cone in the roaring flame is unburnt gas by lighting the burner when its air hole is open after placing a match head suspended by a pin, in the area of the unburnt gas.

Discuss the difference between the roaring flame and the yellow flame and the cause of the yellowness.

Enquiry skill 7.4.4


Burning candles under jars This is a repeat of a short activity done in Grade six and serves as a reminder and an introduction to this section. Give out three small candles and three different-sized jam jars to each group. Ask them to light the three candles and then invert the jars over the top of each simultaneously and find out how long it took for each candle to go out.

Ask the class for ideas why the candles went out and why the one under the largest jar took longest to go out. They will probably suggest that it is because the candle ‘used up the air’. Point out that the air did not appear to be ‘used up’ completely as there was still air in the jars. Tell them that the next demonstration will try and answer this question

Candle in a bell jar Light a candle floating in an evaporating basin in a trough of water. Place a bell jar with the stopper removed over the top of it. Replace the stopper. Ensure there is a space at the bottom of the jar for water to enter it. Watch carefully what happens to the candle and the water level. The water level rises about one fifth of the way up inside the jar, indicating that about one-fifth of the air has been ‘used up’ during the burning.

There is much discussion of this experiment in the literature. It seems fairly certain that reason for the rise is not that the oxygen, one-fifth of the air, has been used up. Nevertheless, this is still a possible and logical explanation, even if probably untrue. Make up your own mind how you treat the explanation of this observation.

5 hours

Air and burning Know that air consists of one-fifth oxygen, four-fifths nitrogen, small quantities of other gases, principally argon and carbon dioxide, and a variable proportion of water.

Demonstrate that part of the air is used up by burning.

Know that when a substance burns, it combines chemically with the oxygen in the air and that the overall mass of the product(s) is greater than the original mass of the material.

Rusting Set up a similar activity using steel wool. Degrease a small piece of steel wool by shaking it in methylated spirits and then wet it with water. Place it in an inverted 100 cm3 graduated tube or inverted burette so that it is stuck near the top. Place the inverted tube in a trough or large beaker of water and equalise the levels inside and out (preferably at zero on the graduations). Leave for a week and ask the class to make daily observations of the steel wool and water level in the tube over a week. They should note, and link, two observations: the steel wool rusts and the water rises. The maximum rise will be 20% of the tube.

Students should also note the parallel between this activity and the previous one. Part of the air is used and that part occupies about one-fifth by volume.

Unit 7M.3



Demonstration of absorption of oxygen This is a third demonstration that leads to a similar conclusion. This one is more accurate than the other two and can be linked to the need for accuracy in observations. Set up two gas syringes so that 100 cm3 of air can be passed back and forth over some strongly heated copper powder in a silica tube. It will be evident that the volume of the air diminishes gradually in the process to something above 80 cm3 and then remains constant. Stop the heating and allow the equipment to cool and the gas to contract. It will contract down to a little below 80 cm3.

Empty the silica tube and show students what has happened to the copper. Show some copper oxide in a bottle and note the possible similarity between the black residue and the copper oxide.

Enquiry skill 7.1.4

Composition of air Discuss the three demonstrations with the class. Ask for explanations. It is clear that air must be a mixture of gases and that one of these is involved in all three reactions – the burning of wax, the rusting of iron and the tarnishing of copper. Introduce the class to the composition of air and discuss briefly the nature of the gases. They will meet carbon dioxide in Unit 7M.4 and they will investigate nitrogen further in this unit. Give the main characteristics of the other common constituents, particularly argon.

Give the class a list of the main constituents of dry air and their proportions and ask them first to copy the table into their books and then (at home) to display the information as a pie chart. Discuss briefly when it is appropriate to use a pie chart as a way of communicating information visually. Students with ICT knowledge might like to do this using spreadsheet software, such as Microsoft Excel.

ICT opportunity: Use of spreadsheet software.

Enquiry skill 7.3.3

Burning magnesium in a crucible Ask the class whether, when something burns, the product has a greater or smaller mass than the material that is burnt. Most will probably agree with the eighteenth-century chemists like Priestley that there is a loss in mass (see the next section) when something burns. This demonstration shows that there is an increase in mass when magnesium burns.

First demonstrate what happens when magnesium burns. Show that a white powder is formed that is very light in weight. Let students handle the powder. Ask them whether they think that the mass of the powder is greater or less than the mass of the original magnesium.

Clean and weigh a crucible with its lid. Place in it a cleaned 10 cm strip of magnesium ribbon coiled so that there is good contact with the side of the crucible. Weigh it again. Set it up on a pipe clay triangle and heat it very strongly. While it is heating, carefully raise the lid now and then to let in more air but try not to allow any oxide to escape. Continue until it is all burnt. Allow it to cool and reweigh.

The crucible will have increased in mass. Subtraction will give the amount by which the mass has increased from that of the original magnesium. It is possible to show that the mass increases by a ratio of 3 to 5 as predicted from stoichiometric considerations, but few students will have reached this level of understanding.

The key point to note from this demonstration is that there was a marked increase in mass when magnesium burned, which suggests it had combined with something – the oxygen – in the air. Lead to a definition of burning.



What was phlogiston? The phlogiston theory is an excellent example of the very logical theory that was the basis of chemical theory until a little before 1800. More advanced students can find out about it from books and the Internet and can study it as an example of how scientific theories are overthrown by refutation. It explained almost all observations made about the chemical changes that took place during burning and metal refining. A fundamental prediction of the theory was, however, the when things burn they release phlogiston into the air and so lose mass. The theory collapsed when it was shown that when things burn there is an increase in mass. The brilliant chemist Count Antoine LaVoisier was a leading opponent of the phlogiston theory. He was executed in the French Revolution (not for overturning the phlogiston theory but for being a Count).

Challenge students to explain the results from the experiment that involved burning candles under three different-sized jam jars earlier in this unit in terms of the phlogiston theory.


2 hours

Properties of oxygen and nitrogen Know the common properties of oxygen and nitrogen, such as the reactivity of oxygen towards both metals and non-metals forming oxides and the relative chemical unreactivity of nitrogen.

Burning substances in air and in oxygen This work can either be done as a series of demonstrations or as group work, although it is difficult to do as group work unless the school has an oxygen cylinder. If there is no oxygen cylinder, prepare the gas by heating oxygen mixture or by the catalytic decomposition of 20 volume hydrogen peroxide.

Ask students to predict what might be the effect of burning substances in oxygen compared with burning them in air. Carry out the activity to test their predictions. It is advisable to do the tests in such a manner that the more spectacular ones are left until the last.

Students can do the work in boiling tubes, which they fill in advance at the cylinder and stopper. Teacher demonstrations should be done in gas jars.

Students may burn substances such as wood, steel wool and charcoal. Make sure they include the test for oxygen: the relighting of a glowing wooden spill. The following should only be burnt in oxygen as a teacher demonstration: sulfur, magnesium, a candle.

In all cases, students should notice the difference between burning the substance in air and in pure oxygen.

The candle is an example of a hydrocarbon. Discuss with the class the meaning of the word hydrocarbon. Ask them if they can give any other examples of hydrocarbons. They will probably be able to suggest things like petrol and natural gas. Ask them to predict what the products of burning a hydrocarbon are (remind them of the study of the candle flame in Grade 6). Ensure that they realise that the carbon will form carbon dioxide and the hydrogen will form water (hydrogen oxide). Remind them that incomplete burning of hydrocarbons can also form carbon (soot) and it is this that gives a candle its yellow flame.

Spend some time at the end of the session writing word equations for all the reactions.

If the unit on acidity has already been done, the pH of the solution of the products of burning can be measured to show the difference between the oxides of metals and non-metals.

Enquiry skill 7.4.4

Safety: Gas cylinders must be used with all appropriate safety precautions. The cylinder must be secured vertically and two reduction valves employed, one operable only with a key. 20 volume hydrogen peroxide burns the skin and should only be handled by the teacher. Students should not look directly at burning magnesium. Take care when burning sulfur and use a fume cupboard.



Reactions of nitrogen Nitrogen is not an easy gas to prepare but is available in cylinders. If it is available at your school, repeat the demonstrations done with oxygen to show that, with one exception, the gas extinguishes anything that is burning.

The exception is magnesium. If a well-burning magnesium ribbon is lowered slowly into a jar of nitrogen, it will continue to burn with a smoky flame, forming magnesium nitride. Write a word equation for the reaction on the board or OHP. Stress that this is a very rare exception and that very few substances will burn in nitrogen.

Draw the conclusion that nitrogen is a very unreactive gas.

Uses of the gases of the air Ask students to construct a flow chart showing air at the centre, with its constituent gases around it and arrows to show some of the best-known uses for the gases.

Separating the gases of the air We can buy oxygen to use in laboratories and hospitals quite cheaply and easily. Ask students to find out how it is made from air.

It is made by first liquefying air by a series of cooling processes and then fractionating it – just like crude oil but requiring less heat. The gas with the lowest boiling point distils first, nitrogen at –196 °C, followed by oxygen at –183 °C.


Assessment


The diagrams show two Bunsen burners. One burner has the air hole closed, and the other has the air hole open.

a. Explain why opening the air hole of a Bunsen burner makes the flame hotter.

b. Natural gas is methane, CH4. It is burned in a Bunsen burner. Complete the word equation for the chemical reaction in the clear blue flame.

methane + ___________ → .___________ + ___________


The exhaust gases of a car with a petrol engine are analysed and the results are shown in the table.

a. What percentage of the air going into the engine was oxygen?

b. Explain why there is only 1% of oxygen in the exhaust gases coming out of the car engine.

c. Explain the origin of the 55% nitrogen in the exhaust gases.

d. Name one gas that comes under the heading ‘other gases’ and explain where it came from.

e. Petrol is a mixture of compounds that contains only carbon and hydrogen. Complete combustion of petrol produces carbon dioxide and one other substance. What is this other substance?

f. Sometimes smoke can be seen coming from a car exhaust. Name the substance that forms the main part of the smoke and explain why it is produced.

Gas % by volume

Carbon dioxide 17

Oxygen 1

Nitrogen 55

Other gases 27

What would you observe if you lowered a burning candle into jars of the following gases:

air oxygen nitrogen carbon dioxide.


If the mass of the Earth’s atmosphere is 5 thousand million million tonnes, how much argon is there in the atmosphere?

Unit 7M.3



Acidity

About this unit This unit is the fourth of four units on materials for Grade 7.

The unit is designed to guide your planning and teaching of lessons on physical processes. It provides a link between the standards for science and your lesson plans.




Previous learning To meet the expectations of this unit, students should already appreciate the nature of chemical reactions in which materials react together to form new products. They do not need any previous knowledge of acidity.

Expectations By the end of the unit, students name some common acids and alkalis and classify solutions as alkaline, acidic or neutral. They use indicators and understand the pH scale. They describe what happens to the pH of an acid when it is neutralised, display continuous change in pH graphically and give everyday examples of neutralisation. They know the reaction between acids and carbonates and the test for carbon dioxide and express reactions as word equations.

Students who progress further recognise that acids react with carbonates to give carbon dioxide and that they also react with metals.

Resources The main resources needed for this unit are: • litmus and pH paper booklets • vinegar, lemon juice, toothpaste, stomach powder • coloured plants (e.g. red cabbage, beetroot)

Key vocabulary and technical terms Students should understand, use and spell correctly: • acid, alkali, pH • litmus, universal indicator • carbonate, carbon dioxide, limewater • neutralisation

UNIT 7M.4 8 hours





7.14.2 Know that some acids and alkalis can be corrosive and hazardous, and be aware of the use of hazard symbols to describe this.

6.12.1 Distinguish between reversible and irreversible changes and know that reversible ones are physical and irreversible ones involve chemical changes in which new substances are formed.

7.14.1 List the widely known characteristics of common acids and alkalis, such as the sharp taste of acids and the soapy feel and bitter taste of alkalis.

8.13.3 Know that when metal reacts with air, oxygen or water, an oxide or hydroxide is formed and that if this is soluble in water, the solution is alkaline.

7.14.3 Know that litmus solution is an indicator that can be used to classify some common solutions as acidic or alkaline.

7.14.4 Know that many naturally occurring colours act as indicators.

7.14.5 Know that the pH scale is a measure of the acidity of an aqueous solution and that the pH of a solution can be determined by universal indicator colour changes.

7.14.6 Know where strong and weak acids, strong and weak alkalis, and pure water occur on the pH scale.

7.14.7 Know that acids and alkalis react with each other and that the process is called neutralisation.

8.14.1 Know the different reactions by which salts can be made.

7.14.8 Know that acids react with carbonates to liberate carbon dioxide, which can be identified by bubbling it through fresh limewater.

