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Particle Theory & Chemical Reactions

Lesson Plans

Chemistry Lesson Plans – Particle Theory & Chemical Reactions

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PARTICLE THEORY

Each lesson plan contains some Essential Knowledge. This is meant for adults, and is not the content to be taught directly to children.

Prior Knowledge

This unit should begin with a discussion/explanation of the basic particle theory.

Particle theory helps to explain properties and behaviour of materials by providing a model which enables us to visualise what is happening on a very small scale inside those materials. As a model it is useful because it appears to explain many phenomena but as with all models it does have limitations.

Particles in Solids Particles in Liquids Particles in Gases

are held tightly and packed fairly close together - they are strongly attracted to each other

are in fixed positions but they do vibrate

are fairly close together with some attraction between them

are able to move around in all directions but movement is limited by attractions between particles

have little attraction between them

are free to move in all directions and collide with each other and with the walls of a container and are widely spaced out

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 a lesson plan and video demonstrations to serve as reminders. Time can then also be spent on the skills focus, ie 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.

http://www.champaignschools.org/science/images/matter.jpg

Chemistry Lesson Plans – Particle Theory & Chemical Reactions Lessons 1 & 2

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Lessons 1 & 2: Particle Theory & Diffusion

Essential Knowledge/Science Explained – for teachers

1. All matter is made from many tiny particles that are constantly moving. The amount of movement they make

depends on the amount of energy they have and their relationship to other particles.

2. The whoosh bottle contains a highly flammable mixture of alcohol vapour and air, which is ignited. Although the

alcohol was poured out, there still remained some ‘particles’ of alcohol (C2H5OH) vapour that reacts with oxygen

when ignited. The energy released comes from the breaking and forming of chemical bonds. In this case CO2(g) +

H2O(g).

3. Diffusion is the movement of one type of gas molecules through another. The molecules of air in the room and

the molecules of perfume in the spray are all moving around quickly and randomly. The molecules of perfume

collide with other molecules of their own type and also with air molecules. It is very unlikely for any one perfume

molecule to be able to move across the room without hitting another molecule of one type or the other but they

will eventually get there after many collisions. This slow erratic progress is called diffusion. They will eventually

make it to the other side but it will take time.

Common Misconceptions

1. Gases are not matter because most are invisible. 2. Gases do not have mass. 3. Air and oxygen are the same gas. 4. That space between particles is filled. 5. Gas particles evaporate and disappear. 6. Particles can change form, examples include thinking that particles can expand, contract, break up and/or are static.

Health and Safety Precautions

Please read the specific lesson Risk Assessment for details of procedure and equipment.

1. Ensure children are aware of the rules of science: a) Regular hand washing. b) Nothing is to be put in their mouths or eyes. c) Follow instructions given by adults.

2. Wear eye protection and ensure children are at a safe distance for the demonstration.

National Curriculum Requirements

For a full list of National Requirements covered, please see the Scheme of Work.

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 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.


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Learning Outcomes

All children should

Collect data from their own observations and measurements. Know that everything is made of tiny particles called atoms and molecules, and

because these particles are small, scientists use models to represent them. Know that solid, liquid and gas particles move at different rates. Be able to draw a particle diagram for a solid, liquid and a gas. Identify problems with an experimental design.

Some children could

Collect data from their own observations and measurements, using notes, simple tables and standard units.

Understand that liquids turn to gases by evaporation and diffuse away into the atmosphere.

Pupils could be given a worksheet showing the various melting points and boiling points of the elements and have to identify the state of matter in which they exist at room temperature.

A few children could

Collect data from their own observations and measurements, using notes, simple tables and standard units, and help to make decisions about how to record and analyse this data.

Suggest ways to improve the experiment to obtain more meaningful results.

Suggest ways in which the experiment could be of use. Learn what Particle Theory is and how it is used to explain chemical and physical

phenomena. Use a particle diagram to explain how to make a cup of tea ‘stronger’. Research the 1986 Lake Nyos disaster.

Introductory Activity

Discuss with the class what they understand by the terms ‘Evaporation’ and ‘Condensation’ and explain the difference between them. From this discussion explain that evaporation is the process where a liquid turns into a gas, and condensation is where a gas turns into a liquid. These processes are temperature dependent so you may want to explain the term ‘boiling point’. See if they can think of any everyday examples. Eg. Boiling a kettle, the mirror after a shower etc. You could also discuss the concepts of freezing and melting and introduce pupils to melting points.

Begin with a discussion on solids, liquids and gases. Use everyday examples for children to sort into the three categories. Explain that all matter can be classed as one of the three states, but some can change from one to another. Can pupils think of examples? What causes the change? Show children a diagram of particles. Children love to become “particles”, so a drama activity in the hall would be a useful exercise to embed the idea.


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Teacher Demonstration

Demonstration 1.1 – Whoosh Bottle

You will need: safety screen, whoosh bottle, methylated spirits, measuring cylinder, wooden splint, metre stick, blu tack.

The reaction vessel container used is a water cooler bottle (made of polycarbonate). A clean, completely dry bottle is required for each demonstration. It takes time to clean and dry once it has been used for a demonstration.

Select a safe, level place for the demonstration, with at least 2.5 metres clearance above the top of the vessel to the ceiling above, and no flammable materials above it.

Attach a wooden splint at a right angle to the end of the metre rule or stick using blu tack. Provide a lighter or matches well away from the alcohol bottles.

