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Prior knowledge

What is a chemical change?

Chemical change – Introduction Chemical changes occur when objects or substances are changed or altered. In a chemical change, particles of the original materials collide with one another. Some chemical reactions (called exothermic reactions) give out heat and may become hot enough to cause certain chemicals to also undergo a change in state. For example, in the case of reactiuons in water-based solutions, bubbles may not necessarily be newly produced gas but instead water vapor. Chemical change is a change which is usually irreversible. Examples of chemical changes:

Burning

Decomposition

Neutralisation (Reacting an acid with a base, resulting in water and a salt)

Photosynthesis – a process in which carbon dioxide and water are changed into sugars by plants

Cracking heavy hydrocarbons to create lighter hydrocarbons (part of the process of refining oil)

Cooking examples: cake, pancakes, and eggs/bacon

Oxidation examples: rust or tarnishing

Ripening examples: bananas, tomatoes or potatoes

How can you tell whether a change is a chemical change? Colour As in the case of autumn leaves, a change in colour is a clue to indicate a chemical change. When you cut an apple open, it starts to turn brown very quickly and different varieties go brown quicker than others. This is because a chemical change occurs when food spoils. Energy Another sign of a chemical change is the release or gain of energy by an object. Many substances absorb energy to undergo a chemical change. Energy is absorbed during the chemical change involved in cooking, like baking a cake. Odour It only takes one experience with a rotten egg to learn that they smell different from fresh eggs. When eggs and food spoil, they undergo a chemical change. The change in odour is the clue to the chemical change. Gases or solids The formation of a gas is another clue to chemical changes. The bubbles of gas that form when an antacid tablet is dropped into water, is an example of a chemical change. Another clue that a chemical change has occurred is the formation of a solid. A solid that separates out of solution during a chemical change is called a precipitate.

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Chemical Reactions Chemical Changes are also called Chemical Reactions. Chemical reactions involve combining different substances. The chemical reaction produces a new substance with new and different physical and chemical properties. Matter is never destroyed or created in chemical reactions. The particles of one substance are rearranged to form a new substance. The same number of atoms that exist before the reaction, exist after the reaction.

Skills focus

Observing and measuring Observation is a really important skill for the scientist. The ability to see what is really happening rather than seeing what you expect to see can be difficult. It’s a good idea to give pupils observation exercises to help them to improve this skill. A good example of an observation exercise is to get them to describe what happens when a match is struck. The first time they see it, they will see the flare of the flame as it is struck, the yellow flame and the match turns to black. If you repeat it, asking them to observe every little detail including sounds and smells, the list they come up with is enormous. Pupils should be able to choose and use simple scientific equipment and materials appropriately and take action to the control risks involved in their use. They need to make systematic observations and accurate measurements using appropriate equipment, including the use of ICT for data logging. In their investigations, pupils should check their observations and measurements by repeating them where appropriate to ensure that they are reliable.

Recording data Pupils should demonstrate their ability to use a wide range of methods, including diagrams, drawings, tables, bar charts, photographs, video clips, voice recordings, line graphs and ICT, to communicate data in an appropriate and systematic manner. Pupils will need explicit skill teaching in order to construct tables, charts and graphs well. They also need practise in choosing the most appropriate method to show their results to analyse and evaluate their evidence. The way data is recorded often depends on the type of data. Measurements are often tabulated before they are put on a graph, pie chart or bar-chart. A bar chart or pie chart is used to show categoric and discrete variables. Continuous variable are show continuous variable Observations which are made can be recorded by photograph, picture or diagram. Events may be recorded using video or sound recording. (For more examples, see the data support sheet, on the website).

Lessons are designed to be flexible, and can be organised to suit your class and timetable. Our suggested plan is to spend one lesson delivering the theory and demonstration. The website has lesson plans and video demonstrations to serve as reminders. Time can then also be spent on the skills focus, i.e. planning, collecting data or interpreting data. Children can discuss predictions, questions that could be tested, variables and possible outcomes. The following week time can be taken to revisit the scientific knowledge and children have the opportunity to plan their own investigation. There is then time to work in pairs to carry out the experiment and evaluate their findings and observations at the end of the lesson.

Each lesson plan has homework suggestions and links to further studies.

Differentiation is not stated by year groups as classes vary from year to year, cohort to cohort and school to school. We state our aims for most children and then for some. This means that every demonstration and investigation has been chosen because any KS2 child can access it at some level. The level of understanding, language used, ability to relate concepts and investigate are the skills which develop as the child learns.

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Changing Form

Lesson Objectives

Choose from: Understand that chemical reactions cause a change. Know that a chemical change is often an irreversible change. Carry out an investigation that will produce valid data.

Essential Knowledge/ Science Explained - for teachers

1. Different salts produce different coloured flames (fireworks are a typical example). In this case the boric acid burns with a green flame. Lithium salts burn with a red flame, barium salts with pale green flame and calcium salts with a brick red flame. Other salt produce different colours.

2. Hydrogel is an interesting polymer as well as an example of a smart material. Hydrogels are smart materials because their molecules change shape when there is a change in their environment – in this case, the change in the concentration of ions. Hydrogels are polymers that can retain many times their own weight in water. The polymer molecules have sites along their length that attract and trap water molecules. Trapping water molecules remove them from the solution making the solution more concentrated and more viscous (thicker). The polymer is in equilibrium with the water around it, but that equilibrium can be disturbed in a number of ways: Adding salt prevents the sites on the polymer molecules that attract and trap water molecules and so the hydrogel gives up the trapped water, and the solution becomes less viscous. Different types of hydrogel can be made that are sensitive to different conditions such as pH, temperatures and ionic concentrations. The hydrogels in this practical activity are sensitive to salt concentration, but are not affected much by changes to pH. However, they do lend themselves very well to a range of investigative practical work. For example, their volume in different amounts of water or in different salt concentrations can be measured. More information on hydrogels can be found using the link. http://www.gcsescience.com/o70.htm

Common Misconceptions

1. Particles can change form or shape. 2. Molecules are indivisible. 3. Molecules of solids are bigger than those of liquids or gases. 4. The space between molecules contains air. 5. Solids, liquids and gases are ‘different’ substances. 6. Chemical reactions are simple mixing of substances. 7. Children often associate gases with the use and function of objects, like footballs and tyres

Termly Scientific Skills Development Focus: Recording and Analysis of Scientific Data and Observations

Collecting and presenting scientific observations in a way that can be analysed. Creating graphs and charts of the data Analysing data the data obtained from the experiment and determining whether or not it proves or disproves the

prediction.

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Opportunities should be given throughout the lesson for children to use and develop their knowledge of planning investigations, through questioning and discussions on questions to investigate, making predictions and suggesting dependent and independent variables.

Cross curricular links

Literacy The green fire could be used as a stimulus for creative writing – poetry.eg. Green is

the colour of… or personification, eg. The fingers of the flame grasped… Begin a science glossary for the class/younger children. Use the green flame demo as a stimulus for adjectives/adverbs or

synonyms/antonyms. Write an instructional text for another class to use to carry out the nappy

investigation.

Numeracy Use tables and graphs to record data collected from the nappy investigation. Calculate averages from other children’s data. Find patterns/is there a ratio between the amounts of water added to the

hydrogel before it becomes saturated? Lots of opportunities for measuring capacity during the investigations.

Other subjects Green fire may inspire some artwork around mythical beasts/fantasy creatures.

