YEAR 8 KO

Breathing &

Respiration

Keywords

Breathing The inflation and deflation of the lungs by the contraction of the diaphragm and intercostal

muscles.

Lung volume Measure of the amount of air breathed in or out.

Respiration Reaction which release energy from glucose.

Gas exchange Process involving gases moving in and out of our blood.

Aerobic respiration Breaking down glucose with oxygen to release energy and producing carbon dioxide and water.

Anaerobic

respiration

Releasing energy from the breakdown of glucose without oxygen, producing lactic acid (in

animals).

Fermentation Yeast anaerobically respiring to produce ethanol and carbon dioxide.

Structure of the Lungs

Trachea - Carries air from the mouth and nose to the lungs.

Bronchi - Two tubes which carry air to the lungs.

Bronchioles - Small tubes in the lung.

Alveoli - Small air sacs found at the end of each bronchiole.

Diaphragm - A sheet of muscle found underneath the lungs.

Respiration

Aerobic respiration in animals:

Glucose + oxygen → carbon dioxide + water

C6H12O6 + 6O2 → 6CO2 + 6H2O

Anaerobic respiration in animals:

Glucose → lactic acid

C6H12O6 → 2C3H6O3

A poisonous waste product called lactic acid is produced, which can be

removed by reacting it with oxygen:

Lactic acid + oxygen → carbon dioxide + water

Anaerobic respiration in yeast (fermentation):

Glucose → Ethanol and carbon dioxide

Gas Exchange

Gas exchange takes place in the

alveoli, the tiny air sacs at the end of

the bronchioles.

1. Oxygen molecules diffuse from the

alveolus into the blood in the

capillary, moving from higher to lower

concentration.

2. Carbon dioxide molecules diffuse

from the blood in the capillary into

the alveolus, moving from higher to

lower concentration.

Root structure showing root hair cell

Keyword Definition

Photosynthesis The chemical reaction by which plants make glucose using

light, carbon dioxide and water

Xylem Tissue that carries water from the roots to the leaves

Phloem Tissue that carries dissolved sugars around the plant

Transpiration The loss of water vapour through pores in the leaf

Transpiration stream Movement of water through roots and xylem to the leaves

Reactants Chemicals required for a chemical reaction

Product Chemicals produced in a chemical reaction

Part of Plant Adaptations

Roots Root hair cells to increase surface area for

absorption of water

Stem Tube like xylem to carry water

Tube like phloem to carry dissolved sugars

Leaf - Epidermis/cuticle Reduces water loss and prevents the entry of

pathogens

Leaf - Palisade mesophyll Regular shaped cells with large numbers of

chloroplasts to increase the rate of photosynthesis

Leaf - Spongy mesophyll Provides air gaps to allow gas exchange (oxygen

out, carbon dioxide in)

Leaf - Guard cells Allow pores (stoma) to be opened and closed to

control water loss

Factors affecting the rate of

photosynthesis:

Light intensity

Colour of light

Carbon dioxide concentration

Availability of water

Temperature

Number and size of leaves

How do plants use glucose?

Respiration

Production of large molecules:

● Starch

● Proteins

● Oils and fats

Roles of roots

● Stability of plant

● Absorb water

● Absorb minerals

Cross section of a leaf:

Water + carbon dioxide → oxygen + glucoselight

chlorophyll

Year 8

Photosynthesis

SoundKeywords

Vibration A back and forth repeating motion.

Vacuum A space with no particles of matter in it.

Oscilloscope Device for viewing patterns of sound

waves that have been turned into

electrical current.

Absorption When energy is transferred from sound to

a material.

Echo Reflection of sound waves from a surface

back to the listener.

Wave Characteristics

Wavelength

The distance from a point on one wave to the same

point on the next wave.

Measured in metres and has the symbol λ (Greek letter

lambda).

A shorter wavelength = higher frequency.

Frequency

The number of waves passing a point every second

and is measured in hertz (Hz).

A higher frequency means a high pitch.

Amplitude

The height of the wave from the centre line to a peak

or trough.

Measured in metres.

The more energy a wave has the bigger the amplitude

and the louder the sound.

Waves

Waves can travel in two ways:

1. Longitudinal waves travel in straight lines - where the

direction of vibration is the same as that of the wave.

2. Transverse waves move at right angles to the

direction of the wave.