Students should be standing at least four metres away, behind the safety screen. Refer to the video for visual instructions if required.

HEALTH & SAFETY: The demonstrator should wear eye protection.

1. Pour about 40 ml of the alcohol (Methylated spirits) into a beaker and then transfer into the reaction vessel. Ensure that the alcohol bottle is re-stoppered directly after pouring out the 40ml and placed well away from the demonstration area. 2. Roll the water bottle on its side for thirty seconds, to and fro quite vigorously, allowing the alcohol to vaporise and the vapour to fill the vessel. Do not warm the alcohol to aid evaporation. 3. Pour ‘all’ surplus liquid alcohol back into the beaker, draining the vessel as completely as possible, and move the beaker back to the rest of the alcohol stock, away from any risk of catching fire. Surplus liquid left in the vessel may ignite and set fire to the vessel as well. 4. Stand the water bottle securely inside the safety screens and remove the stopper. Light the wooden splint, and apply the lighted end of the splint to the open neck of the vessel. Do not lean over the screens to apply the ignition. Do not ignite by dropping a lighted match into the vessel. 5. The alcohol vapour should ignite with a loud ‘whoosh’, with flames shooting out of the top of the vessel. 6. The reaction can only be repeated once the reaction vessel has been completed purged of CO2 by completely filling with water and then pouring this out, draining and leaving to dry.

Possible Questions/ Suggestions for discussion

What did you see? Smell? Hear? Feel?

Using your knowledge, what happened to the liquid inside the container?

What ideas can we come up with as to why the flame came out of the bottle?

What happened to the particles inside the bottle before/after the lighted splint was added?

Children’s Investigation

Investigation 2.1 – Diffusion of Oils

Pairs will need: petri dish, stop watch, metre stick, scented oil

Demonstrate the apparatus that the students will be using and depending on the class either show or give them some written or verbal instructions on how to carry out the investigation. It should be noted that in this experiment, the variables are almost impossible to control. This makes it almost impossible to obtain valid, precise and accurate data. Pupils will almost certainly be able to suggest ways in which to improve this experiment. The main objective here is to allow pupils to practise recording data and analysing it. The data will be very variable and this gives an excellent opportunity for students to look at data from which no meaningful conclusion can be drawn. (Even though they will usually always try to infer some clear result!)

1. Working in pairs. One child holds a stopwatch. 2. They move 1m away from their partner. 3. The second child drops two drops of oil/perfume onto a petri dish and holds it in front of them. 4. The child with the stopwatch then starts timing, until they can smell the oil/perfume. 5. Together, they record the time/liquid. 6. Repeat with another oil/perfume.


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Did you find any problems in carrying out your investigation? How valuable are your results? How many variables could you name? How did the smell travel from the petri dish to your nose? Does the cost of a perfume or aftershave determine how quickly it diffuses? What might affect how quickly a vapour / gas particles travel? How could we make this a fair test which produces valid data?

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

1. Ask the class what they learnt / discovered…providing the wherewithal so that children can say

‘I used to think ......... and now I think.......... because ......’ or

‘I used to think ......... and I still think .......... because ......’

2. Through whole class discussion elicit from the pupils what they observed. 3. What do children think they needed to do to ensure that they would get the same results if they or

someone else was to repeat this experiment? 4. The class should write on their experiment sheets an agreed definition for the term ‘valid data’. 5. There might be an opportunity during the lesson to discuss what kind of graph would be best used to

display data from this kind of experiment. 6. How could this experiment be improved to make the data more precise, accurate and valid? 7. In what ways might data from this type of experiment be useful in the real world? (Manufacture of

perfumes / aftershaves / understanding how fast a toxic gas leak might move). It is worth mentioning that the perfume industry alone is worth over £15 Billion each year! So being good at experimental design in this area of science offers a potentially lucrative career!)

Cross curricular links

Literacy

Writing instructions for the demonstration/investigation using imperative verbs. Definitions of scientific vocabulary as part of a class science dictionary/glossary. Use a dictionary to check the meanings of words read. Use scientific vocabulary to develop descriptive writing e.g., verbs and adverbs to

describe the movement of gases.

Numeracy Discussion and use of a variety of tables, diagrams.

Other subjects

Research the Lake Nyos disaster, when on August 21, 1986, an eruption occurred which triggered the sudden release of about 100,000 - 300,000 tonnes (some other sources state as much as 1.6 million tons) of CO2.

Research Thomas Graham or James Clerk Maxwell, both Victorian scientists, and their work leading to our understanding of diffusion.

Robert Boyle is largely regarded today as the first modern chemist, and therefore one of the founders of modern chemistry, and one of the pioneers of modern experimental scientific method. He is best known for Boyle's law.

Useful websites

Type these links

How diffusion works video Lake Nyos Disaster BBC Bitesize Particle Model A video showing diffusion in action

bit.ly/how-diffusion-works bit.ly/Lake-Nyos bit.ly/Bitesize-particle-model bit.ly/diffusion-video

http://bit.ly/how-diffusion-works

http://bit.ly/Lake-Nyos

http://bit.ly/Bitesize-particle-model

http://bit.ly/diffusion-video


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Lessons 3 & 4: Solids, Liquids & Gases


1. Build on knowledge of different materials and their properties. Use the diagrams/drama to explain how the particles in solids, liquids and gases are joined and move.

2. Moving particles have energy. When they stop moving, they release energy, in the case of the crystals, this is in the form of heat. This is called an exothermic reaction.