Video of Japanese artists drawing dragons in a single stroke - http://www.businessinsider.com/kousyuuya-studios-dragon-art-2014-8?IR=T

New inventions. Watch the video to see how has used hydrogels to solve his problem. http://www.abc.net.au/tv/newinventors/txt/s2494979.htm What problems are there in class and what could children invent to solve them? Giving out books, collecting pencil sharpening’s, lost pens are all common classroom issues.

Preparation

Organise practical and delivery and set up of equipment in classroom.

You may require extra help in the classroom such as a teaching assistant as there is a lot to get through. Suggested Lesson Organisation

Set up and show the demonstration, then explain and introduce the investigations they are to be involved in.

Get the pupils into pairs and get each pair to collect the apparatus and chemicals they will need to carry out the investigation.

It is probably best for pupils to do the hair gel experiment first as that is quite quick and easy to do.

Prior Discussion What is a chemical change? Engage children in a discussion of what they can recall from the Particle Theory and Energy units. List some of the changes that may occur when a chemical reaction has taken place.

Heat Colour Smell Size Change of state

Can children give examples for each one? Or examples from the real world, for example in cooking.

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Teacher Demonstration Demonstration - Green fire See http://chemistry.about.com/od/funfireprojects/a/greenfire.htm Apparatus and chemicals Health & Safety: The teacher must wear eye protection. This may need to be performed outside if there are smoke alarms in the room. If performing inside use the safety screen. For one demonstration, the teacher will need:

Safety glasses

Boric acid

Spatula

Methanol (methyl alcohol)

Heatproof mat

Tin lid

Matches

Safety screen Procedure

Discuss with the class what may happen when you add a powder to a liquid. They may suggest it dissolves, it sinks etc. This can lead to a discussion on whether a new material is made or it is a reversible change.

Take a couple of spatulas of the boric acid and place them in a beaker. Stir with 20 ml of methanol and then pour half into the tin lid.

Most of the boric acid will dissolve but there will be some left in the bottom. This won’t matter as it won’t affect the experiment.

Place the tin lid on the heatproof mat and place the safety screen in front. The children should stand about a metre away from the front of it.

Light the methanol with a match and behold! Green fire!

This is a quick and easy experiment that produces an exciting result. The residue left in the tin lid can be flushed down the sink once the methanol has completely burned off.

Possible Questions/ Suggestions for discussion There is a practical that they will get involved with at high school, if they choose to take chemistry, called ‘Flame Tests’ and that will go into more detail regarding what colour flames are produced when different salts are burned. However in the meantime check out the link below for the full list of salts and the colours they give. http://en.wikipedia.org/wiki/Flame_test Have children seen this anywhere before? It is using mixtures of these salts in the manufacture of fireworks that create the spectacular colours. Magnesium metal burns with a brilliant white light which you get in a sparkler and it is a major component in all fireworks.

Children’s Investigation Hydrogels: Nappies and Hair gels. In this activity students investigate hydrogels: polymeric smart materials. They are found in many commonly available products including disposable nappies and cheap hair gel. http://www.practicalchemistry.org/experiments/experiments-with-hydrogels-hair-gel-and-disposable-nappies,143,EX.html Apparatus and chemicals Health & safety – Safety glasses must be worn by all pupils and teacher throughout. Safety gloves should be worn for man-handling the nappies.

Each group will need:

100 ml measuring cylinder

800 ml tri-pour beaker

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Plastic stirrer

1 nappy

Plastic bowl/tray

Sodium chloride (salt)

Plastic spoon

Water

Petri dish

Hair gel

Paper towels

Safety glasses

Disposable gloves Procedure - Disposable nappy 1. Cut the middle section out of the nappy – the thicker piece that is designed to absorb the urine. Discard the other

piece. 2. Make sure the bowl is completely dry - wipe it with a paper towel if necessary. Any moisture in the tub stops the

experiment from working properly. 3. Put the centre piece of the nappy into the bowl and gently take it apart. Small white grains should start coming away

and this is what you are trying to collect. Keep gently pulling the nappy apart until you have collected as many of the grains as you can. Do not do this roughly or you will lose your product and put a lot of dust and fluff into the air. Avoid breathing in any of the dust which is sodium polyacrylate (Low hazard but eye irritant).

4. Remove and dispose of all the fluff and other parts of the nappy, keeping the grains in the bottom of the bowl. They are heavier and fall to the bottom, which makes it easier to separate them out.

5. Estimate the volume of the grains. 6. Pour them into the large beaker and add about 100 ml of water. Stir. Keep adding water until no more can be

absorbed and stir between each addition. Estimate the final volume of the hydrogel 7. Add a dessertspoonful of salt and stir. Procedure - Hair gel

Put a blob of hair gel onto the petri dish lid. (A large spatula full is fine).

Gently sprinkle a spatula full of salt, over the hair gel. Observe what happens.

Possible Questions/ Suggestions for discussion Students should make detailed notes on their experiments, using recording sheets as necessary, noting changes in volume, colour and any other observations. Some expected observations could include: Hair gel The hair gel shrinks in size very quickly when the salt is added. After a couple of minutes all that is left is some liquid in the petri dish. Disposable nappy About 10 ml of hydrogel can be extracted from the nappy core. (Exactly how much depends on the make and the size of the nappy.) The hydrogel swells up extremely quickly. It absorbs about 500 ml of distilled water giving a very viscous mixture. When salt is added, the viscosity immediately reduces and the mixture is easier to stir. The hydrogel releases the water and settles on the bottom of the beaker.

Learning Outcomes All children should

Practise making predictions and controlling variables. Be able to carry out an investigation which produces reliable data. Record data in a novel way. Approach practical work in a safe and appropriate manner. Know why not all flames are orange and the colour of the flame is affected

by the chemicals which are burning. Name some chemical changes.

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Some children could Practise independently identifying a variable to test in an experiment. Realise there are often problems with investigations and scientists need to

minimize these. Identify common chemical changes in everyday life.

A few children could State clearly that their results are valid because of the various factors they

controlled. Analyse data and suggest an alternative way of ensuring its validity. Know that Hydrogels are classed as smart materials because they change

shape when there is a change in their environment – this determines their ability to absorb.

Make a list of as many different types of “smart materials” that you can find. What are their special qualities that make them ‘smart’?

Take one of the materials you have found and devise an experiment to test its unique properties. (Hint: The internet should give you all the information).

Plenary/Review including Skills Progression focus: Recording and analysis of scientific data and observations What are the unique properties of the hydrogel? Where else could this ability to absorb vast quantities of water be used? What are the advantages and disadvantages of using such a product?

Useful websites

Hydrogel ball video: https://www.youtube.com/watch?v=IPK2m0qRZx4

Green fire tornado video: https://www.youtube.com/watch?v=v6IbKE8hmiQ

Simple chemical reactions explained: http://www.chem4kids.com/files/react_intro.html

Science quizzes – to model or research: http://www.sciencekids.co.nz/quizzes.html

Lovely PowerPoint on simple chemical reactions – some revision: https://www.tes.co.uk/teaching-resource/7f-simple-chemical-reactions-for-sen-6168561

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NOTES:

Chemical Change – Electrochemistry Lessons 3 and 4

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Electrochemistry

Lesson Objectives

Choose from:

Recognise and explain the reasons for a chemical reaction. Make suggestions as to which are reversible and why. Make and record accurate measurements which can be used to explain whether a prediction is correct or not.