Sound waves are longitudinal waves. They involve particles

and have areas of compression and rarefaction.

The Ear & Hearing

1. Your outer ear channels sound waves into your ear.

2. The sound waves travel along the auditory canal.

3. The ear-drum vibrates when a sound hits it.

4. The vibrating ear-drum makes the little bones in your ear

vibrate.

5. The vibrations pass along the auditory nerve your brain.

6. Your brain sorts the messages and you hear the sound.

Hearing loss could be caused by:

Wax blocking the ear

Loud noises tearing eardrum

Ear infection

Small bones in the ear can get stuck together

Loud noises can damage the cochlea

Light

Keywords

Normal line A line drawn at right angles to the surface where the ray hits. Angles are

measured from this line.

Absorption Light is transferred to a material and is not reflected or transmitted.

Transmitted Light that passes through an object is transmitted.

Scattering When light bounces off an object in all directions.

Transparent An object that allows light through without scattering.

Translucent An object that allows light through with scattering.

Opaque An object that allows no light through.

Reflection

When light is reflected it

bounces off of something.

We use ray diagrams to

draw reflections.

To help us with our ray

diagram, we can draw a

line 90o to the reflective

material.

This line is called the normal.

Angle of incidence = angle of reflection.

Calculating wave speed

Speed = wavelength x frequency

(m/s/) (m) (Hz)

Symbol equation: v = f x λ

Equation rearranged:

Wavelength = Speed/frequency

Frequency = Speed/wavelength

Refraction

Waves are refracted when they change speed.

When waves slow down they bend towards the normal line. This happens when light travels

from air to glass.

When waves speeds up they bend away from the normal line. This happens when light

travels from glass to air.

The angle of refraction is less than the angle of incidence.

InheritanceKeywords

Inherited

characteristics

Features that are passed from parents to offspring.

Allele The form of a gene (e.g. an allele for the hair colour gene might be blonde, or

brown etc).

Dominant The allele that will show up. (Written as a CAPITAL letter eg B for brown)

Recessive The allele that does not show up if there’s a dominant allele too. (Written as a

lowercase letter eg b for blonde)

Genotype Genetic makeup of an individual for a particular characteristic eg Dd

Phenotype Physical appearance eg dimples or no dimples, black fur or brown fur.

Genetics

Our genetic information is stored inside the nucleus of all cells.

DNA consists of two long strands wound together in a double helix structure.

In our cells, long DNA strands form structures called chromosomes.

A gene is a specific section of a chromosome (eg. the gene for eye colour).

Humans get 23 chromosomes from their Father (sperm) and 23 chromosomes from

their Mother (egg), which combine to make an embryo with 23 pairs of chromosomes.Variation

Variation is the differences in characteristics

between individual organisms.

There are 2 types of variation:

1. Genetic Variation: Genes control the

development of characteristics. Eg, eye colour.

2. Environmental Variation: Characteristics may

be changed by the environment. Eg,

personality.

Genetic Modification

Genetic modification is the modification of

an organism's characteristics by

manipulating its genetic material.

Examples:

- Modifying bacteria to produce insulin for

human use.

- Modifying rice to contain more vitamin A to

reduce deficiencies in developing countries.

- Modifying vegetables to have a longer

shelf life.

Evolution

Keywords

Adaptations Features that help an organism survive in a particular environment.

Natural selection Species change over time in response to environmental changes and competition.

Extinct When no more individuals of a species remain.

Biodiversity The variety of living things.

Competition When organisms struggle against each other to get the same resource.

Evolution Theory that the organisms living today descended from species that existed in the

past.

Natural selection

1. Each species naturally shows variation.

2. There is intraspecific competition for resources (food, water, land, mates, etc).

3. The individuals who are better adapted to the environment are better competitors.

4. These individuals are more likely to survive and reproduce.

5. The advantageous genes are passed onto their offspring, which makes them better

competitors too.

6. Poor competitors die out.

Fossils

1. Death: Having died, the organism slowly sinks to the sea floor. After a few weeks, the flesh

decays, leaving only the hard bones or shells behind.

2. Deposition: The shell or bones gradually become covered with layers of silt and sand, which

provide a shield, protecting it from damage. After a few hundred years the shell or bones are several

feet beneath the surface.