8,13.1 Deduce a reactivity series for common metals based on their reactions with air, oxygen, water and dilute acids.

4 hours

Acidity and pH

4 hours

Properties of acids and alkalis

7.14.8 Express chemical reactions in the form of word equations.

Unit 7M.4


Activities


What are acids? Ask students what the word acid means to them. A good way of doing it is to ask them to draw a concept map, first individually and then in groups. Transfer the significant features to one that you put on the board or OHP.

It is likely that someone will have made a link with fruit juice, perhaps lemon juice, and the sharp taste characteristic of fruits. Explain that this is an important property of acids (but also explain that many can be harmful if tasted).

Ask for examples of substances that students think are acids or contain acids. List them on the board or OHP. Some may suggest household chemicals, such as ammonia, that are not acidic. It is important for them to realise that there are many such fluids that are not acidic. Tell them that they will now spend a number of lessons finding out what acids are and what they do. Make a collection of many of the acids that students have mentioned. Add dilute hydrochloric and sulfuric acids to this list if they are not there. Explain that sulfuric acid is the main acid of the chemical industry and that Qatar is in the process of establishing sulfuric acid manufacturing using the sulfur that is an impurity in Qatar gas. Show them some Qatar sulfur.


Indicators Explain that taste is not a very good way of identifying acidic substances and that instead we use substances called indicators. Show students litmus and explain its origin. Show them litmus paper, explain what it is and show them how to use it. Provide each group with some samples of solutions; most of these should be acids but include water and a few alkalis (e.g. sodium bicarbonate solution). Also give them distilled water (tap water may suffice; test it first to ensure that it does not change the colour of either red or blue litmus paper) Ask them to test all with both red and blue litmus paper and tabulate the results. Tell them to list the solutions that are acidic.

Discuss the solutions that turn red litmus blue and introduce the name alkali for these.

4 hours

Acidity and pH List the widely known characteristics of common acids and alkalis, such as the sharp taste of acids and the soapy feel and bitter taste of alkalis.

Know that litmus solution is an indicator that can be used to classify some common solutions as acidic or alkaline.

Know that the pH scale is a measure of the acidity of an aqueous solution and that the pH of a solution can be determined by universal indicator colour changes.

Know where strong and weak acids, strong and weak alkalis, and pure water occur on the pH scale.

Home-made indicators Explain again the origins of litmus and challenge students, working in groups, to find out whether other natural colours are also sensitive to acids. Encourage them and help them to plan an investigation to find out the answer. Help groups with their plans by reminding them of techniques for extracting colour from plants – which they do when they make tea. Help them decide which plants they are going to investigate.

After they have extracted the colour, help them develop a standard test using an acid and an alkali (two acids and two alkalis are better, in each case recommend one strong and one weak but at this stage do not distinguish between them in these terms). Make sure they also note the colour in water.

Encourage them to prepare indicator paper for the tests using filter paper.

Most natural colours show pH related colour changes, even tea. Red cabbage makes a very good indicator with a sequence of pH-related colour changes yellow–green–purple–red. Beetroot gives a red–green change. Red hibiscus and red bougainvillea flowers are also satisfactory.

Enquiry skill 7.1.1

Unit 7M.4



Universal indicators The work with home-made indicators, particularly red cabbage, may have shown that there can be more than two colours involved in an indicator colour change. At this stage, introduce universal indicator paper, which can turn many shades with different solutions. Explain that it is made from a mixture of different plant extracts (in fact many of the components are now synthetic).

Repeat the earlier work with litmus but use universal indicator paper instead. Ask students to stick the paper in their tables next to the name of the substance tested. Finally, draw attention to the colour sequence on the indicator chart and tell them to write the number related to the colour in the chart in a new table column.

It is helpful to make class sets of the indicator charts using the booklet covers laminated to a small strip of cardboard. These can be kept for re-use.

The pH scale Explain that the numbers on the chart, which they now have in their tables, represent a scale of acidity. Not all acids (or alkalis) are the same: some are stronger than others. Draw the scale on the board or OHP, indicating the direction of increase in strength of acids and alkalis and the areas of the scale that represent strong and weak alkalis. It is important that students realise that this scale is a continuum with water in the middle. Tell them to make a copy of the scale in their books and illustrate it by showing litmus colours and universal indicator colours for each pH value.

Do not attempt to explain the origin of the numbers on the scale; just tell students that the numbers do have meaning but they will not study that until Grade 12.

Give out small pieces of pH paper and ask students to test the pH of some materials around the home (specifically include toothpaste).

Demonstrate the pH meter.

Teachers should be aware that colour-blind boys will experience some difficulties distinguishing between some of the shades of colour in the universal indicator scale

Introduction Refer to the common complaint of acid indigestion – the stomach ache that eating too many apples or similar fruits can cause. Remind students that there are many remedies – stomach powders – for this that can be bought at pharmacies and supermarkets.

Give each group a small quantity of an acid, such as vinegar, in a test-tube and ask them to add a small part of a stomach powder tablet. A reaction will be obvious.

Ask them to dissolve the stomach powder in water and test its pH. It will be alkaline.

4 hours

Properties of acids and alkalis Know that acids and alkalis react with each other and that the process is called neutralisation

Know that acids react with carbonates to liberate carbon dioxide, which can be identified by bubbling it through fresh limewater.

Express chemical reactions in the form of word equations.

Neutralisation reactions The stomach powder reaction can lead on to general series of reactions that you can introduce as neutralisation reactions. In these reactions, the acidity is neutralised and the pH raised to 7.

Give the groups some acid solution and some alkalis and ask them find out what happens when all combinations of an acid and an alkali are tried. Tell them to add the alkali to the acid and observe what happens and also check pH changes. Encourage them to use small quantities.

Tell them to write their observations in a 2-way table: acids on one axis and alkalis on the other.



Discuss the results. Sometimes, when the alkali is a carbonate, a reaction will be very obvious but in other instances it is not. Ask if anyone observed a temperature change. If they did not, ask them to redo the reaction between sodium hydroxide and hydrochloric acid.

Conclude that the reaction between acids and alkalis is a general one and is called neutralisation. Discuss the reaction and write a word equation for what they know about it – use the words ‘new compound(s)’ for anything that is unknown.

Carbon dioxide Show students the limewater test for carbon dioxide. A small-scale test is often best – a drop on a glass rod put into the gas. Ask them to test the gas given off in some of the reactions.

Help them construct a word equation for reactions that give off carbon dioxide.

Discuss the reaction with them and ensure that they know that, when carbon dioxide is produced, the compound that reacted with the acid was one of a class called carbonates. Give a few examples of carbonates and show that they all react with acid in the same way.

Limewater should always be made fresh just before the lesson.

Action with metals Encourage more advanced students to study the reaction between acids and some metals (e.g. magnesium, iron, zinc). This will be studied in detail in Grade 8.

A titration This activity shows in more detail what happens during a neutralisation. Use the reaction between vinegar (2 mol/dm3 ethanoic acid) and lime (calcium hydroxide). Perform the reaction yourself beforehand to determine the reacting quantities. Ideally, you should use about 25 cm3 of the vinegar in a 100 cm beaker and add the alkali in standard amounts of one small spatula full, such that five spatulas are sufficient to raise the pH to 7 and then beyond.

Give careful instructions to the class, showing them the size of the standard spatula full. Impress on them that each addition must be of the same amount of the solid alkali. They should take the pH of the suspension after each addition and stirring, and carry on for several additions after the pH has risen to neutral. Tell them to record the pH after each addition in a table of results.

Finally, they should display the results in a line graph with pH on the y-axis. Ask them to conclude, from the graph, the exact number of spatulas of lime that would just neutralise the vinegar.


Acids and the environment After a rain shower in winter, ask students to test the pH of rainwater. They will find that it is acid and not neutral like pure water. Ask the class to suggest reasons for this. Something must have dissolved in the water and made it acid. Explain that there are several gases in the air that do this. Carbon dioxide is one and sulfur dioxide is another. Explain that both are there naturally but that their concentration is increased by human activities, such as burning fuel in cars and in power stations.



Hazards of acids and alkalis Display a series of the common hazard symbols in the laboratory.

Refer back to the start of the topic. Almost certainly someone will have said that they think that acids are dangerous. Ask them whether they still think that acids are dangerous. Ask them whether they would worry about washing their hands in vinegar or lemon juice? The answer should be no. Then ask what happens if they get lemon juice in their eye? Conclude that our skin is resistant to acids but that that if acids get in a cut or in the eye then they hurt and can cause damage. Tell them that our stomachs contain a strong acid.

Warn students, however, that acid splashed can destroy clothing, which is why protective clothing is common in laboratories.

Warn them too that they should be careful with strong alkalis as they can destroy the skin. Tell them that strong alkali splashes should be washed off with a lot of water.

Explain that some concentrated acids may be very dangerous to the skin; this is not because they are acids but because they suck water from the skin causing ‘acid burns’. Not all acids do this – hydrochloric acid does not, for example.

Demonstrate the action of sulfuric acid on sugar (preferably in a fume cupboard). Pour some concentrated sulfuric acid onto about 1 cm depth of sugar in a 250 cm3 beaker. Let students watch how the acid slowly removes the elements of water from the sugar, leaving a charred lump of carbon. Point out that it will do much the same to human flesh.

Introduce and explain the meaning of the chemical hazard symbols.

Consolidation – return to the concept map Ask students to return to the concept map that they produced at the start of the unit. Tell them to modify it to incorporate what they have learnt in this unit. Look at what they write and note, and deal with, any misconceptions.


Assessment


The graph shows the change in pH as Ibrahim ate a meal. X marks the point where he started eating.

a. What was the pH in his mouth before he started eating?

b. Before he started chewing, was his mouth acidic, alkaline or neutral? Explain your answer.

c. After a few minutes chewing, was his mouth acidic, alkaline or neutral? Explain your answer

d. Bacteria that cause tooth decay survive best when the mouth is acid. Toothpaste neutralises this acidity. What kind of a chemical is in the toothpaste that does this. What will happen to the pH in Ibrahim’s mouth when he cleans his teeth with toothpaste?

The pH of a wasp sting is 10. The pH of an ant bite is 3.

a. What colour will litmus paper turn if you use it to test the fluid of a wasp sting and then an ant bite? Explain your answer.

b. Use the table showing the pH of common household chemicals to decide what is the best chemical to put on each of these stings. Explain your answer.

Solution pH

Lemon juice 3

Vinegar 4

Water 7

Bicarbonate of soda solution

9

Washing soda solution

11


A scientist wanted to compare four gases to see which gas might make rainwater acidic. She collected the same volume of each gas and bubbled each of them through the same amount of water. She tested each sample with a pH meter and found that they all had a pH of less than 7. She then added drops of an alkali to each until the pH meter showed that the pH was exactly 7. She also tested air in the same way. The results are shown in the table.

a. Which gas made the water most acidic?

b. Why did she use the same volume of each gas?

c. Which gas had the least effect on the acidity?

d. Why was it important that she tested air?

e. What effect did the alkali have on the acid?

Gas Number of drops of alkali used

Vehicle exhaust 62

Human breath 18

Gas from a sparkling drink

75

Air 5

Unit 7M.4

111 | Qatar science scheme of work | Grade 7 | Unit 7E.1 | Earth and space 1 © Education Institute 2005

GRADE 7: Earth and space 1

Origins and properties of rocks

About this unit This unit is the only unit on Earth and space for Grade 7.

The unit is designed to guide your planning and teaching of lessons on Earth and space. It provides a link between the standards for science and your lesson plans




Previous learning To meet the expectations of this unit, students should already be aware that there are rocks beneath all the surfaces of the Earth and that these have a variety of different properties and that weathering of these rocks provides the matrix from which soil is made.

Expectations By the end of the unit, students describe different rocks in terms of texture, porosity and density. They know the typical features and the origins of sedimentary, metamorphic and igneous rocks. They understand the main features of geological time. They know the internal structure of the Earth.

Students who progress further explain geological processes and events such as volcanoes and earthquakes in terms of plate tectonics.

Resources The main resources needed for this unit are: • collection of igneous, metamorphic and sedimentary rocks • top-pan balance • newsprint – at least 15 m • poster showing an erupting volcano • Internet access

Key vocabulary and technical terms Students should understand, use and spell correctly: • rock, mineral • igneous, metamorphic, sedimentary, rock cycle • fragmented, foliated, crystalline textures • volcano, earthquake, lava, intrusions • fossils, geological timescale, eons, eras • continental drift, plates, plate tectonics

UNIT 7E.1 10 hours





7.15.1 Recognise properties of rocks, such as texture, porosity and density.

7.15.2 Describe how igneous rocks crystallise from magma released during movements of the surface of the Earth, and relate crystal size to cooling rate.