Sodium Ethanoate Stalagmite When the solution cools it becomes supersaturated. This means that more of the sodium acetate is dissolved than would be possible under normal conditions. Any kind of shock to the flask will cause the sodium ethanoate to recrystallise. When it is poured onto the seed crystals, it cools and so recrystallises forming the stalagmite.

3. The properties of silly putty are unusual due to the ingredient polydimethylsiloxane (PDMS). This is a viscoelastic liquid silicone, which makes it act as a viscous liquid over a long time, but as an elastic solid over a short time. This explains why it flows like a liquid, but can bounce or break like a solid. As well as being used in toys, the material is used by physiotherapists for rehabilitative therapy of hand injuries. Apollo astronauts also used it to secure their tools in zero-gravity because of its adhesive characteristics.

Silly Putty The silly putty has a property known as viscoelasticity. This means that over time it will flow slowly but it also has the property that it can bounce like a ball.


Materials can only have properties of one state of matter. Particles of solids have no motion, all particles (in solids, liquids, and gases) move because they have kinetic

energy. Particles in solids vibrate about fixed sites. The vibrations are so small we can’t see them. Particles possess the same properties as the materials they compose. For example, atoms of copper are “orange

and shiny”, gas molecules are transparent, and solid molecules are hard. Pliable solids (such as clay) are not solid.







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 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.


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Learning Outcomes

All children should

Collect data from their own observations and measurements. Record evidence in a scientific way. Evaluate their own theories in light of their evidence. Recall that everything is made of tiny particles called atoms and molecules, and

because these particles are small scientists use models to represent them. Learn that materials are classified in terms of properties of solids, liquids and gases. Generate descriptions of these properties using their knowledge and observations

and learn that some materials are difficult to classify.

Some children could

Specifically identify the best way to record data. Collect data from their own observations and measurements, using notes, simple

tables and standard units. Extend a scientific model to explain every day phenomena. Suggest ways in which the experiment could be of use. Research the life of Democritus - who first used the word Atom – which means that

which cannot be divided and conduct his simple but elegant thought experiment using a piece of paper to see how small a piece you can get by cutting it in half continually.


Collect data from their own observations and measurements, using notes, simple tables and standard units, and help to make decisions about how to record and analyse this data.

Suggest ways to improve the experiment to obtain more meaningful results. Explain in detail, using particle theory, why some substances that appear to be solid

are in fact liquids. Explaining phenomena such as sublimation E.g. in substances like solid air fresheners

or solid CO2. Research non-Newtonian fluids. Design an experiment to see if there are any other ‘powders’ that work as non-

newtonian liquids. Very keen students who perhaps have heard of ‘Plasma’ from various space films etc.

could produce a report on the difference between a plasma and a gas (plus diagrams!)


Pupils should be able to give some examples of solids liquids and gases and explain that these states of matter are inter-changeable depending on the temperature of the material. Ask students if they have ever used a rechargeable hand warmer such as those which contain a colourless liquid which turns into a white solid when a metal disc is clicked. Demonstrate one and pass some around for students to feel. • Demonstrate that the hand warmer can be ‘recharged’ by heating it in boiling water. • Challenge students to explain what is happening in this situation. You might also like to link this activity to the energy changes in reversible processes. Remind children of the particles of materials. Extend this by discussing other ways in which we classify things into solids, liquids or gases:

Use examples: If I poured sand into a bottle, what would happen? If I poured water into a bottle, what would happen? If I poured marbles into a bottle what would happen?


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Demonstration 3.1 – Sodium Ethanoate Stalagmite

You will need: gas cartridge and burner, tripod and leg extensions, matches, heatproof mat, gauze, sodium ethoanoate, water, petri dish, conical flask/beaker, stirring rod

1. Weigh 125 g of hydrated sodium ethanoate into the beaker and add 12.5 ml of water. 2. Heat the beaker over a low flame and stir until the solution clears completely. 3. Cover the beaker with a paper towel and allow it to cool to room temperature to give a supersaturated solution. (Steps 1-3 Should be done ahead of time, even the day before to allow time to cool) If the solution is knocked, the reaction will take place prematurely. If this happens, you will need to reheat the solution. 4. Remove the paper towel and place a few crystals of sodium ethanoate on it. 5. Pour the supersaturated solution slowly onto the sodium ethanoate crystals. The solution should crystallise immediately on contact with the crystals. It will form a growing ‘stalagmite’ of solid sodium ethanoate as more and more of the solution is poured onto it.

Demonstration 3.2 - Smart Putty

You will need: tripod, smart putty, cd

1. Place a CD on a tripod with the hole centred. 2. Put some silly putty into the hole. 3. Measure the distance from the desk to the silly putty every 5 minutes.

Please see links below for more information (and a little fun!) Lesson notes for the sodium ethanoate stalagmite. bit.ly/sodium-ethanoate-stalagmite Measuring the stalagmite temperature video. bit.ly/measuring-stalagmite-temperature Some fun between two putty characters. bit.ly/putty-characters


Children watch the solution solidify instantly turning to a solid. They may have experience of small crystal sets at home, but this is better and presents a good opportunity to differentiate between liquids and solids. Were they surprised at how little water was used? Where have they seen this reaction before? (Frozen?)

You could ask students to grow their own crystals from different salts by tying a seed crystal to a length of cotton thread or very fine fishing line and suspending it in a saturated solution. Good crystals can be obtained from aluminium potassium sulphate (alum), magnesium sulphate, and iron (II) sulphate.