Essential Knowledge/ Science Explained – for teachers 1. Combustion is a chemical reaction that produces heat and light. The most common form of combustion is fire.

Most forms of combustion happen when the gas oxygen joins with another substance. For example, when wood burns, oxygen in the air joins with carbon in wood.

2. The idea is to use electricity to coat a relatively mundane metal, such as copper, with a thin layer of another, more precious metal, such as gold or silver. Electroplating has lots of other uses, besides making cheap metals look expensive. We can use it to make things rust-resistant, for example, or to produce a variety of useful alloys like brass and bronze.

3. Money to burn - Money will actually burn if you dip it into a pure alcohol solution. The secret, of course, is the addition of water to the mixture. The water from the water-alcohol mixture absorbs much of the heat energy that is generated when you ignite the note. The temperature of the paper money does not rise above the temperature required to burn the paper. The water is first heated to its boiling point and then vaporized by the heat of combustion from the burning alcohol. If you reduce the amount of water in the mixture, the paper money is likely to char or even catch fire. - See more at: http://www.stevespanglerscience.com/lab/experiments/burning-money#sthash.E3h6nj4Z.dpuf

4. The water in the alcohol-water mixture evaporates as the alcohol burns, keeping the temperature of the paper below its ignition temperature (approximately 230°C). Adding sodium chloride gives an orange colour to the flame.

5. Electroplating - Electricity can be used to initiate chemical reactions (remember the iron wool combustion). Electricity can also be used to split solutions into their component parts. For example, sodium chloride has the formula NaCl. In solution, the sodium and chlorine ‘split’ into what are called ions. These are simply charged particles. Metals have positive charges, and non-metals have negative charges. If you look at the diagram below you can see that opposites attract i.e the metal ion migrates to the negative electrode (called the cathode) and the non-metal ions are attracted to the positive electrode (the anode).

Common Misconceptions

1. Molecules (compounds) are indivisible. A molecule is the smallest identifiable unit into which a pure substance can be divided and still retain the composition and chemical properties of that substance.

2. Fire is a substance. For the most part, fire is a mixture of hot gases. Flames are the result of a chemical reaction, primarily between oxygen in air and a fuel, such as wood or propane.

3. Chemicals react with electricity.

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Termly Scientific Skills Development Focus: Recording and Analysis of Scientific Data and Observations

Collecting and presenting scientific observations in a way that can be analysed. Creating graphs and charts of the data Analysing data the data obtained from the experiment and determining whether or not it proves or disproves the

prediction.

Opportunities should be given throughout the lesson for children to use and develop their knowledge of planning investigations, through questioning and discussions on questions to investigate, making predictions and suggesting dependent and independent variables.

Cross curricular links

Literacy Write an explanation/instructional text for other pupils on electroplating. Compose a news story involving some trickery, such as an amazing robbery where

the money wasn’t burnt! Use the theme of magic to stimulate writing – could be spells, poems, story

planning.

Numeracy Use of scales and symbols in measuring voltage and current. Collect data choosing appropriate numbers, ranges and values for measurements

and observations.

Other subjects

The burning of Chinese paper money (also known as Ghost Money) is an ancient tradition that goes back thousands of years. Find out why it is done.

Try some fun artwork. For inspiration look at images from http://fineartamerica.com/featured/static-electricity-autumn-temple.html

Preparation Label three beakers A, B and C

Place about 50 ml of water in beaker A.

Place a similar volume of IDA in B.

Place a mixture of 25 ml water and 25 ml of IDA in C and add about 1 g of potassium chloride (half the amount provided). Stir until it has all dissolved.

Prior Discussion This is a neat 'magic trick' that illustrates the process of combustion, the flammability of alcohol, and the special qualities of the material used to make currency. Recap definition of combustion – a chemical reaction. Discuss other examples of a chemical reaction.

Teacher Demonstration Money to burn? Apparatus and chemicals Health & Safety: The teacher must wear eye protection Be wary if there are smoke alarms in the room and use the safety screen.

3 x £5 notes (or higher if you're brave enough, you to provide or paper pieces cut to the size of a £5 note can be used instead)

3 x beakers

tongs

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matches

Heatproof mat

3 x 250 ml beakers

Sodium chloride (to produce an orange coloured flame)

IDA (industrial denatured alcohol)

Safety glasses

Safety screen Procedure 1. Discuss with the class what money is made from? What happens to paper when it gets wet? Is burnt etc? Are

these changes reversible? 2. Place the three beakers A, B & C on the desk. 3. Using the tongs, soak the £5 note in Beaker A (water). Move it away from the beaker and hold it over the

heatproof mat. Try to ignite it by holding a match to it for a few seconds. It does not ignite. 4. Using the tongs, soak a second £5 note Beaker B (IDA) let it drain a little. Move it away from the beaker and

hold it over the heatproof mat as you light it with a match just long enough for it to ignite. The alcohol on the paper burns easily and starts to sets fire to the paper, extinguish the flame by dropping it into Beaker A, water. (If the alcohol in Beaker B does ignite by accident during the demonstration, it can be easily and safely extinguished by covering the beaker with the heatproof mat.)

5. Soak the third £5 note in Beaker C (IDA and water mix) and again use the tongs to hold it over the heatproof mat for just long enough to ignite it. Observe as the alcohol burns with a purple flame, but the paper does not burn. The paper will still be wet with water after the alcohol has burnt away. Once the alcohol has burnt away the flame should extinguish itself.

The demonstration looks even more impressive in subdued lighting. The experiment could be extended to include different alcohol-water mixtures and other salts such as sodium chloride or lithium chloride.

Possible Questions/ Suggestions for discussion In this investigation the class will see that electricity causes a metal that is in solution to be deposited on another. Discuss the possibilities of getting the original material back, and which other changes may result in an irreversible change.

Children’s Investigation Electroplating Health & safety: Eye protection must be worn and disposable gloves. Apparatus and chemicals

Stopwatch

Copper sulphate solution (1 M)

Copper strip (2 cm x 6 cm)

Piece of steel sheet (6 cm x 6 cm)

Connecting leads

Crocodile clips

9V cell

Ammeter

150 ml beaker

Gloves

Safety glasses Procedure

Pour about 100 ml of the copper sulphate solution (the electrolyte) into the beaker.

Take the 9V cell and connect it to the ammeter.(See Figure 13 below)

Connect the positive electrode to the copper strip and the negative electrode to the steel sheet. They are the anode (+) and cathode (-) respectively.

Place these into the beaker of copper sulphate solution. There should be some evidence of activity as bubbles form

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around both electrodes. This is because the electrical charge is creating a current within the cell due to the ions present in the electrolytic solution.

In this cell, the sulphate ions remain in solution, while copper ions are deposited on the cathode as they are dissolved from the anode. As the copper ions are constantly being replenished into solution from the anode, causing it to eventually be consumed entirely and re-deposited atom by atom on the cathode. Any impurities present in the anode will settle out of solution at the bottom of the container. The copper deposited at the cathode is very pure. In fact, this method is used in industrial environments to purify metals, the resultant being called "electrolytically pure".