5.11.1 Compare different rocks and group them according to readily observable characteristics; devise tests for making simple comparisons between different rock types, such as the effect of rubbing and porosity.

7.15.3 Use the distinctive features of igneous, sedimentary and metamorphic rocks to distinguish between them.

7.15.4 Describe how sedimentary rocks are formed from sediment under the influence of pressure.

5.11.3 Know that there is rock under all the Earth’s surfaces and that soil is formed from rocks by the processes of weathering.

7.15.5 Know that metamorphic rocks are formed from sedimentary rocks that are subjected to high pressure and/or temperature.

7.15.6 Know that rocks are made up of pure compounds called minerals, many of which are important raw materials for industry.

10A.18.7 Describe, with essential chemical reactions, the extraction of steel from iron ore and recycled scrap iron in the electric arc furnace.

10A.18.10 Be aware that large-scale extraction and refining processes are often damaging to the environment and that this has to be balanced against the benefits of the processes; list some of the steps taken to minimise environmental degradation in the processes studied.

7.15.7 Describe the formation of oil and gas and how they are now extracted and used.

10A.18.3 Know how a variety of fuels and other useful compounds can be obtained from petroleum and natural gas

9.16.4 Name the common fossil fuels and explain their origin.

7.15.8 Know that Earth’s history can be conveniently divided into periods categorised by particular geological and climatic conditions and by the nature of the things that were living during the periods.

7.15.10 Know that the surface of the Earth consists of moving continental plates floating on a layer of molten rock below the surface.

4 hours

The rock cycle

2 hours

Useful materials from rocks

4 hours

Geological history and plate tectonics

7.15.9 Know the main features of the internal structure of the Earth. 7.15.11 Show how the theory of plate tectonics can explain the main mountain ranges and volcano and earthquake zones.

7.2.2 Know that science is divided into many different fields of study and realise that although scientists working in these fields may use very different techniques, they share a common methodology.

Unit 7E.1


Activities


Introduction to geology As an introduction to this unit, spend a short time explaining how science is conveniently divided up into different fields of study. Describe some of the main ones and ask students if they know the names of them. Include chemistry, physics, astronomy and biology. Introduce the study of geology as the study of the structure of the Earth, and particularly the study of the rocks that make up the Earth’s crust. Ensure that the students realise that although all these disciplines have different names, they all have a common methodology.

Enquiry skill 7.2.2


Properties of rocks – appearance For this unit, you will need a collection of common rocks of all three types. These should be named but, at the start of this topic, they should not be classified according to type.

Hand out rock samples to students, working in groups. Ensure that each group has at least one example of a sedimentary, metamorphic and igneous rock. Give out hand lenses and ask the groups to look at the fine structure and the feel of each and to try to group them. They should be able to distinguish the three types, which you can then name. At this stage do not discuss their different origins.

Now get groups to develop a table of the properties of the rock samples as described below.

Enquiry skill 7.4.1

Properties of rocks – permeability Ask groups to weigh a rock sample, immerse it in water for a few minutes and then take it out and mop it dry. Then ask them to reweigh it to see whether water has been absorbed.

Properties of rocks – density Ask groups to find the volume of the weighed rock by displacement of water in a measuring cylinder. Then ask them to calculate its density

4 hours

The rock cycle Recognise properties of rocks, such as texture, porosity and density.

Describe how igneous rocks crystallise from magma released during movements of the surface of the Earth, and relate crystal size to cooling rate.

Use the distinctive features of igneous, sedimentary and metamorphic rocks to distinguish between them.

Describe how sedimentary rocks are formed from sediment under the influence of pressure.

Know that metamorphic rocks are formed from sedimentary rocks that are subjected to high pressure and/or temperature.

Know that science is divided into many different fields of study and realise that although scientists working in these fields may use very different techniques, they share a common methodology.

Properties of rocks – hardness Ask groups to sort the rocks in order of harness by finding out which rock will mark which. This is the basis of Mohs’ scale, which students can be given.

Only do this activity if there are many specimens of a rock sample, as it damages the specimen.

Unit 7E.1



Igneous, metamorphic and sedimentary rocks and the structure of the Earth

Set students a library and Internet task to research the origins of these three classes of rocks, find out about their chief characteristics and discover how they are related. As a result of their research, they should be able to name common examples of each type. Research work into igneous rocks will also lead to a knowledge of the structure of the Earth and the significance of the rate of cooling of molten magma in the rock cycle. They will also discover mechanisms through which igneous rocks reach the surface.

As students carry out this research, they should have available the table of results of their activities on the properties of rocks – they need to ensure that they can identify clearly which class each sample belongs to.

Summarise their findings in a class discussion and note the main properties of each type of rock on the board or OHP. Introduce the rock cycle to show how the three types are inter-dependent. Trace some common rocks round the cycle to show the origins of sedimentary rocks (e.g. limestone, sandstone, rock salt) and the relationships (e.g. between limestone and marble, sandstone and quartz).

Explain the appearance of rocks in terms of their origins and, where possible, show examples of each. Discuss how crystalline, fragmented and foliated textures arise. Recall work done on growing crystals in Grade 6 – in particular that, if crystals grow slowly, they tend to be larger than if they grow fast. Use this to explain the difference in crystal size in igneous rocks that cool down fast (as in lava flows from volcanoes) and those that cool down slowly (such as in intrusions), and also explain why those that cool under water often form glasses with no crystalline structure.


Enquiry skill 7.1.2

Animations of the rock cycle Animations of the rock cycle can be found on the Internet. These can be accessed by the students or by you to be used in class. These show very clearly how sedimentary rocks are formed through erosion of other rocks; how these can be changed into metamorphic rocks and how all rocks can be sucked down into the magma to be recycled as intrusions or during volcanic activity.

ICT opportunity: Use of animations from the Internet. A very good example of a rock cycle animation can be found on the Houghton Mifflin education textbook support website at www.classzone.com/books/earth_science/ terc/navigation/visualization.cfm. Enter the keycode ES0602.

Note that some animations can be downloaded while others must be viewed on their sites and downloading enfringes copyright. An Internet connection to the classroom is essential if these are to be used.



Minerals Refer back to the initial examination of rock samples and the discussion on rock textures. Draw the attention of the class to what they observed when they looked at igneous rocks. Alternatively, hand out samples of igneous rocks and ask students, in groups, to re-examine them and report what they see.

They should report that they see small regular-shaped crystals. Ask them what they recall about crystals from their work on crystals in Grade 6 and earlier in Grade 7. The important point to bring out is that crystals are pure compounds and that igneous rocks can be seen to be mixtures of different crystals, or mixtures of compounds, called minerals.

Some of these minerals are of use to us because useful materials such as metals can be extracted from them. Ask the class to find out, from their textbooks, the library or the Internet, something about the importance of the following minerals and where they are mined: limestone, haematite, bauxite, copper pyrites, zinc blende (any others you may wish to add).


Enquiry skill 7.1.2

2 hours

Useful materials from rocks Know that rocks are made up of pure compounds called minerals, many of which are important raw materials for industry.

Describe the formation of oil and gas and how they are now extracted and used.

Petroleum and natural gas Ask the class to use their textbooks, the library or the Internet to find out about the process by which oil and natural gas were formed, how long ago this happened, and how it is that there are deposits of these minerals in certain places throughout the world now.

Either ask students to do small individual study projects on how these minerals were formed or let them work in groups to create a class display on the topic. The main focus should be on the Qatar gas field, its origins, how the gas is extracted and its importance to the country. This work will be followed up in more detail in Grade 9.


Enquiry skill 7.1.2

4 hours

Geological history and plate tectonics Know that Earth’s history can be conveniently divided into periods categorised by particular geological and climatic conditions and by the nature of the things that were living during the periods.

Know the main features of the internal structure of the Earth.

Was Qatar always as it is now? Ask students whether they think Qatar was always as it is now. Could it, sometime in the past, have been covered in forest, or at the bottom of a sea? They will probably suggest that it has changed over time; then ask them for the evidence of change, not only in Qatar but everywhere. They will probably suggest things like fossil evidence.

Show them a globe of the world as it is now and ask what must have changed. Ask questions such as ‘How did sand get to the Sahara desert?’ Draw their attention to the shapes of Africa and South America, which seem to fit together like jig-saw pieces. Ask what that suggests.

The important outcome of this session is that it should be clear that the Earth has changed in the past and is continuing to change. The rest of this topic will cover this process.



Making a geological timescale Start questioning the class about how old things are. Start with things close to them, such as their family. Ask about how long ago the earliest person they have ever read about lived. Start placing these incidents on a timescale on the board or OHP that has the present day at one side.

Then ask about other things they may have heard of that happened much longer ago (e.g. the Ice Age, the age of the dinosaurs). Place these on the scale. The class will realise that the scale on the board or OHP is not long enough and that if a geological timescale is to be made, the events since humans have been on the planet will occupy a tiny part at the recent end.

To make a geological timescale, you will need a sheet of paper 15 m long that will go around at least two sides of the room. Label the scale every 100 million years (allow about 30 cm on the scale for each 100 million years). Label the eons and eras; although it is not necessary that students should remember these names, they may be interested in them and some, like Jurassic, they may already know.

Assign a specific section of the timescale to each group and ask them to find out about it and to make a (pictorial) display on their part of the scale that tells everyone what was happening around that time. Agree on the nature of the important events that should be displayed, such as: the appearance of humans; the first mammals (or reptiles, amphibians, birds, fish); the first vertebrates; the time of the dinosaurs; the first flowering plants; the first plants; the first bacteria; the origins of the Qatar gas field; the last Ice Age; the formation of the Earth.

You may need some resource materials on when different geological events happened. There are many useful sites on the Internet that will provide this information.

A 15 m sheet of paper can be made from many A4 sheets or you can ask a local newspaper printer for some end-of-roll newsprint that they have not used.

Enquiry skill 7.3.1

Lesson plan 7.4

Volcanoes and earthquakes Ask the class what they know about recent earthquakes or volcanoes, or famous ones in the past. Encourage them to share their knowledge. Be ready with some interesting facts about famous volcanoes to add to the debate. Ask them what volcanoes tell us about conditions inside the Earth. Show them video clips of volcanoes and animations that show how volcanoes form and explode. Illustrate the process with a poster on the board.

Discuss the concept of plate tectonics with more advanced students. Point out how volcanoes are often found above places where one tectonic plate is moving under another, generating a lot of heat due to friction. This is released in the form of volcanic activity. Show how volcanoes often occur in rows along such plate boundaries.



The structure of the Earth Show a diagram or a model of the structure of the Earth. Discuss evidence for the structure; students will know about the magnetic field of the Earth that implies an iron core. In Grade 9 they will learn more about how the way that shock waves from earthquakes travel around the Earth tells us much about the Earth’s internal structure. The important feature of the structure that they should understand is that there is a solid crust, which is floating on top of molten rock called magma. This is a key element in the rock cycle that they have studied above.

Encourage more advanced students to study the concept of continental drift and plate tectonics. Ask them to search the Internet for information about how continents have moved in the past and how they are still moving. They should find out about the supercontinents (and evidence for them) of Pangea, Laurasia and Gondwana. Animations are available on the Internet showing how these have split up and how, in particular, the break-up of Gondwana has led to the distribution of continents that we see today.

There is much good pictorial information, including animations, on the Internet; ask students to incorporate this into an ICT-based report on this topic.

More advanced students can also carry out research into how plate movement caused the Asian tsunami of December 2004.

ICT opportunities: Use of the internet; use of animations to show plate movement and to show continental drift; use of display software to prepare a report incorporating animations.

Wikipedia shows continental drift using an animation, and a particularly good animation showing the break-up of Gondwana and the formation of the present continents can be downloaded from kartoweb.itc.nl/gondwana/index.asp


Assessment


Analysis of the texture of a rock gives information about the conditions in which the rock formed.

• Crystalline textures form when liquid cools and solidifies or rocks are heated while remaining in the solid state or water evaporates from a solution.

• Fragmental textures form when pieces of rock or animal shell are cemented together.

• Foliated textures form when crystals grow inside solid rocks in the direction of least pressure.

a. Use this information to complete the table on the right. Place a in the correct box or boxes in each row.

b. Volcanic rocks are formed from lava. An intrusion forms when magma flows into other rocks and then cools down. Describe and explain the difference in the crystalline texture of volcanic rock and rock formed from an intrusion.

Igneous Metamorphic Sedimentary

Most of these rocks have a crystalline texture

Most of these rocks have a fragmental texture

These rocks have foliated features

c. Obsidian is a glass-like volcanic rock which can form under water. It contains no crystals. Suggest why obsidian contains no crystals.


The list below gives some processes which occur in the rock cycle.