In addition, children will handle silly putty, watching the putty change over time and drawing on their knowledge to observe and question and explain this interesting phenomena. Is it a solid or a liquid? Why?


Investigation 4.1 – Thixotropic (non-Newtonian) Substance

Pairs will need: 1 x Washing up bowl, cornflour/custard powder, water, food colouring

This investigation is a lot of fun, very messy and provides an excellent opportunity for pupils to apply a scientific model and follow instructions very carefully. Food colouring can be added for an even greater effect.

Method: (With sleeves rolled up!) 1.Measure about three tablespoons of the cornflour or custard powder into the plastic bowls 2. Carefully add water, ½ teaspoon at a time, and mix until it can be picked up as a semi crumbly ball and rolled in the hand. 3. With care, add ‘drops’ of water as the pupil applies a little pressure whilst rolling it around between their palms. 4. If the pupil then quickly opens their hands and holds the ball in their palm it should ‘magically’ turn to liquid! Children can record the volume of water needed to make the thixotropic substance, then use this data to compare with other groups.

http://bit.ly/sodium-ethanoate-stalagmite

http://bit.ly/measuring-stalagmite-temperature

http://bit.ly/putty-characters


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Investigation 4.2 – Materials Circus

You will need: Sand (50g pot), jelly powder made into jelly, talcum powder, tomato sauce sachet, blu tack, density block set (foam, wood, glass, brass, aluminium), petri dish labelled oxygen, nitrogen

Use of a ‘circus of activities’, and in this case the materials circus, is an excellent way to allow pupils to repeatedly apply recent learning through hands on observation and discussion in pairs and groups. Pupils also have to move around the classroom in stages which is a good way of breaking the potential monotony of static seated lessons.

The investigation used here is very simple but allows pupils to develop the skill of making rapid observations whilst adjusting quantities of substances used with some real precision to detect changes in the properties of the substance.

Demonstrate the apparatus that the students will be using and depending on the class either show or give them some written or verbal instructions on how to carry out the investigation circus.

The different materials should be set up around the class in different containers where necessary and the pupils asked to walk around in pairs or threes to study the materials: -

Naming them. Determining whether they are solids, liquids or gases.

Explaining why they have come to the conclusions they have using verbal, written or graphical explanations and by using particle model diagrams.


Get the class to record their observations and classifications of each material. Once the mess has been cleared away (this should only take a few weeks!) have a short class discussion for pupils to try to explain what they saw using the ‘particle model’.

Was the thixotropic substance a solid, liquid or a gas? What caused the change? Which other materials can change state? Ask the class if they can work out where clouds come from using particle theory. Ask the class to explain why clothes on a washing line dry. As a high level extension question, you might like to ask if they can think about how water changes from a

vapour into a solid when it snows using the concept of particles and energy flows.


Ask the class what they learnt / discovered…providing the wherewithal so that children can say ‘I used to think ......... and now I think.......... because ......’ or


Share decisions on classification of materials, and encourage children to debate their findings. Through whole class discussion elicit from the pupils what they observed during the investigation. Suggest ways in which to record their findings, and go on to present their data in a scientific way. What do children think they needed to do to ensure that they would get the same results if they or someone

else was to repeat this experiment? The class should write on their experiment sheets an agreed definition for the term ‘valid data’. There might be an opportunity during the lesson to discuss what kind of graph would be best used to display

data from this kind of experiment.


Literacy Writing instructions for the demonstration/investigation using imperative verbs. Definitions of scientific vocabulary as part of a class science dictionary/glossary. Creative writing around the “magic potion/slime” created.

Numeracy

Discussion and use of a variety of tables, diagrams. Some understanding of large numbers when describing how small atoms and molecules

are and expressing these possibly as factors and powers e.g. 1 x 106. Developing accurate measuring skills. Improve language related to ration and proportion.


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Other subjects

Research Sir Isaac Newton, particularly his time spent working at the Royal Mint, when he notoriously chased down counterfeiters ensuring they were hung, drawn and quartered!

Meet the Greek philosopher, Democritus. We love this guy because he's the father of the Particle Theory. This is crazy to think about, but over 2,400 years ago Democritus was sitting around Greece thinking about matter, which is anything that has mass and takes up volume.

Useful websites

Shortened web links (Type these)

BBC Bitesize solids, liquids and gases. BBC Bitesize particle model animation. Wikipedia on property of silly putty. Watch custard dancing on a loudspeaker. Watch custard dancing on a loudspeaker in slow motion. Wikipedia entry on Democritus.

bit.ly/solids-liquids-gases bit.ly/particle-model-animation bit.ly/viscoelasticity bit.ly/custard-on-loudspeaker bit.ly/slo-mo-custard-on-speaker bit.ly/Democritus-wiki

http://bit.ly/solids-liquids-gases

http://bit.ly/particle-model-animation

http://bit.ly/viscoelasticity

http://bit.ly/custard-on-loudspeaker

http://bit.ly/slo-mo-custard-on-speaker

http://bit.ly/Democritus-wiki


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Lessons 5 & 6: Introduction to Chemical Reactions (1)