3. Mineralisation: Thousands of years pass. In the wet environment the shell or bones are exposed

to, minerals pass through and react with them.

4. A fossil is formed: After millions of years, the original shell or bone is completely replaced by the

minerals and what remains is a rock-like copy of the original shell. The fossil has the same shape as

the original object, but is actually rock.

Adaptations for hot climates Adaptations for cold climates

Little fur

Little fat

Large surface area to volume ratio

Thick fur

Lots of fat/blubber

Small surface area to volume ratio

Darwin’s theory of evolution

Darwin noticed slight differences between similar species and proposed the theory of

evolution:

“All species of living things alive today have evolved from the first simple life forms that

first developed three billion years ago.”

Evidence: fossil record, selective breeding of animals and plants, observations of

species, DNA analysis

SpeedKeywords

Speed How much distance is covered in how much time.

Average speed The overall distance travelled divided by overall time for a journey.

Relative motion Different observers judge speeds differently if they are in motion too, so an

object’s speed is relative to the observer’s speed.

Acceleration How quickly speed increases or decreases.

Distance-time graphs

A distance-time graph shows how an object moves in a given period of time.

We can find out:

- How far the object travelled from its starting point.

- How long it took to make the journey.

- If the speed was constant or if the speed changed.

- When the object was stationary.

If the graph CURVES UPWARDS, this means the object is accelerating.

If the graph line is STRAIGHT, the object is going at a CONSTANT speed.

If the slope is LESS STEEP, this shows the object is travelling at a slower constant

speed.

If the graph line is HORIZONTAL, the object is stationary.

Calculating speed

Speed = Distance

Time

The unit for speed depends on the units for distance and time given in the question. For example, if

distance is in km and time is in seconds, then the unit for speed is km per second.

Worked example:

A boy takes 2 hours to travel from his home to grandparents, a distance of 10 km. Calculate his

average speed in km/h.

Speed = Distance = 10 km = 5 km/h

Time 2 h

Calculating relative motion

1. For objects moving in the SAME direction:

Calculate the difference between the fastest and slowest speeds.

(i.e. Fastest speed – slowest speed)

2. For objects moving in the OPPOSITE direction:

Add the two speeds together

Pressure

Keywords

Fluid A substance with no fixed shape, a gas or a liquid.

Pressure The ratio of force to surface area, in N/m2 and how it causes stresses in

solids.

Upthrust The upward force that a liquid or gas exerts on a body floating in it.

Atmospheric

pressure

The pressure caused by the weight of the air above a surface.

Area The area of a shape is a measure of the two dimensional space that it covers.

A shape’s area can be measured in square centimeters, square metres or

square kilometres

Hydraulic systems

Hydraulic systems use the principle that pressure is transmitted throughout a liquid.

They are used to transfer movement from one part of a machine to another without linking the

parts mechanically.

All hydraulic systems use two pistons linked via a pipe carrying a special oil called hydraulic fluid.

The piston where the force is applied is called the master piston, and the piston where the force

is transferred is called the slave piston.

Calculating pressure

Pressure (Pa) = Force (N)

Area (m2)

If the force is in N and the area is in m2, the unit for pressure is Pa.

However, if the force is in N and the area is in cm2, the unit for pressure is N/cm2.

Worked example:

An elephant that weighs 40,000N stands on one leg during a circus performance. The

area on the bottom of the elephant’s foot is 0.4m².

Pressure = Force = 40,000 N = 100,000 Pa

Area 0.4 cm2

Floating and sinking

An object will float if weight is equal to the upthrust.

How to work out if an object will sink or float:

1. Measure the mass of an object.

2: Work out the weight (weight = mass x gravitational field strength (10))

3. Submerge the object in water and work out how much water was displaced. (water level

in the cylinder after - water level before)

4. Work out the mass of displaced water. Water has a mass of 0.001kg per 1cm3. So your

answer will be:

Mass of water displaced (step 3) x 0.001 = ______

5. Work out the weight of water displaced (answer to step 4 x 10).

6. The weight of the displaced water is equal to the upthrust, You can now compare the

weight of the object and the upthrust to judge whether it will float or sink.

The Periodic Table

Keywords

Periodic table Shows all the elements arranged in rows and columns.

Groups Columns of the periodic table that group elements with similar properties

together.