1 Grains of sediment washed down by rivers collect in layers on the sea bed.

2 Large crystals form as molten magma cools deep below the Earth’s surface.

3 Layers of rock are compressed and melted as they are drawn down into the magma.

4 Grains of sediment are cemented together as they are buried deep under thick layers of other sediments.

5 New crystals form in layers as rocks are affected by high temperature and increased pressure deep in the Earth’s crust.

6 New minerals form with flat crystals when layers of mudstone are squeezed.

a. Draw a diagram of the rock cycle showing the three types of rock: igneous, metamorphic and sedimentary. Indicate the approximate place in the cycle of these events by placing the number in your diagram.

b. Give the numbers of two steps that could lead to the formation of sandstone and a further step that could lead to the formation of quartz.


Give two pieces of evidence that suggest that the part of the Earth’s surface where Qatar now is was once under the sea.

Unit 7E.1

119 | Qatar science scheme of work | Grade 7 | Unit 7P.1 | Physical processes 1 © Education Institute 2005

GRADE 7: Physical processes 1

Measurement and density

About this unit This unit is the first of five units on physical processes for Grade 7. All the other units require competency in the basic techniques studied here.





Previous learning To meet the expectations of this unit, students should already be able to distinguish between mass and weight. They should be able to measure accurately, using the correct units, the mass and volume of solids and liquids.

Expectations By the end of the unit, students measure length and mass, calculate derived quantities, and express large and small units correctly using appropriate prefixes. They understand and use the concept of density. They make estimates of size and quantity that they then check by accurate measurement.

Students who progress further calculate the density of irregular solids and understand and use the principle of Archimedes. They understand the need for accuracy and know how to achieve it.

Resources The main resources needed for this unit are: • density blocks or a materials kit containing regular shaped blocks of

different materials • top-pan balance • metre rules, trundle wheel, callipers, screw gauge, graticule • round-bottomed flask with tap, vacuum pump • helium balloon

Key vocabulary and technical terms Students should understand, use and spell correctly:

• estimate, measure • mass, volume, density • upthrust, weight • float, sink • common prefixes, such as: nano, micro, mega, giga

UNIT 7P.1 8 hours





7.17.1 Measure mass and length, use correctly the units of mass (kilogram) and length (metre), and calculate derived quantities, such as area and volume of regular objects.

7.17.2 Express large and small units correctly using appropriate prefixes

7.17.3 Calculate the density of liquids, gases and regular and irregular solids.

6.14.3 Distinguish between mass and weight.

7.17.4 Know that the weight of an object is less in water because of the upthrust of the water acting on it.

7.17.5 Know that the difference in weight of an object when it is lowered into water is equal to the weight of the water displaced by the object.

7.17.6 Know that air also causes upthrust and explain why helium and hot air balloons rise in the air.

7.1.3 Make estimates of size and quantity, and check estimates against accurate measurement.

7.1.4 Understand the importance of accuracy and use techniques such as repetition of measurements to ensure it.

9.1.6 Estimate margins of error and know how these affect their results.

3 hours

Measuring mass and length and calculating derived quantities

2 hours

Large and small things

3 hours

Density

6.3.2 Measure accurately, using the correct units, the mass and volume of solids and liquids.

7.4.3 Use a trundle wheel, tape measure, ruler, callipers and micrometer for measuring lengths to an appropriate degree of accuracy.

Unit 7P.1


Activities


Introduction The first part of this unit allows you to ensure that all students have mastered basic measurement skills in their earlier years; these skills are essential for work in later units.

Set a number of small tasks measuring the mass and length of everyday objects using a balance and a metre ruler. You should measure them accurately beforehand so that you can quickly check their work. In all the work in this unit, all students should have an opportunity to learn how to use the equipment even though they will work collaboratively in groups. They should all record all the measurements they make.

Teach more advanced students how to use a tare facility of a balance so that they can learn to weigh the contents of a container.


Estimating Estimating is a useful scientific technique. Assist students to develop their estimating skills by asking that all measurements made in this unit are first estimated and then measured. Tell students that they should always write their estimates in their books as they make them.

Enquiry skill 7.1.3

Use of callipers and a micrometer screw gauge Set tasks, such as measuring the diameter of an orange, that allow students to learn how to use callipers. Demonstrate how to do it first.

Teach more advanced students how to use the micrometer screw gauge. Demonstrate how to do it first and give students a set of pictorial instructions that they can consult if necessary. Set suitable tasks for which a micrometer is essential, such as measuring the diameter of different wires.

Students will need instructions on using the micrometer screw gauge.

Enquiry skill 7.4.3

3 hours

Measuring mass and length and calculating derived quantities. Measure mass and length, use correctly the units of mass (kilogram) and length (metre), and calculate derived quantities, such as area and volume of regular objects.

Understand the importance of accuracy and use techniques such as repetition of measurements to ensure it.

Make estimates of size and quantity, and check estimates against accurate measurement.

Use a trundle wheel, tape measure, ruler, callipers and micrometer for measuring lengths to an appropriate degree of accuracy.

Accuracy Ask the class for suggestions on how they might ensure that their readings are as accurate as possible. (Students will, probably unknowingly, confuse accuracy and precision. You do not need to address this confusion at this stage, though you could discuss the difference between the two with advanced students, such those who learn to use the micrometer.)

Ideas that should emerge and be stressed are: • the desirability to make measurements several times, preferably the same measurement

made several times by different people; • the need to check measurements that might be suspect for any reason (e.g. if a

measurement is very different from others made on similar objects); • how to take an average of several measurements; • (for more advanced students) the meaning of significant figures when working out results.

Enquiry skill 7.1.4

Unit 7P.1



Selection of the appropriate measuring instrument The enquiry standards put increasing stress through the grades on selecting the appropriate tools for carrying out a procedure. Discuss with the class what might be the most appropriate tools for measuring different lengths, ranging from objects that are less than a millimetre across (the diameter of a pin) to those that are several kilometres long (the length of the Corniche in Doha). Let students carry out some of the measurements using the correct instruments, including trundle wheel, tape measure, ruler, callipers and micrometer.

Area and volume Show students how to calculate area and volume. Set a number of tasks that ask students to measure the dimensions of common regular objects and then calculate their area or volume (e.g. the area or their workbook or the volume of their desk).

Students should already have been taught area and volume in a manner that emphasises the concepts. If this has been done, work in science can simply reinforce the use of the techniques. You may wish, however, to spend rather more time on this and allow students to work individually on the concepts through tasks that use sets of specialised equipment.

Teach the correct way of writing all units and insist on their correct use in all written work.

You will need sets of equipment for teaching area and volume.

Measurements using the human body Get students, in class, to take and record such measurements as their height and mass, and then collate them. This allows you to teach distribution charts as a whole class activity while at the same time teaching about making measurements. This can be extended to measurements such as knuckle length and vital capacity. Exercise care though – some pupils may be sensitive about their height or mass if these are significantly different from the majority.

Enquiry skill 7.3.3

Challenges Set a number of challenges (for homework), such as: • measure the thickness of a page in a telephone directory; • think of a way of measuring the mass of the air in a room.

Introduction Ask students about the smallest and largest lengths that they can think of. Make a list on the OHP or board that includes the approximate size of the lengths. It will become evident that a variety of units are needed to accommodate the range suggested. Students will already be aware of some that they have met in mathematics.

Give them a table showing the relationship between millimetres, centimetres, metres and kilometres. Set some conversion tasks, demonstrating one or two and going through some at the end. These tasks can be done at home. Set similar tasks with units of mass after first allowing students to see and handle masses from 1 mg to 5 kg or more.

Sets of masses can be purchased. You can make objects that have an exact mass of 10 mg, 100 mg, 1 g, etc. You can make up sandbags that have masses above 0.5 kg.

2 hours

Large and small things Express large and small units correctly using appropriate prefixes.

Use a trundle wheel, tape measure, ruler, callipers and micrometer for measuring lengths to an appropriate degree of accuracy.

Smaller and larger units Introduce some of the smaller and larger units of length and mass so that students become familiar with the more common prefixes nano, micro, mega and giga and are aware of many others. Provide them with tables to show the relationships between the units.

It is undesirable to use scientific notation at this level



Using a graticule Allow students, in groups, to use a graticule in conjunction with a powerful hand lens or microscope to estimate and measure objects too small to measure with the naked eye, such as the thickness of a hair.

This section may be partly delayed until students learn how to use a microscope later in the year.

A distance chart Ask students to construct, in their books or as a display, a distance chart that shows examples, in pictorial or diagrammatic form, of objects whose dimensions range from nanometres to gigametres. The chart could look like a ladder with each successive space between the rungs devoted to a different unit prefix. The space would contain illustrations of a number of different objects whose dimensions are a small number of the particular unit prefix. The nanometres box could contain representations of atoms, the micrometres, pictures of bacteria, the megametres, photographs of the Earth, and so on.

ICT opportunities: Some students may wish to use display software for this exercise. Illustrations can be downloaded from the Internet.

Enquiry skill 7.3.3

Density of regular solids Discuss the idea of whether a substance is ‘heavy’ or ‘light’. Illustrate this by preparing two boxes, a large one and a heavier smaller one. Ask students to hold them and say which feels heavier. (This is more interesting when three different boxes are prepared as it stops students trying to guess what you want them to say). Lead the discussion to the conclusion that to compare the ‘heaviness’ of substances we need to compare identical volumes. We can choose the volume as 1 cm3.

Ask students, in groups, to measure the dimensions and the mass of a variety of regular solids, tabulate the results and calculate their densities. Alert students may note that all objects that float in water have a density that is less than one. This can be discussed.

Encourage more advanced students to measure the volume of irregular solids by water displacement and so calculate their density.

The correct way or writing the units of density should be taught and insisted upon.

Materials kits are available which contain samples of materials from lead to polystyrene that are rectangular with dimensions in integers of centimetres.

At this level, density is best taught in terms of the mass of 1 cm3. Leave the SI unit until later.

3 hours

Density Calculate the density of liquids, gases and regular and irregular solids

Know that the weight of an object is less in water because of the upthrust of the water acting on it.

Know that air also causes upthrust and explain why helium and hot air balloons rise in the air.

Densities of liquids and gases Adapt the work done in the previous activity to find the density of common liquids such as water, cooking oil and methylated spirits. If students can use a tared balance, this can be done easily using a 10 or 100 cm3 measuring cylinder on a balance pan.

Note particularly that the density of water is 1 g/cm3. This may be linked to observations made above on floating and sinking in water.

Demonstrate the determination of the density of air. Prepare a round-bottomed flask for evacuation. Weigh the whole set of equipment, including the flask, bung and taps. Evacuate it and reweigh to find the mass of air removed. Open it under water and allow water to be sucked in. The volume of air evacuated is equal to the volume of air sucked in. From these results the density can be calculated. Write all results and the calculation on the board or OHP. Finish by calculating the mass of a cubic metre of air (about 1.2 kg).

Students can then be asked to estimate the volume of various rooms (also at home or at the mosque) and to calculate the mass of the air in them (see the challenge at the end of the previous section). They will be quite surprised by the results.

Use a 1000 cm3 round-bottomed flask. You can use any kind of pump to evacuate it, but an oil vacuum pump is best. The mass must be measured to an accuracy of 1 mg if possible and certainly 10 mg; 100 cm3 of air weighs a little over 0.1 g.

Safety: All work involving the evacuation of glassware should be demonstrated behind a safety screen.



Floating and sinking Recall work done in Grade 6 on weightlessness. Ask students to classify the objects used in the section on the density of regular solids according to whether they float or sink in water. Students should tabulate their observations and draw some simple conclusions about what kinds of objects float and what sink.

Provide groups with a bucket of water and a variety of objects that can be suspended from a forcemeter. Ask them to measure the weight of the object in and out of the water and tabulate the results. Ask them to calculate the upthrust on each object and write it in the table. Challenge them to draw a conclusion about the relationship between upthrust and weight (out of water) of floating objects.

Repeat the activity, using the same objects, with seawater or salt water. Note the difference in results.

Encourage more advanced students to make lines on the objects so they can note how deeply the objects float in the two water samples.

You could also introduce more advanced students to Archimedes’ principle. Ask groups to lower objects suspended on a spring balance or a beam balance (i.e. calibrated in grams, not newtons) into water in a measuring cylinder, and note the correspondence between the apparent loss in mass and the volume (and hence mass) of the water displaced.

Ask students to make, at home, a jam jar that contains three layers of liquid: syrup, water and cooking oil (tell them they need to put the layers in very carefully. Challenge them to find something that will float on each layer. A second challenge could be to make a fresh egg float in the middle of a jar of water. This is described in Unit 6P.1.

Refer to weight as a force and work in newtons throughout. You may prefer to work throughout in terms of weight (newtons) and compare the loss in weight with the weight (in newtons) of the displaced water.