1. The simple description of a chemical reaction is the rearrangement of atoms in starting substances called REACTANTS to produce end substances called PRODUCTS. This definition can be used to describe simple everyday examples. Chemical reactions can be spontaneous, or non-spontaneous. A slightly more complex definition is that chemical reactions involve the movement of electrons in the forming and breaking of chemical bonds. Children will just need to know that a chemical reaction has occurred – they will know that because there has been a change in colour, size, shape etc. or light, smell, heat etc. was created. 2. Elephants toothpaste explained: The potassium iodide is a catalyst which makes the hydrogen peroxide break down very quickly into oxygen and water. Hydrogen peroxide (H2O2) decomposes into water and oxygen gas, but normally the reaction is too slow to be easily perceived or measured. 2H2O2 → 2H2O(l) + O2(g) There is a lot of oxygen trapped in peroxide, so this rapid reaction gives out a large volume of oxygen. The soap mixed with water turn into foam as the oxygen bubbles foam. The oxygen gushing out is what makes the soap bubbles move. Acids react with most metals and a salt + hydrogen is produced. The general word equation for the reaction: metal + acid → salt + hydrogen It doesn’t matter which metal or acid is used, if there is a reaction we always get hydrogen gas as well as the salt.


Acids are active agents that damage skin and other materials. The idea develops in young children, who learn to think of acids as “dangerous”. Cartoons showing scientists making holes in benches with acids also contribute to this image. Acids are not perceived as being particulate, but rather continuous matter with special properties.

Metals are eaten up by acids and simply vanish. All gases behave in the same way. All chemical reactions produce a gas An observed ‘fizz’ is not associated with the release of a gas in a solution.



1. Ensure children are aware of the rules of science: d) Regular hand washing. e) Nothing is to be put in their mouths or eyes. f) Follow instructions given by adults.

2. Wear eye protection and ensure children are at a safe distance for the demonstration. 3. Ensure children do not touch the foam from the Elephant’s Toothpaste, although they

may be allowed to feel the heat lost through the measuring cylinder. 4. Please refer to the Risk Assessment sheet for this investigation and demonstration

(hydrochloric acid, sulfuric acid, nitric acid, ethanoic acid, hydrogen peroxide, potassium iodide solution).

5. The contents of all of the test tubes should be placed into a sieve in a sink. The acids may be washed down the drain with plenty of water with small quantities of residual metals simply disposed of in the main school waste receptacle.




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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 the data obtained from the experiment and determining whether or not it proves or disproves the


Learning Outcomes

All children should

Record scientific observations and developing explanations. Measure accurately and understand the need for safe practice when carrying out

investigations. Use graphs to display data recorded. Learn that carbon dioxide is a dense gas and ‘suffocates’ flame which is why it is used in

fire extinguishers.

Some children could

Suggest ways to record data. Learn the test for oxygen – relights a glowing splint. Develop the skill of applying particle theory to explaining simple chemical reactions. Learn that chemical reactions are often associated with release of a gas, change in state

and change in temperature. Potentially research an experiment of their choice in which they are to state clearly

what observations they are looking for, the equipment they intend to use and critically how they would ensure their data was valid. The following website is quite a good starting point for pupils. bit.ly/easy-science-experiments


State clearly that their results are valid because of the various factors they controlled. Suggest ways to improve the experiment to obtain more meaningful results. Learn the simple description of a chemical reaction as REACTANTS reacting to produce

PRODUCTS and use this to describe simple every day examples. Learn that metals react with acids to produce hydrogen gas. Learn the squeaky pop test for hydrogen. Explain how to ensure data from a range of other experiments is valid.


What gases do children know, and what are their uses? Discuss the fact that air is not a gas, but is made up of many gases – nitrogen, oxygen, carbon dioxide, argon, plus a variety of rare gases. Use of Science Demonstration: Elephants Toothpaste A fun demonstration which will amaze the children as the reaction occurs very quickly with lots of foam emerging quickly from the reaction vessel clearly. The reaction provides learners with a clear visual stimulus and a wow factor to provoke questions linked to their knowledge.

http://bit.ly/easy-science-experiments

http://bit.ly/easy-science-experiments


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Demonstration 5.1 – Elephant’s Toothpaste

You will need: 1l measuring cylinder, washing up bowl, bin bag, washing up liquid, splint, matches, hydrogen peroxide, potassium oxide, food colouring, 50ml measuring cylinder

Wear safety glasses 1. Place 20 ml of the 30% hydrogen peroxide into the large measuring cylinder. Place the cylinder into a washing up

bowl, on an open black bin bag.

2. Add about 5 ml of washing up liquid to the cylinder.

3. Add a few drops of food colouring.

4. Finally, add 1 heaped spatula of potassium iodide powder. The reaction takes place quickly, so it is important to

stand back.

5. You will notice that the foam has a brown tint. This is due to the presence of free iodine produced by the extreme

oxidizing power of the 30% hydrogen peroxide.

6. Quickly light a splint, when the flame has caught, gently blow the flame out and insert the glowing splint into the

foam. The splint should relight. This is the test for oxygen, the oxygen relights the splint.

Demonstration 5.2 – Carbon Dioxide Trough

You will need: CO2 trough, 5l jug, 4 tea lights, matches, vinegar, sodium bicarbonate

1. Set up the trough and light the tea lights. 2. Darken the room a little. 3. Place a few table spoons of sodium hydrogen carbonate (NaHCO3) into the plastic jug. 4. Add about 50 – 70 ml of vinegar/ethanoic acid (CH3COOH) to the jug. 5. Immediately after the reaction has subsided, pour the carbon dioxide gas (NOT the liquid) with a flourish into the top of the trough. Please see links below for more information (and a little fun!). Steve Spangler’s video of different strengths hydrogen peroxide. bit.ly/elephants-toothpaste Another way of showing carbon dioxide putting out candles. bit.ly/candletastic


Why did the splint relight?