Periods Rows of the periodic table that arranges atoms by their proton number.

Element A substance made up of one type of atom.

Compound A substance that consists of two or more elements chemically bonded

together.

Conservation of

mass

The rearrangement of atoms during chemical reactions results in the overall

mass being unchanged.

The arrangement of the periodic table

All of the different elements are arranged in a chart called the periodic table.

The columns are called groups, and the rows are called periods.

Elements to the left of the staircase line are metals and the elements to the right of this

line are non-metals.

Group 1 metals are called the alkali metals.

Group 7 elements are called the halogens.

Group 0 elements are called the noble gases.

The elements in between group 2 and 3 are called the transition elements.

Naming compounds

When atoms combine, their names often change slightly.

Rules to help you name compounds:

1. Use prefixes - mono, di, tri.

For example, SO is sulphur monoxide. SO2 is sulphur dioxide. SO3 is

sulphur trioxide.

2. When a metal and non-metal combine, change the non-metal to

‘ide’.

For example: NaCl is sodium chloride. MgO is magnesium oxide.

3. When 3 or more different elements combine and one is oxygen,

change the end to ‘ate’.

For example, CuSO4 is copper sulphate. CaCO3 is calcium carbonate.

KNO3 is potassium nitrate.

The structure of the atom

Subatomic particle Relative charge Relative mass

Proton +1 1

Neutron 0 1

Electron -1 Almost 0

Metals and Non-Metals

Keywords

Metals Shiny, good conductors of electricity and heat, malleable and

ductile, and usually solid at room temperature.

Non-metals Dull, poor conductors of electricity and heat, brittle and usually

solid or gaseous at room temperature.

Malleable Can be hammered or pressed into shape without breaking or

cracking.

Brittle Easily broken or shattered.

Conductor A material that transmits heat or electricity.

Rust The corrosion of iron.

Metal + Water

Metal + water → Metal hydroxide + hydrogen

Example:

Lithium + water → Lithium hydroxide + hydrogen

2Li + 2H2O → 2LiOH + H2

Rusting

Rusting is a term used to describe the corrosion, or wearing down, of the metal iron

Iron + oxygen → Iron oxide

4Fe + 3O2 → 2Fe2O3

Oxygen and water are necessary for rusting to occur.

Common Salts

Hydrochloric acid (HCl) → chlorides (-Cl)

Sulphuric acid (H2SO4) → sulphates (-SO4)

Nitric acid (HNO3) → nitrates (-NO3)

Metal + Acid

Metal + acid → Metal salt + hydrogen

Example:

Magnesium + hydrochloric acid → Magnesium chloride + hydrogen

Mg + 2HCl → MgCl2 + H2

Metal + Oxygen

Metal + oxygen → Metal oxide

Example:

Copper + oxygen → Copper oxide

2Cu + O2 → 2CuO

Metal Carbonate + Acid

Metal carbonate + acid → Metal salt + water + carbon dioxide

Example:

Zinc carbonate + sulphuric acid → Zinc sulphate + water + carbon dioxide

ZnCO3 + H2SO4 → ZnSO4 + H2O + CO2

Y8 - Earth’s Resources

Keywords

Natural

resources

Materials from the Earth which act as raw materials for making a

variety of products.

Mineral Naturally occurring metal or metal compound.

Ore Naturally occurring rock containing sufficient minerals for extraction.

Extraction Separation of a metal from a metal compound.

Recycling Processing a material so that it can be used again.

Electrolysis Using electricity to split up a compound into its elements.

Displacement Reactions

Some metals are more reactive than others. This is displayed in the reactivity series (on the left

hand side).

A displacement reaction is where a more reactive metal takes the place of a less reactive metal in a

compound.

Example:

Copper + silver nitrate → copper nitrate + silver

Copper is more reactive than silver, so the copper has ‘stolen’ the nitrate from the silver - therefore

silver has been displaced.

Extracting Metals

Metals can be extracted from their ores using different methods, depending on their reactivity.

1. Very unreactive metals (the metals less reactive than hydrogen) occur native and do not need extracting.

1. Metals between carbon and hydrogen on the reactivity series can be extracting with a displacement reaction using

carbon. For example: Lead oxide + carbon → Lead + carbon dioxide. Carbon is more reactive than copper, so lead

is displaced.