The strip of stainless steel (cathode) shown in Figure 13 develops a light coating of copper when dipped in the copper sulphate solution (electrolyte). The change in colour from silver to orange/brown shows this. Electroplating is widely used in industry as a surface treatment on metals. These treatments can protect the underlying structure from oxidation, or can serve a decorative function. Jewellery makers often deposit very thin layers of gold on base metals to make less costly jewellery with all the appearance of solid gold. In electronics, gold is widely used to coat electrical contacts because of its resistance to oxidation and its long-term stability. Electrolysis can also be used for other surface treatments of metals for decorative and protective purposes. Aluminium is often "anodised" which means that it is used as the anode in a process that oxidises the surface, protecting it from corrosion and achieving various colorations all the way to black. Galvanising puts zinc onto mild steel or iron to prevent it from rusting.

Possible Questions/ Suggestions for discussion

You could try changing the voltage across the cell and control the current flow. Make a chart of the rate of deposition on the cathode as compared to the current flow over fixed periods of

time. Pupils can suggest ideas about what they think happen to the two electrodes. Get children to come up with ideas of how they could more accurately control the electroplating of the steel

plate. Ask them if they know of any processes where this is used like silver and gold plating for example.

Learning Outcomes All children should

Use simple scientific equipment for electrolysis (ammeters, batteries and electrodes)

Describe electroplating with copper. Choose appropriate numbers for measurements and observations. Make careful observations linked to a prediction. Recognise a chemical reaction.

Some children could Use appropriate methods and resources safely and correctly. Choose appropriate numbers, ranges and values for measurements and

observations. Recognise a chemical reaction and explain why it has happened. Identify changes which may or may not be reversible.

A few children could Select appropriate ways of presenting scientific data. Explain in simple terms how electrolysis is used in industry.

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Plenary/Review including Skills Progression focus: Recording and analysis of scientific data and observations What are the purposes of electroplating metals? What are the additional properties that electroplating gives to the metal it is plated on to? What are the advantages and disadvantages of electroplating? How can we record what we observed? How valid is our data? Can our data be used to answer our question?

Useful websites

Electroplating explained: http://www.explainthatstuff.com/electroplating.html Electroplating video (by a 7 year old!): https://www.youtube.com/watch?v=LqJwrUEh6Ek Investigation to try at home: http://sciencewithkids.com/Experiments/Chemistry-experiments/copper-plating-experiment.html Copper facts: http://www.ducksters.com/science/chemistry/copper.php

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NOTES:

Chemical Change – Investigating Chemical Structure Lessons 5 and 6

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Chemical Structures

Lesson Objectives

Choose from: Understand that the structure of a material changes during a reaction, which is why sometimes the reactions

are irreversible. Decide upon an appropriate method to collect and record data, and use to explain whether a prediction is

correct or not.

Essential Knowledge/Science Explained – for teachers

1. Chocolate is a mixture of many chemicals of which about 400 have been identified. Taste, texture, gloss, 'snap' and other properties can be varied according to how the mixture is processed. Manufacturing chocolate is a complex multi-step process. Making a chocolate bar begins with mixing the ingredients and grinding them to give a mixture of correctly sized particles. Size is critical to the 'mouth feel' of the product, and is typically about 0.02 mm. The next stage is known as 'conching' and involves removing volatile compounds and adjusting moisture content and viscosity. This gives the end product its desired flavour. The mixture is melted, stirred and cooled in a complex process known as tempering. The temperature and stirring have to be very carefully controlled or the chocolate ends up brittle, crumbly and tasting different. A key ingredient is cocoa butter. It is a fat and it can come in at least six different crystalline forms. This means that the atoms are the same but they are arranged differently. The different arrangements can lead to different properties including melting point, how easily it snaps, strength, glossiness and texture. It’s a bit like Lego bricks. You can use the same bricks to make different structures; some are stronger, and some look better. The ability of the structure to take on many different crystalline forms is called polymorphism ('poly' means many; 'morph' means shape).

Common Misconceptions

1. Particles ‘change’ in chemical reactions. Reactions occur when two or more molecules interact and the molecules change. Bonds between atoms are broken and created to form new molecules.

2. When reactants are used up, they ‘vanish’. In a chemical reaction, the atoms and molecules that interact with each other are called reactants. In a chemical reaction, the atoms and molecules produced by the reaction are called products. In a chemical reaction, only the atoms present in the reactants can end up in the products. No new atoms are created, and no atoms are destroyed.

3. New materials are always made. A physical change, such as a state change or dissolving, does not create a new substance, but a chemical change does.

4. Mass reductions in chemical reactants are the result of substances being destroyed.

Termly Scientific Skills Development Focus: Recording and Analysis of Scientific Data and Observations

Collecting and presenting scientific observations in a way that can be analysed. Creating graphs and charts of the data Analysing data the data obtained from the experiment and determining whether or not it proves or disproves the

prediction.

Chemical Change – Investigating Chemical Structure Lessons 5 and 6

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Opportunities should be given throughout the lesson for children to use and develop their knowledge of planning investigations, through questioning and discussions on questions to investigate, making predictions and suggesting dependent and independent variables.

Cross curricular links

Literacy Make a fact file about chocolate. Create recipes using chocolate for work on imperative verbs. Write up one of the investigations as a report or explanation text. Add to the class glossary on Chemical Changes.

Numeracy Estimating and measuring temperatures. Recording observations and measurements in a table which could be graphed. Children could create and answer word problems using measuring, chocolate etc.

They could then swap and answer each other’s.

Other subjects Prepare a project on the story of chocolate;

http://www.historyforkids.org/learn/food/chocolate.htm. This could be in the form of an animation, comic strip or traditional project.

Create beautiful artwork from the milk and detergent investigation. Try looking at the work of Sophia Ruting as an example.

Preparation

Milk and chocolate buttons will need to be bought prior to the lesson. Store both items in the fridge until just before use. Organise practical and delivery and set up of equipment in the classroom.

In Experiment 1: You will need to place the milk in the plates otherwise it could get very messy and milk isn’t easy to clean up. Allow the children to take a beaker containing about 5 ml of the detergent; they only need enough to coat the tip of the cotton bud.

Prior Discussion Spend some time discussing changing states. Which chemical reaction would be needed to change:

Paper to ash? Bread to toast? Water to ice? Water to water vapour?

In each case, which other reactions have also taken place? Is it possible to get back the original material?

Teacher Demonstration Demonstration - Changing chemical form with calcium carbide and water and combustion of acetylene. HEALTH & SAFETY: The teacher should be wearing eye protection and disposable gloves. Apparatus & chemicals

Safety screen

Safety glasses

Disposable gloves

Small pieces of calcium carbide

Boiling tubes

Wooden splint

Clamp stand, boss and clamp

Matches.

Chemical Change – Investigating Chemical Structure Lessons 5 and 6

LP5&6 CCC001 V1 25 08 15 |Page 3

Procedure

Ask children to name some chemical reactions where it is more likely that a new material is made and the original is altered.

Take the clamp stand and set up the clamp securing it in place with the boss.

Then position the boiling tube in the clamp so it is vertical. Set this all up behind the safety screen.

At this point get all the children to gather around the desk, about a metre away from the screen.

Half fill the boiling tube with water and add one piece of the calcium carbide to it, the reaction starts immediately.

Light the splint and then place it at the top of the boiling tube, the acetylene produced is highly flammable and will catch alight and burn with a bright yellow flame. Once the acetylene has all burned away you can add another piece and repeat the experiment.

Possible Questions/ Suggestions for discussion The reaction is very quick and is almost literally a ‘flash in the pan’. Ask the children to discuss or record:

Which reaction did you see? What does that prove? Any other chemical reactions? What was produced? Can it be reversed? When else have you seen a chemical reaction which happens quickly? (icing sugar tin)

Share answers as a class to provide some useful discussion points and to clear up any misconceptions. Somebody could also list vocabulary used.