Why is there so much foam?

Why did the candles go out?

Why did the candles go out in order from top to bottom?

What differences are there between oxygen and carbon dioxide?


Demonstration 6 .1 – Metals and Acids

Pairs will need: 1 x test tube rack, 4 x test tubes, selection of metals, selection of acids, 1 x tweezer, 4 x pipettes

Children use a range of acids in order to observe the effect they have on metals. This investigation encourages the independent use of a range of equipment with skill and precision, and creates the opportunity to collect lots of good data rapidly. This can then be used to compare with their friends and present their data in a range of ways from graphs to charts and videos etc. 1. Instruct the students to measure out about 3 ml of HCl (hydrochloric acid) into 4 test tubes.

2. Pupils should then place a few pieces of a different metal into each test tube one by one and record their

observations. Pupils could draw, write or photograph what happens in each tube.

3. Clean out the test- tubes by pouring the contents into a sieve in the sink and rinsing.

4. Repeat steps 1 – 3 with the other acids – Sulphuric, Nitric, Ethanoic.

5. Students can test each of the test tubes for hydrogen gas by holding their thumbs over the ends tightly for a few

seconds and then inserting a lit splint (not into the acid!). This should generate a pleasant little ‘squeaky’ pop.

6. When finished, ask the pupils to empty their test tubes into a sieve in the sink or plastic basin and wash their

hands.

http://bit.ly/elephants-toothpaste

http://bit.ly/candletastic


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• Metals react with acids to produce hydrogen gas. • There are often ‘patterns’ in science and these are important for making scientific predictions to test. • VALID data is obtained from experiments where only one variable is changed.

1. Is there a pattern to your observations? How can you tell? 2. Do you think all metals and acids react the same way? 3. How can the data from this experiment be ‘Valid’ 4. How could you investigate your theory / observations further?





Discuss what children have observed and identify any patterns or unusual results. What existing knowledge do they have to explain what they have seen? What have they learnt from this investigation? Discuss with the class what they think they needed to do to ensure that they would get the same results if they

or someone else was to repeat this experiment. This could include mention of types of metals used, shape, size and surface area of metals, types of acids and their strengths and temperatures.

There might be opportunity during class to discuss what kind of graph would be best used to display data from this kind of experiment.


Literacy

Creative writing inspired by the Elephants toothpaste e.g. Disaster Strikes at the local zoo … news headlines/interviews

Poetry from the flowing motion of the liquid.

Diary of a famous scientist (the day they used too much acid!!!) Practise using this vocabulary for reading exercises for homework / producing a

scientific report: Independent and dependent variables, particles, atoms, molecules, iron (Fe), copper

(Cu), magnesium (Mg), zinc (Zn) hydrochloric acid (HCl), sulphuric acid (H2SO4), nitric

acid (HNO3), ethanoic acid (CH3COOH), chemical reaction, fizzing, rate, rate of flow.

Numeracy Practise using different graphs to represent scientific observations – bar charts, pie charts,

pictographs.

Other subjects

Fables – The Story of Pliny the Elder, and the discovery of aluminium Research into where metals come from, and whether any will be discovered on other

planets. Will we be mining on the moon one day? With his long hair, his beard, and his passion for chemistry, Dmitri Mendeleev was a

charismatic professor. He had his beard cut once a year. His greatest discovery was of the periodic law and his creation of the periodic table –after falling asleep in front of cards on which he’d written the names of the 65 then known elements.


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Useful websites


BBC Bitesize on metal and acids. Video comparing water and hydrochloric acid with metals. Dramatic video comparing coke cans reacting in hydrochloric acid and sodium hydroxide. BBC Bitesize on physical and chemical changes. Metal spoon reacting with water! Very visually interesting reaction between Copper and concentrated Nitric acid. Don’t be put off by the chemistry explained in the video – it’s simply very interesting for pupils to watch. Copper penny in nitric acid – see the introduction in the scheme of work. The link below is a little more advanced, but will be useful for pupils who are more interested and wish to take the topic a little further. Contains useful little animations on states of mater.

bit.ly/acids-metals bit.ly/acid-metal-water bit.ly/coke-can-acid bit.ly/chemical-reactions bit.ly/dissolving-metal-spoon bit.ly/copper-nitric-acid bit.ly/copper-penny-nitric-acid bit.ly/ACS-Chemistry

http://bit.ly/acids-metals

http://bit.ly/acid-metal-water

http://bit.ly/coke-can-acid

http://bit.ly/chemical-reactions

http://bit.ly/dissolving-metal-spoon

http://bit.ly/copper-nitric-acid

http://bit.ly/copper-penny-nitric-acid

http://bit.ly/ACS-Chemistry


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1. All chemical reactions involve a change in energy. Sometimes the change that occurs is so small that it is not detected, but often this change results in an increase or a decrease in the temperature of the system.

2. In chemical reactions, bonds are broken and new bonds are formed. Energy must be added to break the bonds that hold atoms of the reactant together. Likewise, when bonds are formed to make a product, energy is released. If the amount of energy released when the product forms is greater than the amount of energy required to break the bonds of the reactant, energy will be released. However, if the amount required to break bonds is more than the amount released when new bonds form, energy must be taken in from the environment (endothermic). Reactions which release energy are called exothermic reactions. In an exothermic reaction, the energy of the reactants is greater than that of the products. The difference in energy is the amount of energy (usually transferred via heat) that flows from the reaction to the surroundings causing the temperature to increase.