1. Metals that are more reactive than carbon can be extracted using electrolysis.

Y8 - Climate

Keywords

Global warming The gradual increase in surface temperature of the Earth.

Fossil fuels Remains of dead organisms that are burned as fuels, releasing carbon

dioxide.

Carbon sink Areas of vegetation, the ocean or the soil, which absorb and store carbon.

Greenhouse effect When energy from the sun is transferred to the thermal energy store of

gases in Earth’s atmosphere.

Processes involved in the carbon cycle

1. Photosynthesis:

Green plants and algae remove CO2 from the atmosphere.

Carbon dioxide + water → glucose + oxygen

6CO2 + 6H20 → C6H12O6 + 6O2

2. Respiration:

Respiration causes carbon to be returned to the environment.

Glucose + oxygen → carbon dioxide + water

C6H12O6 + 6O2→ 6CO2 + 6H2O

3. Combustion:

When we burn fossil fuels the carbon within them combines with oxygen to produce

CO2. In this way carbon is returned to the environment.

4. Decay:

The dead organisms are eaten by decomposers and the carbon is returned to the

atmosphere as carbon dioxide.

Gases in our atmosphere

Nitrogen makes up most of our atmosphere.

Currently carbon dioxide levels are about 0.04%.

Methane and carbon dioxide are greenhouse gases.

The greenhouse effect

1. Heat from the Sun enters the earth’s atmosphere and warms the surface of the planet.

2. The earth’s surface becomes warm and radiates heat back out.

3. Some of this heat is absorbed by greenhouse gases. These gases then radiate the heat back towards earth.

4. The earth becomes warmer as a result.

Keywords

Enzyme A biological catalyst

Substrate Molecule(s) acted on by an enzyme

Active Site The site on enzymes where the substrate binds

Denature Change the shape of the active site

Carbohydrates The body’s main source of energy. 2 types: simple (sugars) and complex

(starch).

Lipids Fats and oils. A source of energy.

Protein Nutrient your body uses to build new tissue for growth and repair.

Stomach Where food is mixed with acidic juices and churned

Small intestine Where digestion is completed and nutrients are absorbed by the blood.

Large intestine Where water is absorbed and faeces are formed.

Molecule for

testing

Food test Positive result Negative result

Protein Biuret solution Purple Stays blue

Lipids Sudan III stain Red oil layer at

the top

No layers form

Starch Iodine Blue / black Stays orange

Simple sugars

(glucose)

Benedict’s solution &

heat

Red Stays blue

Enzymes

Enzymes break long food molecules into smaller particles ready for absorption. Without enzymes, the long food molecules

would never be able to pass through the intestine.

Enzymes are a specific shape - complementary to their substrate (the molecule they are breaking down). The enzyme has

an ‘active site’ where it binds onto the substrate.

Digestion

WorkKeywords

Work The transfer of energy when a force moves an object, in joules.

Lever A type of machine which is a rigid bar that pivots about a point.

Input force The force you apply to a machine.

Output force The force that is applied to the object moved by the machine.

Displacement The distance an object moves from its original position.

Deformation When an elastic object is stretched or squashed, which requires work.

Moments

A turning force is called a moment.

We can work out the moment by using this formula:

M = F x r

M = Moment (Nm)

F = Force (N)

r = Perpendicular distance (m)

Worked example: This seesaw is balanced. Calculate force

A

Anticlockwise moment = 50 x 1 = 50Nm

For the seesaw to balance, the anticlockwise and clockwise

moments must be equal.

Force A = 50 / 0.5 = 100N

Mechanical Work

Energy can be transferred from store to store

by forces moving.

When this happens we say that mechanical

work is done.

We can work out how much work has been

done by using this formula:

W = Fs

W = Work done (J) - This is also the amount of

energy transferred.

F = Forces applied (N)

S = Displacement of force (m) - This is the

distance the force has moved.

Remember: Weight (N) = mass (kg) x

gravitational field strength.

1m

50N

50cm

A

Levers

Levers are simple machines that allow us to multiply the force applied.

The longer the lever, the greater the moment created for the same

amount of force applied.

A lever can be used to lift heavy objects.

The weight of the object is called the load.

The force the person applies is called the effort.

The point about which the lever turn is called the pivot or the fulcrum.