Children’s Investigation Experiment 1: Milk & Detergent Introduction to Investigation 1 This activity is a fun and exciting experiment. The children love doing it and find it really interesting. It is a good introduction to show how a detergent can make a big difference to how mixtures and solutions behave. Apparatus

Whole milk

Plastic plates

Cotton buds

25 ml plastic beakers

Food colourings

Washing up detergent Procedure Health & Safety: Check no one has a serious allergy to milk or dairy products.

The children work in pairs, each pair with a plate and a beaker of the detergent

Next pour some of the milk onto their plate (just sufficient to cover the base of the plate completely).

Pass around the food colourings. One member of the pair will need to add a few drops of each of the four food colours in the centre of the milk so that they start to mix together slightly, but not too much.

Next the other member of the pair can take the cotton bud and dip one end of it into the beaker of detergent coating it well.

Take the bud and place it in the middle of the milk holding it completely steady DO NOT STIR.

The effect should speak for itself, the result is amazing. Check out the link for the video. http://www.youtube.com/watch?v=pW-bn9zssak

Chemical Change – Investigating Chemical Structure Lessons 5 and 6

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Experiment 2: Structure of Chocolate Introduction to Investigation 2 Children are going to melt the chocolate and then taste both the melted and original chocolate to compare them. This activity is a good introduction to how structure can make a big difference to the properties of a substance. It’s also fun to do, interesting, and the taste tests are always popular! Apparatus

Aluminium foil

Milk chocolate buttons

Tea lights and holders

50 ml glass beakers

Stirrers

Ice

Thermometer

250 ml plastic beakers

Hot water at approximately 50°C Procedure Health & Safety: All the pupils will need to wash their hands as they are going to be handling a food product which they are going to eat. Check that no one is allergic to dairy products or chocolate before starting.

Give each pair two pieces of foil and four chocolate buttons. They place two chocolate buttons into each piece of foil.

Make sure that all the foil is sealed up and that no water can seep in. They are going to take one of the pieces of foil and place it in a beaker of hot water to melt the chocolate. The other piece is left to compare later. The foil helps to keep the chocolate clean and free from contamination as they will taste them later.

Half fill the 50 ml glass beaker with hot water at about 50°C (water from the hot tap is normally about 55°C, if not you may need to heat it up using the tea light). Use the thermometer to check the water temperature.

Place the piece of foil containing the two chocolate buttons on the water in the beaker.

The foil should float on top of the water, but the heat should be sufficient to melt the chocolate buttons. Give the foil a stir round to make sure that all of the foil is heated by the water. Keep checking the temperature of the water and if it seems to be cooling down place the beaker over the lit tea light in its holder. Do this for about 10 minutes.

Get the children to carefully remove the foil from the beaker and gently feel the foil to it is soft. If so then the chocolate has melted.

Now get them to put a couple of ice cubes in the bottom of the 250 ml plastic beaker and then place the foil packet in the beaker onto the ice cubes until it has cooled.

Next, children need to wash their hands again as they are going to open up both pieces of foil and compare the original chocolate buttons with the melted and reset version.

Children should make a note of their observations and compare the appearance, colour, smell and the brittleness of it with the original chocolate buttons.

Then they can do the ultimate test ‘the taste test’.

What has the effect of heating the chocolate had on its flavour compared to the original one?

Possible Questions/ Suggestions for discussion

Milk and detergent: Milk consists of a lot of different types of molecules, including fat, protein, sugars, vitamins, and minerals. If you had just touched a clean cotton swab to the milk (try it!), not much would have happened. The cotton is absorbent, so you would have created a current in the milk, but you wouldn't have seen anything especially dramatic happen. When you introduce detergent to the milk, several things happen at once. The detergent lowers the surface tension of the liquid so that the food colouring is free to flow throughout the milk. The detergent reacts with the protein in the milk, altering the shape of those molecules and setting them in motion. The detergent breaks down the fat globules, which is how detergent helps to lift grease off of dirty dishes. As fat globules break down, currents form in the milk which pushes the food colouring around. The swirling of the colours continues for quite a while before stopping.

Chemical Change – Investigating Chemical Structure Lessons 5 and 6

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Chocolate: The taste of the chocolate is partly determined by the recipe used in making the product but there is more to it than that. This is because the taste of chocolate depends on the micro scale structure of the chocolate. Chocolate is made up of tiny particles and crystals between 0.01 and 0.10 mm in diameter. These govern the texture of the chocolate. To taste something, the flavours have to reach the mouth and the nose, but the texture is important too. The overall taste is a result of both chemical make-up and also how the material melts and breaks up in the mouth.

Students should compare the appearance, colour, smell and the brittleness of it with the original chocolate buttons.

Then they can do the ultimate test ‘the taste test’.

What has the effect of heating the chocolate had on its flavour compared to the original one?

Learning Outcomes All children should

Classify objects / substances. Use a scientific model to explain observations. Link uses of materials to their characteristics or properties. Name a range of chemical reactions.

Some children could Decide on an appropriate form to record and present data. Be able to analyse a chemical reaction and describe changes in state and

where each product ends up.

A few children could Explain polymorphism and define it. Use appropriate scientific language to communicate scientific ideas,

processes or phenomena. Suggest other ways to record data.

Plenary/Review including Skills Progression focus: Recording and analysis of scientific data and observations

What do the children think has happened to the chocolate?

Why should heating the chocolate affect its appearance and taste?

What chemical change would be needed to return the material to its original state?

What have they learned from these experiments?

How did you choose to record your data/observations?

Could your recording be improved? If so, how?

Useful websites

The science of chocolate: http://www.sciencekids.co.nz/videos/chemistry/chocolate.html Or: http://www.sciencefriday.com/blogs/06/04/2014/chocolate-crystal-concoctions.html Chemical reactions explained: http://www.ducksters.com/science/chemistry/chemical_reactions.php Simple chemical reactions with food: http://www.bbc.co.uk/education/clips/z9wkjxs Reversible and irreversible changes: www.bbc.co.uk/bitesize/ks2/science/materials/reversible_irreversible_changes/read/1/

Chemical Change – Investigating Chemical Structure Lessons 5 and 6

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NOTES:

Chemical Change – Irreversible Chemical Changes Lessons 7 and 8

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Irreversible Chemical Changes

Lesson Objectives

Choose from:

Understand and explain the process of an irreversible change. Make a prediction that can be tested and use your data to support it.

Essential Knowledge/Science Explained - for teachers

1. Soda Snake: The sodium hydrogen carbonate releases carbon dioxide when heated above 50 °C. Burning the alcohol caramelises the sugar, giving the snakes their black appearance. The snakes grow because of the pressure from the carbon dioxide gas being released. The reaction stops when all the alcohol has burned.

2. Concrete is a mix of cement, sand, gravel and water. Pupils make some concrete and include various additives in the mix. They investigate how changing the additives changes the properties of the resulting composite.

3. A composite material is made by combining two or more materials – often ones that have very different properties. The two materials work together to give the composite unique properties. However, within the composite you can easily tell the different materials apart because they do not dissolve or blend into each other.

Making concrete is an irreversible reaction because all the individual components have combined to form a compound that cannot be broken down and returned to its original form, i.e. All the reactants have been converted to form the product. In a reversible reaction the reactants and products are said to be in equilibrium at any time. E.g.,

A reversible reaction is a chemical change in which the products can be converted back to the original reactants under suitable conditions.