“Errors, like straws, upon the surface flow; He who would search for pearls must dive below.”- John Dryden

From Chemistry in Education

Energy changes in chemistry can appear to be very familiar and straightforward, but this familiarity can lead to some strongly held misconceptions that are very persistent and difficult to change.

One problem is that we can’t ‘see’ energy. We can only sense and measure the effect it has when it is transferred between system and surroundings.

According to the first law of thermodynamics energy cannot be created or destroyed. Research, however, shows that many students believe that energy is produced or used up during chemical reactions.

This view may arise because students’ early ideas about energy change are strongly influenced by examples of

combustion. They see that energy appears to be created by burning fuels and that this energy runs out when the

fuel is ‘used up’. This misconception is reinforced by words they hear and use in everyday language. They hear

about the need for ‘energy generation’ and they know that they have to keep recharging their mobile phone. All of

this makes learning that energy is transferred rather than created or destroyed in chemical reactions more difficult.

Change is at the heart of chemistry and in order to develop an understanding of chemical ideas learners need to experience the large numbers of examples of chemical change in everyday life, not just those in science laboratories.

It is often not possible to decide definitely whether a particular change can be categorised as chemical or physical

(Many everyday changes that take place during cooking, living, dying or making tea are very complicated and often

consist of lots of different changes, some of which may be chemical and some physical!)

Identifying endothermic and exothermic processes. If energy flows out of the reaction and raises the temperature of the surroundings, the reaction is exothermic. If energy flows into the reaction causing the surroundings’ temperature to decrease, the reaction is endothermic.

Using the phrase “energy is stored in chemicals” leads to the belief that if the bonds are broken the energy will be released. However, energy is released to the surroundings only when a chemical reaction occurs in which the energy that is released in forming the products is greater than the energy needed to break the bonds in the reactants. For example, it is the chemical reaction of fossil fuels with oxygen that results in the release of energy.




2. Wear eye protection and wash hands after placing in the solution created during the demonstration.


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3. Please refer to the Risk Assessment sheet for this investigation and demonstration

(sodium hydroxide, hydrochloric acid, citric acid, copper(II) sulphate solution and

sulphuric acid).

4. Ensure children are wearing eye protection and gloves during the investigation.






Learning Outcomes

All children should

Practise safe chemical handling skills. Suggest ways to present results in a scientific manner. Measure temperature changes accurately using a thermometer. Learn that chemical reactions often involve a change in temperature. Learn that if the temperature goes up the reaction is EXOTHERMIC and if the

temperature goes down it is ENDOTHERMIC.

Some children could

Be able to explain why their data was reliable or not. Decide upon the best way to present their results. Be able to state and explain a range of exothermic and endothermic reactions. Identify reactions as endothermic or exothermic. Record simple word equations.


Make accurate judgements about the accuracy and reliability of experimental data. Begin to use symbols: O2 H2 N2 CO2 CO Cl2 O3 Pupils could be asked to buy a variety of ‘fizzy’ sweets that have different chemicals in

them and find out which ones cause the greatest drop in temperature in a controlled volume of water. (Fizzy ‘sherbets’ have a range of different acids from citric, malic and tartaric acid with different ‘bases’ from sodium bicarbonate, sodium hydrogen and magnesium carbonate all of which will give different temperature changes in water depending on the ratio of different chemicals in each and the quantity used).

Research the coldest and hottest chemical reactions and create a small presentation on each.

Research uses of endothermic and exothermic reactions in medicine, cooking, engineering, research.


Discuss with the children beforehand about energy in reactions to prepare them for this practical. Also ensure they know how to measure temperature precisely and accurately.


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Demonstration 7.1 – Foaming endothermic reaction

You will need: Sodium Hydrogen carbonate, citric acid, 2l jug, food colouring, water, washing up bowl, black plastic bag

1. Place about 200 ml of the sodium hydrogen carbonate and 100 ml of the citric acid into the 2l plastic jug. 2. Add a little food colouring and give the dry mixture a really thorough mix by simply swirling the mix around for a few moments. 3. Stand the beaker in a washing up bowl in an open black bag and ask the students to roll their sleeves up. 4. As the reaction takes place very quickly you will need to ensure that those students who wish to participate are close at hand. 5. From another large plastic beaker /basin quickly pour about one litre of water into the powder, the reaction is instantaneous and students can stick their hands in it! HEALTH & SAFETY: The demonstrator and pupils should wear eye protection and rinse hands after placing in the solution. Please see link below for a smaller scale version of the experiment. bit.ly/endothermic-reaction-at-home


The reaction releases a large volume of carbon dioxide gas (about 12 Litres of gas for each 100 grams of citric acid!). The reaction is endothermic, taking heat in form the surroundings and so the foam feels cold to the touch.

Which previous demonstrations or investigations can children see links with?

What do they already know about chemical reactions?

What did they feel?

Why could that have happened?