Displacement cans can be used for this experiment.

Floating and sinking in air If possible, acquire or make a helium-filled balloon to show upthrust in air. Discuss why the balloon rises. Ask students to predict a value for the density of helium given that the density of air that they worked out is about 1.2 kg/m3.

You could also use a hydrogen-filled balloon. The mass of1000 cm3 of helium is 0.18 g and of hydrogen, 0.09 g.

Floating and sinking applications Ask students to explain how it is possible to make large ships out of steel, which is more dense than water, and yet they float.

Get students to prepare a display on applications of floating and sinking, either individually in their books or as a class display of materials that students generate or collect. They could use display software.

ICT opportunity: Use of display software and materials from the Internet.


Assessment


Here is a list of instruments for measuring length:

• graticule;

• metre ruler calibrated in millimetre divisions;

• micrometer screw gauge, 50 m tape measure;

• trundle wheel;

• 30 cm ruler calibrated in 0.5 mm division.

Which would you use to measure the following distances?

a. The distance travelled by a snail in 5 minutes.

b. The diameter of a wire.

c. The circumference of the school grounds.

d. Your height.

e. The width of a line ruled on lined paper.

f. How far you can run in 10 seconds.

A rectangular solid has a mass of 12 g and dimensions 2 cm, 3 cm and 4 cm. What is the density of the solid?

A liquid is found to have a volume of 75 cm3 in a measuring cylinder. When placed on a balance, the liquid and measuring cylinder has a mass of 140 g. The empty measuring cylinder has a mass of 65 g. What is the density of the liquid?

The diagram shows three layers of different liquids in a jar. Which of the following objects would float on top of the water layer. Explain your answer.

• Object A, density 3.2 g/cm3.

• Object B, density 1.1 g/cm3.

• Object C, density 0.9 g/cm3.

• Object D, density 0.6 g/cm3.

Some ships coming into ports in Qatar have lines, called Plimsoll lines, on them that show the level of the sea along the side of the ship when they are in different oceans. Why will a ship sink deeper into the water in one ocean than another?


You are given two pieces of metal that look the same. One of them is pure copper and the other may be contaminated with some zinc, which is less dense than copper. Devise an investigation that would tell you whether the copper in the second piece contains zinc or not.

Enquiry skill 7.1.1

Unit 7P.1



Electrostatics

About this unit This unit is the second of five units on physical processes for Grade 7. This unit is required before current electricity is studied in Unit 7P.5.


The teaching and learning activities should help you to plan the content and pace of lessons. Adapt the ideas to meet your students’ needs. For consolidation activities, look at the scheme of work for Grade 5.



Previous learning To meet the expectations of this unit, students should already be aware that static electricity is a force that acts at a distance and that a charged object can attract uncharged insulators and attract or repel other bodies that are statically charged.

Expectations By the end of the unit, students know the origins of electrostatic charge and know how charged objects interact. They use an electroscope to detect and identify charge and know the origin of lightning.

Students who progress further explain a variety of natural electrostatic phenomena. They explain how an electroscope detects charge and know how a Van de Graaff generator works. They cite and explain some important applications of electrostatics.

Resources The main resources needed for this unit are: • a range of samples of solid materials, such as plastics, wood and metals • samples of cloth and fur • electroscopes and basic electrostatics equipment • Van de Graaff generator and standard accessories

Key vocabulary and technical terms Students should understand, use and spell correctly: • static electricity, positive charge, negative charge • charging by friction • attraction, repulsion • neutralisation of charge, discharge, • electroscope • Van de Graaff generator • lightning, thunder, point discharge

UNIT 7P.2 7 hours





5.13.1 Know that electrostatic charge is generated by friction when an insulator is rubbed and that two kinds of charge can be created in this way.

7.18.1 Know that electrostatic charges are caused by friction when an insulator is rubbed, that two kinds of charge, positive and negative, can be created in this way and that unlike charges attract each other and like charges repel.

7.20.1 Know that electricity requires a complete circuit to flow.

7.18.2 Explain the movement of the gold leaf when an electroscope is used to detect charge.

7.18.3 Know that lightning is an electrical discharge caused by a static charge that results from friction between moving air masses, and that it can be dangerous.

4 hours

Basic electrostatics

3 hours

Electrostatic discharge

7.18.4 Show that electrostatic charges discharge most easily at a point and know some applications of this, such as pointed lightning conductors.

Unit 7P.2


Activities


Everyday experiences of static electricity Demonstrate a number of simple everyday experiences of static electricity. Rub a balloon on the wall; it will stick there. Take two strips of polythene cut from a shopping bag and pull them between your fingers; they will immediately fly apart. Rub a plastic ruler with fur or woollen fabric and place it next to a gently flowing tap; the water will be attracted to the ruler. Ask the class for other examples.

It is important that the origins of electrostatic phenomena in friction between materials is made clear.

Static electricity should be taught when the atmospheric humidity is low. The best time will be when the weather is dry during winter.


What kinds of substance become charged? Provide groups of students with a number of solid materials and some cloths to rub them on (wool or fur is best). The materials should include some metals and some plastics. Ask students to make some small bits of paper (less than 1 cm2). Tell them to rub each material in turn with the cloth and see whether it will pick up some of the small bits of paper. Ask students to write down their observations in a two-column table: one column for materials that become charged and one for those that do not. Tell them to look at the two groups and see whether there are any patterns. They will see, for example, that substances such as plastics and glass become charged while metals do not.

Provide groups with a variety of plastics, wood and metals.

4 hours

Basic electrostatics Know that electrostatic charges are caused by friction when an insulator is rubbed, that two kinds of charge, positive and negative, can be created in this way and that unlike charges attract each other and like charges repel.

Explain the movement of the gold leaf when an electroscope is used to detect charge.

Using an electroscope Ask each group to clamp a metal ruler using a wooded clamp. Hang a piece of thin aluminium foil folded in an inverted V-shape over the other end. Ask students to touch the ruler with a charged rod; the aluminium foil leaves will move apart. Ask students to explain why the leaves moved apart. Conclude that static electricity can cause both attraction and repulsion.

Use a commercial electroscope to demonstrate the detection of charge on charged rods. Students will notice that, when the leaf is raised and a charged rod is brought near to it, sometimes the leaf will rise further and other times it will fall. Ask for explanations. Conclude that there must be two kinds of electrical charge, which are called positive and negative. Leave the detailed explanation until after the next activity.

Show advanced students how to charge an electroscope by induction.

Unit 7P.2



Electrostatic attraction and repulsion This activity requires a set of rods that charge up positive and negative, preferably colour coded red and black. The usual modern materials are polythene and acrylic; the classic materials are ebonite (a natural resin) and glass. It should be possible to balance the rods on a pivot or suspend them from a stirrup so they are free to move. Ask students to work in groups to devise an investigation to show how the differently charged rods interact when one is brought near to another. Tell them to produce a table of results to show all possible interactions. Ask them to draw a conclusion from the investigation, and they will realise that rods that are similarly charged repel each other while those that are oppositely charged will attract each other.

Now give a further explanation of the action of friction to generate static charge: the charge on the object that is rubbed will be balanced by an equal and opposite charge on the cloth or fur used to rub it.

Explaining the electroscope Demonstrate charging by contact with a rod of known charge. Ask groups to bring a rod of the same charge near to, but not touching, the electroscope. Then bring up a rod of opposite charge and note the difference. Explain to the class, using diagrams of the charge distribution, why the leaf rises initially and what happens to the charge distribution when the charged rods are brought near to the electroscope. They should then be able to use the electroscope as an instrument for identifying the type of charge on an object.

Ensure that good contact is made and check that the charge on the electroscope is not the opposite to that on the rod.

3 hours

Electrostatic discharge Know that lightning is an electrical discharge caused by a static charge that results from friction between moving air masses, and that it can be dangerous.

Show that electrostatic charges discharge most easily at a point and know some applications of this, such as pointed lightning conductors.

Lightning in the classroom Ask the class to recount some of their experiences with static electricity. They may have felt a shock as they stepped out of a car and then touched the outside of the car door to shut it. They may have felt a shock when they touched something like a doorknob after sitting on plastic chairs on a carpet. They may have heard and even seen sparks when they take off a woollen jumper or pullover. Note all the experiences and try to explain them through the next activities.

Quite a large charge can be accumulated on an aluminium plate on top of an expanded polystyrene tray of the kind used in supermarkets. Ask groups of students to try out this activity or set it as practical homework. Tell them to make an insulated handle for the plate out of some polystyrene, rub the tray with fur (or clean dry hair or wool) and place the plate (holding it by its insulated handle) on top of it on the table. Sparks may be heard, and sometimes seen, when they bring a finger close to the edge of the plate. Ask the class whether it works as well if they bring their finger near to a flat part of the plate (link to point discharge below). After the plate has been discharged, tell them to lift it away from the polystyrene and to bring their finger near to its edge again; another spark will be heard.

Challenge the class to give an explanation of both sparks. Summarise what is happening for more advanced students, using drawings on the board or OHP.

The charge on the tray induces an opposite charge on the part of the plate near the tray, leaving the far edge of the plate with an induced charge the same as on the tray. This charge is neutralised when earthed. When the plate is lifted off the polystyrene, the charge near the polystyrene will now distribute itself over the whole plate and can be earthed to produce the second spark.



Van de Graaff generator Use the Van de Graaff generator and its accessories to demonstrate a variety of phenomena. The gas tap can be used as an effective earth when necessary. Phenomena that can be studied are: • electrical discharge in air (approximately 30 000 volts per cm); • discharge at a point; lighting a neon discharge bulb; • the distribution of charge in a metal container (Faraday’s ‘ice pail’ experiment); • repulsion between similarly charged objects (the ‘head of hair’ experiment); • (advanced students) how the Van de Graaff generator works.

At the end of the demonstration, make sure students have a list of the properties of static electricity that have been demonstrated and, where possible, link the demonstration to real life experiences, such as the build up of charge (on the outside only) of a car moving through air, so that the charge is felt only when you close the door after getting out.

Safety: The Van de Graaff generator produces high voltages on a dry day. Care must be exercised if students are to be exposed to the voltages.

The generator and its accessories kit will contain instructions for the safe execution of a variety of demonstrations.

Lightning Show pictures of lightning. Download some video clips from the Internet. Discuss, using diagrams, the origins of lightning as a result of friction between air masses. Discuss the origin of the sound and why the lightning is seen before the thunder is heard.

Discuss the design of lightning conductors on tall buildings and masts.

Applications of electrostatics Encourage more advanced students to study some everyday applications of electrostatics, such as laser printers and photocopiers. Ask them to find out from the library or the Internet how such devices work and to report to the class. Discuss the origin of the smell of ozone associated with photocopying (and the need for photocopying rooms to be well ventilated).

Discuss the need to protect delicate electronic components from accidental electrostatic damage. Two aspects in particular could be relevant for the students: • the use of conducting plastic packaging for electronic components, such as SIM cards and

computer components; • the importance of not touching the conducting parts of computers and mobile phones unless

you are earthed.

ICT opportunity: Use of the Internet. www.howstuffworks.com has clear explanations of how laser printers and photocopiers work.


Assessment


Saif hung a small polystyrene ball (ball A) on a nylon thread and charged it negatively. Describe one way that he could have used to charge it. He has a second ball (ball B) on the end of a straw that he has also charged. He brings ball B near to ball A, which is repelled. What is the charge on ball B? Explain your answer.

Saif now neutralises the charge on ball B. How could he do this? He then brings the uncharged ball B up to ball A. What will happen to ball A? He then touched ball A with ball B and ball A was immediately repelled from ball B. Explain why this happened.

The diagram represents a conductor. It has equal numbers of positive and negative charges. In the diagram, the + signs and the – signs are shown throughout the conductor. This represents the pattern of positive and negative charges in a real conductor. Why are the charges spread out instead of forming areas of positive charge and areas of negative charge?

A negatively charged object is brought near to the conductor. This changes the position of charges in the conductor. Draw the new pattern of positive and negative charges in the conductor. Why does the pattern of positive and negative charges change in this way?

QCA Key Stage 3, 1998, level 6, part question

Explain the following observations:

a. In dry weather, if you stand in front of a mirror in the dark as you take off a woollen cardigan, you sometimes see sparks.

b. Lightning often strikes trees or tall buildings.

c. Sometimes you can get an electric shock by touching the outside of a car door as you get out.

d. When you comb your hair in dry weather, the hair sometimes sticks to the comb.

e. You can stop hair sticking to the comb by making the comb wet.

f. In dry weather, computer repair engineers often wear a metal bracelet connected by a wire to the metal case of a computer when they are removing electronic items.


Design an investigation into the factors that affect how long a balloon will stick electrostatically to surfaces.