In other words, you can change the position of the chemical

A reversible reaction is shown by the sign , o a half-arrow to the right (direction of forward reaction) o a half-arrow to the left (direction of backward reaction)

Most reactions are not reversible (irreversible) and have the usual complete arrow only pointing to the right.

http://www.docbrown.info/page04/4_74revNH3.htm

Common Misconceptions 1. Reactants ‘equal’ products in chemical reactions - A chemical reaction involves atoms in

the reactants being rearranged to form the products. No material is lost or gained. 2. All chemical reactions are irreversible.

3. A substance is not a chemical if it doesn’t react with anything,

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Termly Scientific Skills Development Focus: Recording and Analysis of Scientific Data and Observations

Collecting and presenting scientific observations in a way that can be analysed. Creating graphs and charts of the data Analysing data the data obtained from the experiment and determining whether or not it proves or

disproves the prediction. Opportunities should be given throughout the lesson for children to use and develop their knowledge of planning investigations, through questioning and discussions on questions to investigate, making predictions and suggesting dependent and independent variables.

Cross curricular links

Literacy Write a newspaper report on the invention of a new type of chocolate

that doesn’t melt – possibly by the marvellous Willy Wonka. Make or add to a class science dictionary of terms and definitions. Research into the work of the famous chocolatiers Teuscher, and

write a report.

Numeracy Calculating simple formulations using measurements of teaspoons

accurately and recording the data. Tabulating and/or graphing data recorded. Calculate averages using class data.

Other subjects

Find out about the many different uses there are for concrete? What additives are put into commercially made concrete and why? What methods are used to strengthen it for its different applications?

The development of concrete altered Roman architecture – find out how and why?

Make and decorate concrete leaves for the school garden area. http://anotherjennifer.com/kid-friendly-urban-garden-art-project-concrete-leaves/

Alternatively, groups could make some concrete stepping stones for an outdoor area. http://www.houselogic.com/home-advice/landscaping-gardening/ideas-kids-projects/

Preparation

For the investigation you will need lots of newspaper it maybe an idea to get the children to each bring in a newspaper from home.

Photocopy moulds onto thin card you will need lots of these if each pair is going to make several different composites.

Organise practical and delivery and set up of equipment in the classroom.

Children should work in pairs. Each pair needs two mould templates to cut out and stick together in preparation for the concrete mix. (These ideally should have been photocopied onto thin card)

To make it easier for the children to differentiate between composites they could be use different coloured moulds, so photocopy onto different coloured card. Once the concrete has set, the mould will need to be removed but this can be left until just before the testing is carried out which will be at the start of the next lesson.

Pupils need two lessons to complete the investigation. In the first lesson, they prepare the samples and leave them to set. In the second lesson, they test their samples for strength.

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Prior Discussion Explain that you are about to carry out a demonstration which has links to one they may have seen before. Ask children to try to remember where they have seen something similar, and the theory and vocabulary used previously. (Children may suggest Elephant’s Toothpaste).

Teacher Demonstration Demonstration – Soda Snake Firework HEALTH & SAFETY: The teacher should wear eye protection. Apparatus and chemicals

Heatproof mat

Sand

Four teaspoons of icing sugar

1 teaspoon of sodium hydrogen carbonate

20ml Propan-2-ol (alcohol)

Matches

Teaspoon

Safety glasses

Procedure Take the heatproof mat and make a mound in the middle with the sand. In the centre of the mound make a dent with your finger. Pour some of the alcohol into the dent taking care not to collapse the mound. Mix the icing sugar and sodium hydrogen carbonate together in the plastic cup and fill the dent. Light the mixture with a match and stand back as the alcohol starts to burn. Little black balls appear and the snake starts to grow from inside the mound. Eventually the snake will emerge and it is an amazing sight to behold. Warning: Do not under any circumstances pour any more alcohol on the mound whilst the reaction is taking place, as isopropyl alcohol is highly flammable and it could flare up and cause severe burns. This experiment can get very hot, so it is important that it is performed on a heatproof mat or heatproof surface. The reaction should be performed in a ventilated room. No smoke is produced, but the alcohol vapour has a tendency to smell. Make sure that the sugar and baking soda fills the indentation evenly, otherwise your snake may appear with mutant legs and eyes! Making a narrow, deep indent in the sand with your little finger or a pencil will help to make your snake tall and slim.

http://www.sciencemuseum.org.uk/~/media/85A2FB9FF588413C81F2E94757C35547.ashx

Possible Questions/ Suggestions for discussion

What did you observe? What was actually happening? Who can explain it in terms of a chemical change?

Children’s Investigation Class activity – Experiment : Making and testing concrete Pupils make some concrete and include various additives in the mix. They investigate how changing the additives changes the properties of the resulting composite. Concrete is a mix of cement, sand, gravel and water. Apparatus and chemicals per pair

3 table spoons of Cement

2 cups of fine sand

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1 cup of gravel

12 paper clips

2 lollipop sticks

1 plastic cups

4 splints

3 moulds (template below, prior to lesson photocopy onto card)

1 pritt stick (to use in mould assembly)

2 plastic tea spoons

1 mass hook

1m string

500g mass

Safety specs

Disposable gloves

Part 1 – Making Concrete Procedure Health and safety: Cement is corrosive. Eye protection to be worn by all and try to avoid raising cement dust. Avoid skin contact with the cement. Disposable gloves to be worn by all.

Cover your bench in newspaper. Collect a plastic cup, put two teaspoons of cement powder, four teaspoons of sand and six teaspoons of gravel in the cup and mix them together thoroughly.

Add water a drop or two at a time. It is easier to add water than to remove it from the mixture and not much is required so add it carefully. Keep mixing until a hole made in the mixture will remain but it can also be poured.

Pour the mixture into a mould. Label the mould with your name and ‘Sample 1’ and then leave the mixture to set.

Make other samples and include different additives or vary the mixture in other ways. Include some or all of the following: no gravel; wooden splints placed in the mould and the cement mixture added to it; opened paper clips or wire in the mould and the cement added to it; Plaster of Paris powder added to the mix. You could also change the size of the gravel pieces or the ratio of cement, sand and gravel in the mixture.

For each sample you make, record what it contains in a table like the one below:

Sample number Composite mixture Mass required to break it

1

2 teaspoons cement,

4 teaspoons sand,

6 teaspoons water

2

3

When the pupils have finished making their samples, get them to place them all in a safe place to set. Wrap up the newspaper on the desks, making sure they collect all the dust and bits. Put this into the rubbish bin, along with your plastic mixing cup, stirrer and gloves. Do not wash up anything that has had cement powder on it. Make sure the children wash their hands.

Part 2 - Testing concrete Pupils are going to test the concrete bars they made last lesson to see how much weight they can bear before they snap. This is a measure of their tensile strength.

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Health & Safety: Safety glasses should be worn by all, as pieces of concrete could fly out when the composites break. Can the pupils predict which composite they think will be the strongest and which the weakest of their samples? Record this at the side of their results tables. Set up and demonstrate as shown below and explain how they will carry out the tests, emphasise the safety aspects, such as making sure the bubble wrap is correctly in place under the hanger. They must keep their feet away from the area to avoid broken toes.