Heating & CoolingKeywords

Thermal conductor Material that allows heat to move quickly through it.

Thermal insulator Material that only allows heat to travel slowly through it.

Temperature A measure of the motion and energy of the particles.

Thermal energy The quantity of energy stored in a substance due to the vibration of its particles.

Conduction Transfer of thermal energy by the vibration of particles.

Convection Transfer of thermal energy when particles in a heated fluid rise.

Radiation Transfer of thermal energy as a wave.

Radiation

Thermal energy is transferred by infrared (thermal) radiation.

It travels in waves just like light. Therefore it does not require particles.

All objects emit and absorb radiation to some extent.

The hotter the object, the more radiation it emits.

Also, the darker the object, the more radiation is absorbs and emits.

Conduction

This method of energy transfer occurs in

solids.

All solids are made of particles in a rigid

structure.

As you heat up a solid these particles gain

kinetic energy and vibrate more.

This means more particles bump into each

other, causing the energy to pass through the

solid.

Convection

This method of energy transfer occurs in fluids

(liquids and gases).

When the particles are heated they gain kinetic

energy and move faster.

This means they crash into each other more often

and with greater force.

This makes the fluid expand and become less

dense.

The hot fluid is displaced (pushed out of the way)

by more dense cold fluid.

Reducing energy loss

An insulator is a material that does not transfer heat well.

Insulators in homes slow down the transfer of heat from the warmer internal

rooms the cooler outside.

The way insulators work is by preventing conduction, convection and

radiation.

Examples of insulation in houses:

Loft insulation

Cavity wall insulation

Aluminium foil behind a radiator

Double glazing

Chemical Energy

Keywords

Catalysts Substances that speed up chemical

reactions but are unchanged at the end.

Exothermic

reaction

One in which energy is given out, usually as

heat or light.

Endothermic

reaction

One in which energy is taken in, usually as

heat.

Chemical bond Force that holds atoms together in

molecules.

Activation energy The energy required to start a chemical

reaction (break bonds).

Catalysts

Catalysts never produce more product – they just produce the

same amount more quickly.

Catalysts work by providing an alternative pathway for the

reaction with a lower activation energy.

Energy in chemical reactions

In order for a reaction to occur, bonds in the reactant molecules must be broken, atoms then rearrange, and bonds are

remade to form the products.

In order for reactant bonds to be broken, thermal energy must be supplied. This is called the activation energy. Breaking

bonds therefore requires energy (endothermic).

When bonds are made, thermal energy is released (exothermic).

Exothermic reactions Endothermic reactions

Exothermic reactions release energy as heat during a

reaction.

This can be seen as a rise in temperature as the reaction

thermal energy to its surroundings.

This means that the energy of the products will be lower

than the energy of the reactants.

Endothermic reactions absorb thermal energy during a

reaction.

This can be seen as a drop in temperature as the

reaction absorbs thermal energy from its surroundings.

This means the energy of the products will be higher than

the energy of the reactants.

reaction (time)

en

erg

y

(kJ)

Ea with

catalyst

Ea

without

catalyst

Magnetic field around a bar magnetKeyword Definition

magnet an object that creates a magnetic field around itself

ferromagnetic material a material that experiences a magnetic force when

placed in a magnetic field.

magnetic force a non-contact force that acts of a magnetic material

or a magnet placed in a magnetic field

magnetic field the space around a magnet or a current-carrying

wire

magnetic field line line in a magnetic field along which a magnetic

compass points - also called a line of force

solenoid a long coil of wire that produces a magnetic

field in and around the coil when there is a

current in the coil

electromagnet an insulated wire wrapped round an iron bar

that becomes magnetic when there is a

current in the wire

pole position on a magnet where the magnetic

field is strongest

Increasing the strength of an electromagnet

Improvement Reason it works

Increase the number of coils Increases the length of the magnetic field

producing wire

Increase the current Makes each mm of wire produce a bigger

magnetic field

Parts of an electromagnet

Solenoid Carries the current

Core Focuses the magnetic field

Current Creates the magnetic field

Magnetic materials

Iron

Cobalt

Nickel

Year 8

Magnetism

Field lines - things to remember

● They never cross

● The arrows point from the north pole to the

south pole

● The points where they touch the magnet

are the poles

● Where they are closer together the

magnetic field is stronger

Electromagnet construction