Enquiry skill 7.1.1

Unit 7P.2



Magnetism

About this unit This unit is the third of five units on physical processes for Grade 7. It builds on Unit 6P.1 and leads on to work on electromagnets in Grade 8.





Previous learning To meet the expectations of this unit, students should already be aware that magnetism is a force that acts at a distance, that magnets attract objects that contain iron, and that they can attract and also repel other magnets

Expectations By the end of the unit, students distinguish between magnetic and non-magnetic materials and make a permanent magnet They recognise that the Earth has a magnetic field. They demonstrate the field pattern around a magnet, distinguish between the north and south poles, and know that magnetic fields act through non-magnetic materials but not through magnetic ones.

Students who progress further explain magnetic phenomena in terms of ‘molecular magnets’. They make electromagnets. They recognise that magnetic lines of force have direction and that fields from different sources interact but the lines do not cross.

Resources The main resources needed for this unit are: • basic equipment for teaching magnetism, including a variety of different

kinds of magnets • a variety of magnetic and non-magnetic materials for testing • pins, nails, paper clips. • hacksaw • Internet access

Key vocabulary and technical terms Students should understand, use and spell correctly: • magnetism, magnet, magnetic, magnetised • iron, steel • compass, compass needle, plotting compass • magnetic pole, geographic pole • lines of force

UNIT 7P.3 8 hours





7.19.1 Distinguish between magnetic and non-magnetic materials.

7.19.2 Distinguish between an object that is a magnet and one that is attracted to a magnet but which is not itself a magnet. Know how magnets can be made and understand that the test for magnetism is repulsion.

7.19.3 Recognise that the Earth has a magnetic field and realise that the Earth’s south magnetic pole is in its geographical north and vice versa.

6.14.1 Distinguish between forces that act at a distance (such as gravity, magnetism and electrostatic force) and contact forces.

7.19.4 Distinguish between the north and south poles of a magnet and know that similar magnetic poles repel each other and opposite poles attract each other.

7.19.5 Demonstrate the pattern of the lines of force of a magnetic field around a magnet using both iron filings and plotting compasses.

8.19.1 Know that a coil of wire carrying a current produces a magnetic field similar to a bar magnet; list the factors affecting the strength of an electromagnet.

3 hours

Magnets

5 hours

Magnetic force and fields

7.19.6 Know that magnetic fields act through non-magnetic materials.

Unit 7P.3


Activities


Introduction Ask students to recall earlier work to discover what they already know about magnetism. List points on the board or OHP. This unit provides opportunities for students to consolidate the work they have done so far and will involve some repetition of earlier work in different ways.

Ask students to list the kinds of magnets they know about and what they are used for. Show students a collection of different types of magnets and allow them to test them to find out what they can about them.

This can form the beginning of a display on magnets and their uses. Encourage the students to bring a variety of magnets into school and test them (see below) and display them. Also ask them to find some pictures of the use of magnets on the Internet. Challenge them to find pictures of the largest and the smallest magnet.

An important conclusion is that most magnets are made from, or contain, steel. Steel is mainly iron, which is the most common element that can be magnetised. The existence of ceramic magnets and of plastic fridge magnets can cause confusion and this should be discussed; both contain iron metal in powder form.

Save magnets from various devices, such as loudspeakers, motors and toys. Have available some magnets that appear not to be made out of steel, like ceramic fridge magnets and magnetic strips and pads.

ICT opportunity: Find pictures of large and small magnets on the internet


What is attracted to a magnet? Provide groups of students with some magnets and ask them to make two lists: things that are attracted to a magnet and things that are not. Ask students to draw conclusions from the lists, one of which should be that only things that are made from steel are attracted to a magnet.

Clarify the meanings of the words magnetic and magnetised.

Clarify the difference between iron and steel. All the substances they test that are attracted to the magnet will be made from steel, but it is the iron in the steel that is attracted.

How strong is a magnet? Challenge the groups to devise an investigation that compares the strength of different magnets and provides results that can be displayed graphically. There are may ways of doing this. A simple one is to find out how many standard paper clips can be suspended from a pole of the magnet and to represent the length of the clip chain in a bar chart.


3 hours

Magnets Distinguish between magnetic and non-magnetic materials.

Distinguish between an object that is a magnet and one that is attracted to a magnet but which is not itself a magnet. Know how magnets can be made and understand that the test for magnetism is repulsion.

Making a magnet Show the students how to make a bar magnet out of a large nail by the stroking method. Ask them each to make a magnet and find out whose nail will pick up the longest chain of paper clips.

Find out the effect of heating the nail in a Bunsen flame or knocking it hard against something: both will destroy the magnetism unless the nail is made of hardened steel.

More advanced students can make an electromagnet from a large nail with insulated wire wound around it. They can also be taught an explanation in terms of ‘molecular magnets’ of why magnets can be demagnetised by heating and knocking.

Unit 7P.3



Does a magnetic field act through other materials? Recall (or repeat) the short demonstration at the start of Unit 6P.1 in which the magnetic ‘force’ was ‘cut’ with a pair of steel scissors.

Explain that the magnetic force is carried away from the magnet by way of the magnetic field and that the magnetic field can go through some, but not all, materials. Ask students, in groups, to find out what kinds of materials allow a magnetic field to pass and what kinds of materials stop it. Give each group a magnet, something that is attracted to it (e.g. some paper clips) and some different materials to test. Make sure that you give all groups a small sheet of mild steel as one of the materials, together with some thin sheets of other metals (e.g. copper and aluminium).

What parts of the magnet attract most strongly? Give each group a magnet and some iron filings. The magnet should be steel and either a horseshoe or a bar magnet; it should not be too strong. They could use the nail magnet that they have made (above). Ask them to sprinkle the filings on the magnets and note what parts of the magnets they stick to. The filings stick only to the poles at the ends of the magnets. Tell students to draw a picture of the magnet in their books, together with their conclusion.

An interesting extension of this is to ask the group to saw their nail magnet in half and test the two halves. Each half becomes a magnet and new poles are created where the nail was sawn.

Iron filings are very difficult to remove from strong magnets such as ceramic magnets.

It is best to saw the nails almost in half before they are magnetised, as the process of sawing can partially destroy the magnetism. If the nail is almost cut through, they can break it in half.

Magnetic poles Suspend a bar magnet from some cotton and bring a second one up to it. Challenge students to explain what they observe. They should understand that each magnet has two poles that we call north and south (see below) and that opposite poles attract each other but poles that are the same will repel.

At this stage challenge them to develop a test that will tell them whether or not a piece of steel is a magnet or not. Hand them some nails, some of which have been magnetised, and ask them to distinguish between those that are magnets and those that are not.

Tell them to write the test for magnetism that they have developed in their books. Check that they have correctly noted that the test for a magnet is whether another magnet will repel any part of it.

Challenge groups to find the poles on unusually shaped magnets, such as those from old loudspeakers or small motors.

5 hours

Magnetic force and fields Demonstrate the pattern of the lines of force of a magnetic field around a magnet using both iron filings and plotting compasses.

Recognise that the Earth has a magnetic field and realise that the Earth’s south magnetic pole is in its geographical north and vice versa.

Distinguish between the north and south poles of a magnet and know that similar magnetic poles repel each other and opposite poles attract each other.

Know that magnetic fields act through non-magnetic materials.

The magnetic field of the earth Ask groups of students to hang a bar magnet up so that it is free to rotate (or place it on a cork floating on water) and allow it to come to rest. Ask groups to check each other’s work and demand an observation and possibly an explanation. All the magnets will be pointing the same way, suggesting that they are lining up in an existing magnetic field. They will line up in a north–south orientation. If the magnets have their north poles marked, students will notice that they always come to rest pointing towards the north.

Explain that this is caused by the magnetic field of the Earth, which has a core made mainly of iron. (Advanced students may take this a little further and relate the field to the movement of the core, an idea that will be covered in Grade 9.) Explain that the poles of the Earth’s magnet are near the geographical poles. Ensure that students understand that the pole of the Earth’s

Use an unspun thread such as nylon filament to avoid the magnet turning because of movement by the thread. The magnets should be hung from a wooden stand well away from anything made of steel.

Note that magnets, particularly small compass needles, often become magnetised the wrong way around if they are left near a much more powerful magnet. Check the polarity of such magnets regularly to avoid confusion.



magnet that is near the geographical north is a south pole because it attracts the north pole of the bar magnets. This idea commonly leads to some confusion and time should be spent on it.

Introduce the idea of a compass needle as a small pivoted magnet that points in a north–south direction. Show, if possible, a ship’s compass that always works even when the ship is pitching in the sea.

Show more advanced students the dip circle to illustrate the Earth’s field in three dimensions. Explain that the angle of dip varies according to where they are on the Earth’s surface and that the nearer to the poles the measurement is taken, the steeper the angle becomes. This can be explained after the next section on the shape of magnetic fields.

Making a model showing the Earth’s magnetic field Ask students to make (at home) a model of the Earth with a magnetised nail through it (nail south pole near the geographic north pole). The direction of the field on the surface of the model can be explored with a small compass. The Earth model can be made from any suitable materials. A hollow ball can be made from papier-mâché on the surface of a small inflated balloon, which can be deflated when the paper is dry.

The shapes of magnetic fields The shape of the field of a bar magnet can be shown easily in two ways. The simple way is to sprinkle iron filings on top of a sheet of paper placed on top of the magnet. Tapping the paper gently allows the filings to line up following the lines of force. The second way is to plot the field using a plotting compass. Demonstrate each method to the class in outline first, and then allow each group, or individual, to try both using a bar magnet. Groups in difficulties will require help. Give groups that finish first a different shaped magnet (e.g. a horseshoe magnet) to investigate.

Consolidate the work with diagrams on the board or OHP showing that magnetic fields consist of ‘lines of force’ that run from one pole to the other. More advanced students will recognise that these have direction, running from the north to the south poles. Ask more advanced students to plot the fields of two magnets placed at various orientations to each other to find out how the fields interact and how they can give rise to neutral points; they should also observe that although the lines of force interact, they do not cross.

An extension of the iron filings work is to plot the field on waxed paper and then seal it by carefully melting the wax with a Bunsen flame and allowing it to reset, trapping the filings. This results in a permanent record of the field.

Magnetic applications and phenomena Ask students to make a list of all the uses of permanent magnets that they can think of. Also ask them to find out about natural phenomena of magnetic origin, such as lodestone and the aurora borealis. Discuss these in class. Discussion of the aurora provides an opportunity to mention the importance to us of the Earth’s field, which deflects harmful radiation from space.


Assessment


Shahla put a paper cup into a glass beaker. She glued a magnet in the bottom of the paper cup. She glued another magnet in the bottom of the beaker so that the magnets repelled each other asin diagram A.

What two forces act on the paper cup and its contents to keep it in this position?

Shahla put 5 g of aluminium rivets into the paper cup. It moved down a little, as shown in diagram B.

She then plotted a graph to show how the mass of aluminium rivets affected the distance the cup moved down. Use the graph to find the mass that made the cup move down 4 mm. Why did the graph stay flat with masses greater than 40 g?

Diagram A Diagram B


Shahla removed the 5 g of aluminium rivets and put 5 g of iron nails into the cup. The paper cup moved down more with 5 g of iron nails than with 5 g of aluminium rivets. Give the reason for this.


Enquiry skill 7.3.3

Unit 7P.3



Ibrahim put a bar magnet next to some sewing needles. Two needles were attracted to the magnet as shown in the diagram.

a. Explain why the needles are hanging from the ends of the magnet and not the middle.

b. Why are the needles not hanging vertically downwards?

Ibrahim then placed the magnet on a cork floating on water in a plastic bowl. The cork turned slowly around and then stopped turning.

a. Explain why the cork moved and then stopped.

b. Which way was the magnet pointing when the cork stopped turning?

c. If Ibrahim had used a steel bowl, what would have happened to the cork and the magnet?

A bar magnet is cut in two with a hacksaw. Write an ‘N’ or an ‘S’ in each box to show the polarity of the cut ends.

TIMSS Grade 7–8, 1995



The effects of forces

About this unit This unit is the fourth of five units on physical processes for Grade 7.

The unit is designed to guide your planning and teaching of lessons on physical processes. It provides a link between the standards for science and your lesson plans




Previous learning To meet the expectations of this unit, students should already have a broad understanding of the nature of forces, how to measure them and their effects on stationary or moving objects. They should understand the difference between contact and non-contact forces and be able to distinguish between mass and weight. Their understanding of these issues, however, is not expected to be deep and they will have the opportunity in this unit to consolidate this understanding and address gaps in their knowledge.