1. Each pair of pupils should take: Safety glasses, their thoroughly set hard composite samples, a G clamp,

several 100 g masses, one mass hanger, some string, and a piece of bubble wrap about 60 cm x 30 cm 2. Pupils should fold the bubble wrap double and place on the floor under the mass hanger to absorb the

impact of the weight when it falls. 3. Get children to set up their sample to test as in the diagram above and your demonstration. 4. They should add one 100 g mass to the hanger at a time and continue to do this until the sample

eventually breaks. Make a note of this in the table. Bear in mind that the hanger itself is a 100 g so when one mass has been added there will be 200 g in total and so on. They may be surprised as to how much weight it will take to break it. Nine masses plus the hanger is 1 Kg and it could take that and more for some of the composites to eventually break.

Possible Questions/ Suggestions for discussion

What other additives could be tried in the mix? How could the concrete be made even stronger? How might this experiment be improved on in the future? What other materials could this kind of test be used for? How else could you record your data and what else could you test?

Learning Outcomes All children should

Practise the skill of making a prediction. Control variables. Collect data using appropriate ranges, numbers, values, for

measurements and observations. Learn that chemical reactions are either reversible or

irreversible.

G-clamp

Bench

Bubble wrap

Concrete

Strong loop of string

Weights on hooks

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Some children could Explain their observations using justified arguments. Recall that exothermic reactions increase temperature and

endothermic reactions decrease temperature.

A few children could Independently undertake a practical technique. Know that a composite material is made by combining two or

more materials – often ones that have very different properties.

Plenary/Review including Skills Progression focus: Recording and analysis of scientific data and observations

1. Did the results match the predictions? Were there any surprises? Discuss what the children discovered from

the results. 2. Were the results reliable and can any conclusions be drawn from them as to what composition makes the best

and strongest concrete? 3. Is this a fair test? Is there a better method of testing the concrete? How could it be improved? 4. From the results what particular additive in the strongest composite can be identified as the ingredient that

made the difference between it and the other composites?

Useful websites History of concrete: http://www.historyforkids.org/learn/architecture/concrete.htm Or: http://www.teachprimary.com/learning_resources/view/ks2-science-the-romans Soda Snake video: www.youtube.com/watch?v=8jNG8w0lJ4U

Template mould for making concrete

Shaded tabs, place glue on the outside to stick to the inside of side

pieces

Chemical Change – Observing and Measuring Chemical Changes Lessons 9 and 10

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Observing and Measuring Chemical Changes

Lesson Objectives

Choose from: Know that some materials dissolve in a liquid to form a solution, and that others may not. Explain what happens to a material during a chemical reaction. Make careful observations using scientific equipment and use to explain your ideas.

Essential Knowledge/Science Explained – for teachers 1. The Blue Bottle Reaction: An alkaline solution of glucose acts as a reducing agent and changes methylene blue

from a blue to a colourless form. Shaking the solution raises the concentration of oxygen in the mixture and this changes the methylene blue back to its blue form. When the dissolved oxygen has reacted, the methylene blue is slowly reduced back to its colourless form by the remaining glucose; the cycle can be repeated many times by further shaking. For this reason the methylene blue is known as a Redox Indicator. For more information on Redox Indicators follow the link: http://en.wikipedia.org/wiki/Redox_indicator

2. Chemical worms: Sodium alginate is a natural polymer which can be extracted from giant kelp (brown seaweed). It is one of the polymers that help to build the cell walls of these plants. It has some unusual properties and a wide variety of uses. When sodium alginate is put into a solution of calcium ions, the calcium ions replace the sodium ions in the polymer. Each calcium ion can attach to two of the polymer strands. This is called crosslinking and turns the solution into a gel. Alginate is used in many applications e.g. Gaviscon and new ones are being found all the time. It is used in the food industry, medicines and dental impression materials. Calcium alginate (the cross-linked polymer) is used in wound dressings. Part of the blood clotting mechanism involves calcium ions. On contact with blood, the calcium alginate releases calcium ions in exchange for sodium ions as observed in the experiment above. These extra calcium ions help the blood to clot and encourage healing.

http://www.scitech.qut.edu.au/documents/community/events/pd/Polymers/Teacher_guides/AlginateWorms.pdf

Common Misconceptions

1. Once a material has dissolved, it has disappeared. No, the molecules have simply become incorporated into a

liquid. 2. Steel or Iron only requires the presence of oxygen to rust. Water is also necessary for the process.

Termly Scientific Skills Development Focus: Recording and Analysis of Scientific Data and Observations

Collecting and presenting scientific observations in a way that can be analysed. Creating graphs and charts of the data Analysing data the data obtained from the experiment and determining whether or not it proves or disproves the

prediction.

Opportunities should be given throughout the lesson for children to use and develop their knowledge of planning investigations, through questioning and discussions on questions to investigate, making predictions and suggesting dependent and independent variables.

Cross curricular links

Literacy Chemical worms may inspire some poetry (personification) or work on adjectives and adverbs.

Comic strip style pieces on the use of concrete.

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Numeracy Take accurate measurements and control time intervals.

Other subjects

List other occasions when colour changes occur: in nature – chameleon, leaves, or materials when wet – sand. You could even find out about Rachel Riley’s famous dress.

Painting with Sound. Using music to inspire colour changing artwork. A similar example is available at https://www.tes.co.uk/teaching-resource/ks2-music-unit-13-painting-with-sound-cornwall-6304652

Preparation

For the demonstration (less than 20 minutes beforehand, preferably) HEALTH & SAFETY: Eye protection should be worn by the teacher.

Take one of the pots of methylene blue, unscrew the lid and add 50 ml of the alcohol.

Next take one of the pots of potassium hydroxide and empty the contents into the Schott bottle, add 300 ml of water and 10 g of glucose and swirl until the solids are dissolved. Add 5 ml of the methylene blue solution. The exact quantity used is not critical.

Use the mass balance to weigh the glucose.

The resulting blue solution will turn colourless after about one minute. Screw the top onto the bottle.

For the investigation: Prepare the two solutions needed. Add the stated amount of water to the calcium chloride powder. Shake well. Repeat with the sodium chloride powder. Decant into smaller quantities for the children to use.

Prior Discussion Have you ever been told to bring your bike in out of the rain? Have you ever wondered why? After all, rain is just water, and the rain could clean your bike, right? The problem is that some parts of your bike are made of steel. Steel sounds like a strong metal, and it is, but the main element in steel is iron, and in the presence of water, iron combines easily with another element, called oxygen, to form iron oxide, also known as that reddish-brown substance called rust. (Corrosion) Rust changes steel into a different material, one that is weaker than the original steel. Rusting is a big problem because so many things people use every day are made out of steel, like cars, trucks, bridges, roofs, machinery, nuts, and bolts. When these objects are unprotected and exposed to water, they rust, and this damage costs a lot of money. Today you are going to mimic the different conditions that cause iron to rust.

Teacher Demonstration The Blue Bottle Reaction HEALTH & SAFETY: The teacher should be wearing eye protection. Apparatus & Chemicals

1000 ml Schott bottle with screw top lid

400 ml glass beaker

Potassium hydroxide (Corrosive), 8 g

Glucose (dextrose) (Low hazard), 10 g

Methylene blue (Harmful), 0.05 g

Ethanol (IDA – Industrial Denatured Alcohol) (Highly flammable, harmful)

Mass balance

Safety glasses

Chemical Change – Observing and Measuring Chemical Changes Lessons 9 and 10

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Procedure You may wish to present this experiment as a magic trick. Alternatively you could use this as a discussion on dissolving, for example where are the particles? Which materials dissolve etc.