Expectations By the end of the unit, students recall that all objects exert a gravitational attraction on other objects that depends on the objects’ masses and how far apart they are, and that the force of gravity due to the Earth on a 1 kg mass on its surface is approximately 10 N. They know that forces can cause objects to move and to change shape, and use the concept of centre of gravity. They represent forces in diagrams using arrows that indicate the direction and magnitude of the forces.

Students who progress further calculate the weight of a mass in several different gravitational environments and are able to estimate using diagrams the magnitude of the resultant of two forces acting on a body

Resources The main resources needed for this unit are: • video recorder and projector or TV and tapes of football and/or tennis • small springs or rubber bands to test to destruction • helium balloon • polystyrene (or card) egg box • Internet access

Key vocabulary and technical terms Students should understand, use and spell correctly: • force, newton • gravity, weight, mass, weightlessness • resultant • centre of gravity

UNIT 7P.4 9 hours





6.14.1 Distinguish between forces that act at a distance (such as gravity, magnetism and electrostatic force) and contact forces.

7.16.1 Know that all objects exert a gravitational attraction on other objects, the size of which depends on their mass and distance apart, and that the force of gravity on a mass of 1 kg on the Earth’s surface is approximately 10 N.

7.16.2 Give and explain everyday examples of how forces can cause stationary objects to move and can change the direction and speed of an object that is already moving.

9.19.2 Know that the turning effect of a force is called its moment and calculate the moment of a given force.

7.16.3 Give and explain everyday examples of how forces can cause objects to change shape.

6.15.4 Know that when forces on an object are unbalanced, there is a resultant force on it that can cause it to change its shape, speed or direction of movement.

7.16.4 Know that more than one force is acting on an object that is resting on the floor and know that these forces are balanced so that the object is stationary.

6.15.6 Represent the forces acting on a body with arrows that point in the direction of the force.

7.16.5 Represent the forces acting on an object diagrammatically, using arrows that show direction and magnitude.

7.16.6 Recognise that there may be many forces acting on an object that may not be in balance, and be able to represent them in diagrams and to make deductions about the size and direction of any resultant forces.

2 hours

Forces and how to measure them

3 hours

What forces can do

2 hours

Many forces acting on an object

2 hours

Centre of gravity

7.16.7 Know that the centre of gravity of an object is the point through which its mass appears to act.

7.16.8 Know that if the centre of gravity is not above the base of the object, the object will be unstable.

Unit 7P.4


Activities


Recall earlier work and identify gaps in understanding This topic brings together all the work done on forces in earlier grades. It provides an opportunity to revisit the ideas that students have been introduced to but in an environment where more equipment is available. Therefore the first activity should be to determine what students already know about forces (see the physical process standards for Grade 6). This can be done by a simple question-and-answer session, but perhaps a better way is by a more complex activity such as developing a concept map. Divide students into groups and ask them to produce a concept map around the word force. They will need some help with this; start them off on the board or OHP with some obvious links to, say, magnetism or newton. Repeat the concept map exercise at the end of this unit

This exercise will expose weaknesses in understanding, so be prepared to conduct short group practicals or demonstrations to address any basic misunderstandings before proceeding with the rest of the unit. These could include simple activities such as pushing objects (including ice cubes), stretching a rubber band, pulling magnets apart, dropping a marble and a sheet of paper simultaneously and weighing objects.

All students should, at the end of this topic, be able to use a forcemeter to measure forces. They should distinguish between contact and non-contact forces. They should have an intuitive feel for the size of a newton (the weight of a small apple) and they should be able to distinguish between mass and weight.


2 hours

Forces and how to measure them Know that all objects exert a gravitational attraction on other objects, the size of which depends on their mass and distance apart, and that the force of gravity on a mass of 1 kg on the Earth’s surface is approximately 10 N.

The distinction between mass and weight will probably not be clear to them, and it is useful to show video clips of weightlessness and of astronauts walking, in a bouncing way with very high slow steps, on the Moon.

Give more advanced students some calculations to do on the weight of different masses in different gravitational environments.

ICT opportunity: Download video clips from the Internet.

The gravitational attraction on the Moon is one-sixth of that on Earth, whereas the gravitational attraction on Jupiter is 300 times that on Earth.

3 hours

What forces can do Give and explain everyday examples of how forces can cause stationary objects to move and can change the direction and speed of an object that is already moving.

Give and explain everyday examples of how forces can cause objects to change shape.

Recall earlier work and identify gaps in understanding Students’ understanding of what forces can do will have emerged in their work on the concept map above. Summarise on the board or OHP what they have told you about what forces can do. If there are gaps in their understanding, address these, preferably with small activities or demonstrations as in the previous topic.

One area where they may well experience difficulties is over the concept of friction, which they met in Grade 5. Have a small activity ready in which students pull, using a forcemeter, a block of wood, perhaps weighted with some masses on top, over a variety of surfaces, including glass, the desktop, carpet and sandpaper. Ask them to tabulate the results and then elicit conclusions to their observations. Draw a diagram showing the pulling force and the frictional force opposing the motion.

Conclude that friction is a force that opposes the motion of a moving body. Ask the class to think of examples of friction and classify them as friction that is useful and friction that is a problem.

If some have noted the difference between static friction and dynamic friction, explain this to them.

Unit 7P.4



Forces cause or change movement Students will recall that forces can cause and change movement. This is very clear in any ball game. Show some video clips of a football or tennis match and use the frame-by-frame setting to look closely at what happens when a force is applied to the ball. Look at examples where the ball is initially stationary (or, in tennis, a serve), noting that in these cases the direction and speed of the ball is determined only by the size and direction of the force. Then look at instances when the ball is already moving when it is hit, particularly when it is hit on the volley. Show that, in these cases, the resulting speed and direction are caused by a combination of the kick or shot and the initial speed and direction of the ball. Introduce the idea of a resultant force. This will be taken further below.

It is important to emphasise that an object travelling with constant velocity has no net force acting on it. If it accelerates or decelerates or changes direction, a force is acting on it. A bicycle travelling at constant velocity, for example, has three forces acting on it, the force due to the rider, the air resistance and the friction between the tyres and the road. These balance each other so that the resultant is zero. This idea should be covered in the next topic, when the idea of a resultant of several forces is developed. Set questions on this to help develop students’ understanding of it. Some examples are given in the assessment section.

ICT opportunity: Frame-by-frame analysis of video clips.

Forces change the shape of objects Ask the class to think of examples where the application of a force changes the shape of an object. List them on the board or OHP. Have a few examples ready to show (e.g. a balloon to squeeze, a rubber band, a photograph of a football being kicked).

Stretch a spring or rubber band In this activity, students will work in groups to investigate the effect of forces on a rubber band or spring. The idea is not, at this stage, to demonstrate Hook’s law, although more advanced students could do this, but to involve students in the planning and execution of an activity that addresses the topic quantitatively and systematically.

Ask each group to stretch the spring incrementally, using hanging masses, and to tabulate the results. Give them clear instructions about what to measure and how to plot a graph of load against extension. They should tabulate the results and plot the graph individually This investigation can be used to assess the ability of students to plot a graph and to draw conclusions from it.

Note that a spring will give a straight line graph when load is plotted against extension but a rubber band will not. Using a spring is therefore more desirable but also more expensive if the spring is stretched to destruction.

Enquiry skills 7.3.2, 7.3.3, 7.4.1



Introduction Place a heavy book on the desk and ask students whether there are any forces acting on it if it is not moving and not changing shape.

Some students will realise that the force of gravity is acting on the book pulling it down. Ask them if there are any other forces acting on it? Choose someone who says ‘no’ and place the book on his or her horizontally outstretched hand. Wait until they are clearly feeling some discomfort and then ask if they have changed their mind.

Introduce the idea of the reaction of the desk on the book, which exactly opposes the force of gravity pulling it down. Draw these two balanced forces on the board or OHP.

As a further illustration, obtain a helium-filled balloon and allow it to float to the ceiling. Discuss the forces acting on it and their origins (recall the work on upthrust in Grade 6). Pull it down from the ceiling and attach some small masses to it exactly sufficient to allow it to float motionless in the air. Ask one student to draw a sketch of it on the board or OHP showing the magnitude and direction of all the forces acting on it. Use this as an opportunity to introduce the convention of the length of the arrow representing the size of the force. In this case, the upthrust and weight arrows must be the same length.

Two unbalanced forces acting on an object Ask students, in groups, to attach two forcemeters to a quite heavy object (a 1 kg mass, say) using string. Two students should pull the object in different, but not opposite, directions and note the force they are exerting. The other students in the group should note the direction of both forces and the direction of movement of the object. They should then draw this arrangement to scale with arrows showing the forces and the direction of the resulting movement.

Reproduce one of these diagrams on the board or OHP. Explain that the effect of the two forces was the equivalent of one force acting in the direction of the movement. Introduce the idea of this resultant force.

Extend this with more advanced students to include the idea of the parallelogram of forces.

Three or more forces acting on an object Give each group a large washer with three lengths of string attached to it and three forcemeters. Tell them to attach one forcemeter to the free end of each piece of string, place the washer in the centre of a sheet of paper and stretch the forcemeters in three different directions so that the washer stays in the centre of the paper. While everything is held still, each forcemeter should be read and one member of the group should draw lines on the paper showing the directions of the string. Ask groups to draw the system to scale with line length representing the size of the forces.

Discuss the results. Ask why the sum of the readings on two of the meters is always greater than the reading on the third. Introduce more advanced students to the idea of the triangle of forces for a system at equilibrium.

2 hours

Many forces acting on an object Know that more than one force is acting on an object that is resting on the floor and know that these forces are balanced so that the object is stationary.

Represent the forces acting on an object diagrammatically, using arrows that show direction and magnitude.

As a consolidation exercise, set a number of questions showing two or more forces acting on an object and ask students to predict the approximate direction and size of the resultant, and whether or not the object is likely to move (see previous topic). Include some requiring numerical answers for more advanced students.



Introduction Place some heavy objects in a corner depression in an otherwise empty polystyrene egg box and close the lid. Place the box near the edge of the desk with the heavy corner away from the edge. Slowly push the box over the edge of the desk. It will not fall as long as the heavy corner is above the desk. Discuss why it does not fall. Lead to the idea of a point in the object in which the mass of an object appears to be concentrated and through which the weight acts.

The centre of gravity of a regular object Challenge the class to find the centre of gravity of a regular object, such as a textbook or a ruler. Some will try to balance it on a finger and will be able to find an approximate place of balance, which will be in the centre of the object.

2 hours

Centre of gravity Know that the centre of gravity of an object is the point through which its mass appears to act.

Know that if the centre of gravity is not above the base of the object, the object will be unstable.

The centre of gravity of an irregular lamina Demonstrate that the centre of gravity of a suspended object is always directly below the point of suspension by hanging up a regular lamina with the centre marked. Show, using a diagram, the turning moments that would exist if this was not so.

Give out some irregular sheets of cardboard and some lengths of cotton and challenge students, in groups, to find the centre of gravity of their sheet. Some groups may need help.

Ask them to check their point by balancing the sheet on a pin. The point of balance should be the one they have found.

Centre of gravity and stability Prepare a plastic soft-drink bottle so that it no longer stands vertically upright when it is empty. This can be done by placing a small round wooden or plastic ring asymmetrically around the bottom so that the empty bottle does not stand vertically. Put the bottle in a sink and ask a student to fill it with water carefully. At some point it will fall over (check this beforehand). Ask the class why it fell over.

Ask students whether they can suggest any applications of our understanding of centre of gravity and stability. Examples include the design of cars (show a video clip of a formula 1 car cornering) and boats. In the case of cars, stress the importance of a low centre of gravity, which should always be above the wheelbase. In the case of boats, stress the importance of the centre of gravity being below the waterline to avoid capsizing.


Assessment


A footballer kicks the ball. Describe two effects that the force he exerts will have on the ball.

Draw a diagram showing the ball moving in the air with an arrow showing the direction of movement. Add two more arrows to show the two forces, weight and air resistance, that act on the ball. Draw the resultant force acting on the ball.

A cyclist travels along a road. Draw a diagram showing the three forces that are acting on the bicycle. Label the force generated by the cyclist A, the friction between the tyres and the road B and the air resistance C.

If the cyclist is travelling with a constant velocity, write an equation showing the relationship between A, B and C.

The diagram shows an empty vase that is held in a tipped position. The arrow W shows the weight of the jar acting from its centre of gravity. If the jar is released, what will happen to it?

The tipped jar is filled with water. Draw a diagram showing the new centre of gravity and the direction its weight now acts. Explain what will happen, and why, when the jar is now released.

Assessment Set up activities that allow children to demonstrate what they have learned in this unit. The activities can be provided informally or formally during and at the end of the unit, or for homework. They can be selected from the teaching activities or can be new experiences. Choose tasks and questions from the examples to incorporate in the activities.

A car is stuck in the sand. The driver tried to pull it free using a rope and exerting a force of 200 N. He could not get it out. He then tied the rope to a tree as shown in the diagram and tried again. This time he pulled the car out.

a. Draw a diagram to show the resultant force on the car.

b. Make an estimate of the size of the resultant force. (More advanced students can draw a diagram to show the size of the resultant force.)

c. Explain why the man was able to exert a greater force this way than the one he exerted with the single rope.

Unit 7P.4

°


GRADE 7: Physical processes

Electrical circuits

About this unit This unit is the fifth of five units on physical processes for Grade 7.





Previous learning To meet the expectations of this unit, students should be familiar with the operation of simple electrical devices such as a torch. They should be able to connect cells to a bulb to complete the circuit such that the bulb lights.

Expectations By the end of the unit, students construct simple series and parallel circuits from circuit diagrams and investigate the current flow in them. They understand why bulbs in parallel are brighter than the same bulbs in series and recognise the implications for household circuits. They know the purpose of safety devices such as fuses and circuit breakers and explain how they work.

Students who progress further gain a qualitative understanding of the concept of electrical resistance. They know that cells and batteries store energy that can be released when the cell is used in a circuit. They know the purpose of the earth lead and can explain how it improves electrical safety.

Resources The main resources needed for this unit are: • circuit boards and accessories sufficient for one board between two or

three students • ammeters • 12 V battery, 5 A fuse wire and circuit breaker, leads • picture illustrating the main do’s and don’ts of mains electricity

Key vocabulary and technical terms Students should understand, use and spell correctly: • circuit, series, parallel • cell, battery • bulb, resistor, rheostat, diode • fuse, circuit breaker

UNIT 7P.5 9 hours



9 hours SUPPORTING STANDARDS CORE STANDARDS Grade 7 standards

EXTENSION STANDARDS

7.20.1 Know that electricity requires a complete circuit to flow. 7.20.2 Represent circuits by circuit diagrams and construct circuits given a circuit

diagram.

7.20.3 Know that reversing the polarity of the cell reverses the current in the circuit.

5.14.1 Construct simple circuits using bulbs, switches and cells, and know that a circuit must be complete and have a source of electrical power in order to work.

7.20.3 Know that current flows around a circuit from the positive to the negative pole of the cell and that in a series circuit it is the same at all points in the circuit but it divides along the branches of a parallel circuit.

9.21.1 Understand the concept of electrical potential difference between two points on a circuit and know that it is measured in volts using a voltmeter.

7.20.4 Know why bulbs in parallel are brighter than the same bulbs in series and recognise the implications for household circuits.

5.14.4 Know that increasing the number of cells in series in a circuit will make bulbs shine brighter but that increasing the number of bulbs in series in the circuit makes them shine less brightly

7.20.5 Understand why adding cells in series will increase the current flowing in a circuit and that adding cells in parallel will not increase the current that flows but will allow the current to flow for a longer time before the cells run down.

9.21.5 Know that electrical components have resistance that impedes the flow of electricity through them and that this is measured in ohms.

7.20.6 Know that batteries are cells connected in series.

5 hours

Electrical circuits

3 hours

Series and parallel circuits

1 hours

Hazards of mains electricity

7.20.7 Be aware of the hazards of mains electricity and explain the purpose of safety devices such as fuses and circuit breakers and how they work.

9.22.6 Be familiar with household ring main circuits, with the common dangers of household electricity, and with the purpose and operation of safety devices such as fuses, circuit breakers and the earth wire.

7.4.6 Select and use electrical components appropriately and successfully solve problems in malfunctioning electrical circuits.

Unit 7P.5


Activities


Simple circuits For this activity, divide the class into small groups of two (preferably) or three students. Each group should have a circuit board with two cells, two bulbs and a switch. Do not introduce the session formally or set any discovery tasks. Allow them to manipulate the equipment for some time. Assist groups with any issue that may be giving problems. Note any groups that are accidentally short-circuiting any cells as this will greatly reduce cell life.

After 15 to 20 minutes, call the class to attention and make a summary on the board of anything they have discovered. This should include, for example: • for a bulb to light a circuit must be complete; • cells must be connected the correct way round if more than one is used; • connecting two bulbs in series results in them being less bright than one bulb in the same

circuit; • bulbs can be connected either way round in the circuit.

The bulbs provided should be of sufficiently high rating to avoid the problem of burning out. All bulbs used in this unit should be identical.



5 hours

Electrical circuits Know that electricity requires a complete circuit to flow.

Represent circuits by circuit diagrams and construct circuits given a circuit diagram.

Know that current flows around a circuit from the positive to the negative pole of the cell and that in a series circuit it is the same at all points in the circuit but it divides along the branches of a parallel circuit.

Select and use electrical components appropriately and successfully solve problems in malfunctioning electrical circuits.

Circuit diagrams Introduce the concept of a circuit diagram and give students a list of common symbols (which they should copy into their exercise books) and ask the groups to set up specific circuits that you write on the board or OHP (or worksheet) and to comment on the brightness of the bulb. Some groups will have difficulty in setting up a circuit from a diagram. Help by asking them to draw the circuit ‘life-size’ on the bench (or on the circuit board) in chalk, place the components on their drawing and join them up with wires. Limit the maximum number of components to two cells and two bulbs at this stage.

Explain to the whole class that the electrical current flows from one pole of the cell around to the other. Explain to them the positive and negative convention and show them which is the positive pole on a simple cell. Show which pole is the positive on the circuit diagram and show the current direction with an arrow.

Set up a mixture of circuits with the bulbs connected in series and in parallel.

Ask students to predict what will happen when each circuit is switched on and then to test their predictions. At least one of the diagrams should be of a circuit that will not work; it could be an incomplete circuit or a circuit with two cells of opposing polarity.

Enquiry skill 7.1.1

Unit 7P.5



Measuring current Show the class how an ammeter is used to measure current. Also show them the symbol for the ammeter. Give each group an ammeter and set the groups a number of tasks by giving them some simple circuits to set up in which they must measure the current at several different points. They should realise that the ammeter tells them current direction as well as magnitude. Ask them to record the results by writing values for current measured next to the ammeter symbol in the circuit. Limit the exercises to series circuits, but the number of bulbs can be increased to three.

Ensure that the class understands the relationship between current and number of bulbs in series. Ensure that they also realise that, in a series circuit, the current is the same at all places in the circuit.

Do not, at this stage, use parallel circuits and avoid using the names series and parallel.


Predicting current Set a simple pencil-and-paper consolidation exercise that requires students to predict the current through different series circuits.

More components Give each group examples of additional components (e.g. rheostats, resistors, buzzers, diodes). Ask them to find out what these components do by connecting them in a circuit with a bulb. Ask them to draw circuits of everything that they set up. Show the symbols for the components used.

Ask the groups what they have found out and summarise this in a table. The diode at this stage could be defined as ‘an electrical one-way-street’, as the concept of resistance is not yet clearly defined.

More advanced students can discuss the idea of resistance to the flow of current by some components. This will be studied again quantitatively in Grade 9.

Introduce different kinds of switch (e.g. bell-push switch, two-way switch). Challenge students to use the two-way switch to simultaneously switch on and off two arms of a parallel circuit.

As a consolidation exercise, draw a number of circuits incorporating a variety of components and ask students to predict what happens when the circuit is connected up. If time allows, they can test their predictions.

Diodes can easily be damaged; limit the number of cells to be used to one and ensure that the diode is always connected in series with a bulb.



Simple series and parallel circuits Introduce the idea of bulbs connected both in series and in parallel. Give examples in the form of circuit diagrams and ask groups to measure the current at places indicated. Ask them to draw all their circuits in their book and to write the current next to each ammeter symbol.

Draw simple conclusions from the class by discussion. These should focus on the brightness of the bulbs compared with the bulb in a circuit with one bulb and one cell and on the current flowing through the bulbs. The effects on bulb brightness of increasing the number of cells in series and on connecting the bulbs in series and in parallel should emerge, and appropriate conclusions should be made about the size of the current in different arms of a circuit.

Make sure students are clear about two important points: • the current passing through a series circuit is determined by the number of bulbs in it; the

more bulbs it has to go through the smaller it is; • the current divides in a parallel circuit and the current passing along each arm of the circuit

will depend on how many bulbs in series there are in that arm of the circuit.

Set another simple pencil-and-paper consolidation exercise that requires students to predict the current through different series circuits and different arms of parallel circuits.

3 hours

Series and parallel circuits Know that current flows around a circuit from the positive to the negative pole of the cell and that in a series circuit it is the same at all points in the circuit but it divides along the branches of a parallel circuit

Know why bulbs in parallel are brighter than the same bulbs in series and recognise the implications for household circuits.

Understand why adding cells in series will increase the current flowing in a circuit and that adding cells in parallel will not increase the current that flows but will allow the current to flow for a longer time before the cells run down.

Know that batteries are cells connected in series.

Cells and batteries As a demonstration, take apart a 1.5 V cell and also a battery, such as a 9 V battery, to show that a battery contains several cells in series. From now on, reserve the word cell for a single cell and battery for a battery of cells in series. Show students a car battery as an example of six cells in series.

Discuss the difference between the ‘use once’ cell and rechargeable cells. Teach more advanced students that electricity is produced as a result of a chemical reaction and that this is reversible in the case of rechargeable cells.

Remind students that cells – particularly rechargeable cells – should not be thrown away after use but should be recycled. The school science department could set up a cell recycling centre.

Also make students aware of the dangers associated with attempts to recharge non-rechargeable cells.

A 1.5 V display cell can be prepared for the class by sawing it longitudinally down the centre to show the different parts. Take care to prevent chemicals getting on your skin as one of them is an oxidising agent.

Electrical energy Although the concept of energy is not formally introduced until Grade 8, it may be mentioned in passing in this topic because students will be familiar with the fact that cells eventually ‘run down’. Explained this in simple energy terms: the cell contains energy (you could call it chemical energy) which is converted into electrical energy which makes the bulb light up.

Draw students’ attention to the fact that, although two bulbs in parallel are brighter than two bulbs in series, they are taking more energy from the cell because the current from the cell is larger, and so the cell will run down more quickly.



1 hour

Hazards of mains electricity Be aware of the hazards of mains electricity and explain the purpose of safety devices such as fuses and circuit breakers and how they work.

Introduction Ask the class what they know about the dangers of mains electricity. As they answer the questions, list the hazards they raise on the board or OHP. It is useful to have available a picture illustrating the main do’s and don’ts of mains electricity; these can be found in many textbooks. If copies of the picture are available, give them out. They will have raised some of the following issues. Any issue that has not been raised should be added to the list. The list should include: • frayed leads; • not poking objects into electrical sockets; • not handling electrical equipment with wet hands or using electrical equipment in a bathroom; • not overloading sockets; • not removing the case of an appliance while it is plugged in; • not running anything except lights from lighting sockets;

Discuss the effect on the body of an electric shock. Ensure that all are aware that if someone receives a shock, the first thing to do is turn off the supply.

Demonstrate the action of a fuse and/or circuit breaker Show students that square pin plugs contain a fuse; crack open one of the fuses to show that it contains a piece of thin wire. Demonstrate the effect on a piece of 5 A fuse wire in a circuit when the circuit is overloaded.

Perform a similar demonstration using a 5 A circuit breaker.

Explain that the rating of the fuse wire and the circuit breaker should be such that it will trip or burn if overloaded but not in normal use.

Show more advanced students, in simple terms, how an earth wire works to ensure that a damaged appliance does not become dangerous.

Safety: Use a 12 V battery as a source, not the mains.


Assessment


The scale shows an ammeter which measures from 0 to 1 ampere. Show where the pointer of the ammeter would be if the current flowing was:

a. 0.6 A;

b. 0.06 A;

c. 0.32 A.


In the circuits shown, all the bulbs and cells are identical. Predict the reading on the ammeters in circuits B to D if the reading on the ammeter in circuit A is 0.2 A.

Unit 7P.5



Noor made an electrical circuit that used three bulbs, A, B and C. She covered the circuit with a card as shown so that the bulbs showed through three holes. The brightness of the bulbs was different. Ibrahim removed each bulb in turn. When he removed bulb A, bulb B went out but bulb C stayed on. When B was removed, C stayed on but A went out. When he removed C, A and B stayed on. Draw the circuit.

Which bulb is the brightest? Explain your answer.

Add switches to the circuit diagram that:

a. turn off all three bulbs;

b. turn off only bulbs A and B.

Design and made a circuit that will:

a. switch on a buzzer when a door is opened;

b. use two two-way switches such that when either switch is switched any way, a bulb will switch on, and then off using either of the switches (this is a how a stairway light with two switches works).

Science scheme of work for the State of Qatar · scheme of work reflects Qatari values and culture...

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