Take the bottle containing the solution you prepared earlier. Screw the lid securely in place; shake it vigorously so that air dissolves in the solution.

The colour will change to blue and will fade back to colourless over about 30 seconds.

The more shaking, the longer the blue colour will take to fade.

Alternatively for a more dramatic effect you can pour the solution into the large beaker and then back into the bottle and vice versa.

After some hours, the solution will turn yellow and the colour changes will fail to occur.

A white background helps to make the colour changes more vivid.

On a cold day it may be necessary to warm the solution to at least 20 °C otherwise the changes are very slow. This can be done by running the base of the flask under the hot water tap for a few minutes.

Possible Questions/ Suggestions for discussion Expected responses from children are:

Something is on the stopper causing the solution to turn blue when the flask is shaken. There are two colourless liquids in there and they mix to cause the colour change. Shaking the solution adds heat and causes the colour change. The contents then cool and the blue colour fades.

Children’s Investigation Class activity – Experiment 1: Rusting of Iron Wool (Corrosion) Apparatus and chemicals Health & Safety – Safety glasses and gloves to be worn by all. Each pair will need:

2 Thermometers

2 EPS cups with lids

6 cm iron wool

1 pair scissors

1 Ruler

Lemon juice

Tap water

pH paper (3 pieces)

Disposable gloves

Safety glasses Procedure In this experiment the pupils are going to see the effects of acid compared to tap water on iron wool. For this activity, the children work in pairs. Each pair and the teacher need to put on some disposable gloves before handling the iron wool (it is quite easy to get metal splinters from it, so gloves should be worn). The teacher must cut the iron wool into 6 cm pieces and get the children to measure each piece before they put them in the cups as they are going to re-measure them at the end of the experiment. After the experiment the solutions can be washed down the sink and the cups and iron wool thrown in the bin.

1. Get each pair to collect their apparatus: A ruler, 2 EPS cups and lids, 2 thermometers, some pH paper, a piece of iron wool about 6cm long (they are going to cut it into half measure both pieces accurately using the ruler and place one piece into each cup).

2. In one cup they will pour some tap water, just enough to cover the iron wool. Make sure they press it down well, so it is firmly fixed in the bottom of the cup.

3. In the second cup they will pour some lemon juice, again just enough to cover the iron wool.

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4. They need to take a piece of the pH paper rip it in half dip one piece in the lemon juice and one piece in the tap water to test the pH of each solution and measure the initial temperature with the thermometer, which should be room temp ( approx. 20°C).

5. Place the lids on the cups and insert a thermometer into each one through the centre hole in the lid. The reaction will already have started and it is important to note the temperature initially and at regular intervals (e.g., every minute for the next 10 mins.).

6. At the end of the experiment, get the pupils to check the pH of the two solutions as the oxidation occurs; you would expect the pH to change and become less acidic. Also get the pupils to inspect the iron wool to see if there is any notable difference in the two pieces. How do they compare to the initial measurements?

Class activity – Experiment 2: Chemical Worms Apparatus and chemicals Health & Safety: Wear eye protection and gloves. Although the chemicals are all low hazard they might sting if you got them in your eyes. • 25 ml Gaviscon (which contains sodium alginate) • 100 ml 1% w/v Calcium chloride solution (irritant) • 75 ml saturated Sodium chloride solution • 2 sealable glass jars (approx. 150ml each) • Labels for jars • 10 ml plastic syringe (without needle) • Safety glasses • Gloves

Procedure Forming calcium alginate:

Pour the calcium chloride solution into one of the sealable jars (Label it Ca2+

)

Take up some of the Gaviscon into the syringe and gently squeeze out a thin stream into the calcium chloride solution by gently and slowly pushing in the syringe plunger.

Flexible, translucent “worms” will form instantly as the sodium ions are exchanged with calcium ions and the polymer becomes cross linked. The longer the calcium alginate is in contact with the calcium chloride solution, the more rigid the worms will become.

You can lift the worms out of the solution to feel their texture.

Removing the cross-linking the calcium alginate polymer:

Pour some of the saturated sodium chloride solution into the other jar (Label it Na+).

Take a few worms from the Ca2+

jar (as soon as they are formed) and drop them into the Na+ jar. Shake both jars,

after a few shakes the cross linked polymer in the jar of brine (saturated sodium chloride) will dissolve and form a cloudy solution, while the alginate worms in the calcium chloride solution will remain intact.

Pupils should make a table of their results of time intervals and temperature measurements and include observations of the visual effect that hopefully has occurred and/or the pH values, depending on age and ability. More able pupils could produce a graph of Time v Rise in temperature. Ask pupils how the iron wool could be measured more accurately, bearing in mind that measurements aren’t all about size. (i.e. weight) This could be done by weighing the mass of the wool both before and after the reaction.

Possible Questions/ Suggestions for discussion Experiment 1 What happens to iron wool in the presence of acid? ( It rusts quickly) What happens to iron wool in the presence of water? ( It rusts slowly) What is rust and what is its chemical name? (Iron oxide) Where have you seen this reaction before? (Burning iron wool) What type of reaction is taking place? (Exothermic) The reaction is an exothermic one which means that heat is released by the reaction. This heat increases the rusting effect on the iron wool: the combination of the acid and heat speeds up the reaction. Hence the rusting effect should be greatest on the iron wool in the lemon juice.

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For more technical detail and excellent pictures of the effects of rusting, follow the link: http://www.sciencebuddies.org/science-fair-projects/project_ideas/Chem_p079.shtml

Experiment 2 What is alginate an example of? (polymer) Where can it be found? (seaweed) Where have they come across other materials which react in a similar way?

Learning Outcomes All children should

Use scientific language when explaining simple scientific ideas or phenomena.

Make observations or measurements, identifying the ranges and intervals used.

Know that chemical reactions occur at a range of different speeds. Give examples of some of the factors that affect the rates of a reaction e.g.

temperature, movement, catalysts.

Some children could Make observations and analyse the results. Propose scientific explanations for unexpected observations or

measurements making allowance for anomalies. Give examples of slow, medium and fast reactions e.g. – rusting, growth of

organisms, fermentation, and explosions.

A few children could Explain the terms corrosion and polymerisation.

Know that the speed of chemical reactions is affected by ‘Surface area’ – the greater the surface area the faster the reaction.

Develop an understanding that the chemical structure of solids differs thereby causing different chemical reactions.

Plenary/Review including Skills Progression focus: Recording and analysis of scientific data and observations

Get the pupils to enter a discussion and kick off with these little mind bogglers.

Why were the ‘worms’ able to be so firm and stable in the Ca2+

solution? Why did the ‘worms’ become unstable and in fact dissolve in the Na

+ solution?

What do the results obtained tell us about the reaction of the alginate firstly with the calcium chloride and then with the sodium chloride?

What have we learned from this experiment about polymers and how they are formed? Answers will clearly vary from the realisation that a different reaction took place, to an understanding that the chemical structure of the solids used must be different.

Useful websites Endothermic and exothermic reactions explained: http://www.sciencemadesimple.co.uk/chemistry-blogs/exothermic-and-endothermic-reactions https://www.youtube.com/watch?v=yvyHVA1Ww_M Sodium ethanoate in a different form – reminder: http://www.bbc.co.uk/bitesize/standard/chemistry/revision_videos/endothermic_exothermic/video/

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