This could be written as either: Citric acid + Sodium hydrogen carbonate Sodium citrate + Carbon dioxide + Water Or: C6H8O7 + 3NaHCO3 C6H5O7Na3 + 3CO2 + 3H2O


Investigation 8.1 – Endothermic and Exothermic reactions

Pairs will need: 1 x EPS cups, 1 x tripour beaker, 1 x 100ml measuring cylinder, sodium hydroxide, hydrochloric acid, thermometer, water, spatula, citric acid, copper(II) sulphate solution and magnesium chips, sulphuric acid and magnesium ribbon, sodium bicarbonate

A paired activity in which learners get to carry out tests on a range of chemicals, and feel like ‘real scientists’, in order to generate a range of observations and data to share with other groups. If working with younger children, you may wish to choose from these investigations, older children may manage all of them. Alternatively, groups could carry out a similar investigation and compare results. The EPS (polystyrene) cup is placed in a tripour to reduce the risk of it tipping over and spilling chemicals on the tables. Pupils should carry out each of the following reactions ensuring that all temperature measurements are accurately recorded. Procedure: Pupils must wear eye protection and gloves throughout. This experiment should be carried out in pairs with pupils supported by the classroom teacher and teaching assistants where possible. There should not be more than two groups of pupils per table. Reaction of sodium hydroxide solution and dilute hydrochloric acid 1. Stand the polystyrene cup in the beaker. 2. Use the measuring cylinder to measure out 10 ml of sodium hydroxide solution and pour it into the polystyrene cup. 3. Measure the initial temperature of the sodium hydroxide solution and record it in a suitable table. 4. Measure out 10 ml of hydrochloric acid and carefully add this to the sodium hydroxide solution in the polystyrene cup. Stir with the thermometer and record the maximum or minimum temperature reached. 5. Work out the temperature change and decide if the reaction is exothermic or endothermic. 6. Discard the mixture (in the sink with plenty of water). Rinse out and dry the polystyrene cup.

http://bit.ly/endothermic-reaction-at-home


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Reaction of sodium bicarbonate solution and citric acid 1 Repeat steps a – c of the previous experiment, using sodium bicarbonate solution in place of sodium hydroxide solution. This is made simply by dissolving adding 4 heaped spatulas of the sodium bicarbonate powder in 10ml of water in the polystyrene cup. 2. Add four small (not heaped) spatula measures of citric acid. Stir with the thermometer and record the maximum or minimum temperature reached. 3. Work out the temperature change and decide if the reaction is exothermic or endothermic. 4. Discard the mixture (in the sink with plenty of water). Rinse out and dry the polystyrene cup. Reaction of copper(II) sulphate solution and magnesium chips 1. Repeat steps a – c of the first experiment, using copper (II) sulphate solution in place of sodium hydroxide solution. 2. Add one small (not heaped) spatula measure of magnesium chips. Stir with the thermometer and record the maximum or minimum temperature. 3. Work out the temperature change and decide if the reaction is exothermic or endothermic. 4. Discard the mixture into a sieve (in the sink with plenty of water). Rinse out and dry the polystyrene cup. Reaction of sulphuric acid and magnesium ribbon 1. Repeat steps a – c of the first experiment, using sulphuric acid in place of sodium hydroxide solution. 2. Add one three centimetre piece of magnesium ribbon. Stir with the thermometer and record the maximum or minimum temperature reached. 3. Work out the temperature change and decide if the reaction is exothermic or endothermic. 4. Once all the magnesium ribbon has reacted, discard the mixture into a sieve (in the sink with plenty of water). Throw away the polystyrene cup.


What did you see? Were all reactions the same? Why would that be? Are there any patterns in the results collected? Ask pupils to give examples of every day exothermic and endothermic reactions (whilst the sun is technically a

thermonuclear reaction, any pupil saying the sun is hot due to an exothermic reaction is correct) Remind pupils of the reaction making the sodium ethanoate stalagmite – energy was used to dissolve the

solute and this energy is released when the solution crystallizes which is why it gets hot. What would be the best way to record results? There are different ways to analyse the data. Pupils could enter their data onto the IWB after recording their

data on paper.





Tabulate results in groups or as a class. Use this to compare, identify patterns and any unusual results. Can children use their findings to explain uses of different metals or acids in real life situations? How do results match predictions? Explain reasons for, or for not, supporting their predictions. How could this experiment be improved to make the data more precise accurate and valid? Pupils could then work in small groups to try and make sense of the data, identifying anomalous results and

judging the overall reliability of the data. Alternatively, you could use a selection of the students’ data on the IWB to initiate a class discussion on what the data really shows and discussing the overall reliability.


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Literacy

Pupils can produce a scientific report including conclusions. Provide opportunity for pupils to use this vocabulary in class and in reading exercises

for homework. Extensive creative writing opportunities using the foaming endothermic reaction

demonstration.

Numeracy Accurately recording temperature data using the Celsius scale 1.0 decimal places,

comparing data and commenting on its accuracy and precision.

Other subjects Red cabbage acid indicator artwork. bit.ly/red-cabbage-artwork

Useful websites


BBC Bitesize demonstrations. How to make bags full of oxygen & carbon dioxide.

Curious and colourful chemical reactions.

bit.ly/endothermic-exothermic-demonstrations bit.ly/make-oxygen-carbon-dioxide bit.ly/curious-chemical-reactions

http://bit.ly/red-cabbage-artwork

http://bit.ly/endothermic-exothermic-demonstrations

http://bit.ly/make-oxygen-carbon-dioxide

http://bit.ly/curious-chemical-reactions


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1. Reactions don’t happen unless the substances are in contact. The particles of the materials need to get together so that they can react. Reactions only happen if the particles have enough energy. The minimum amount of energy needed to start a reaction is called the Activation Energy. The amount of activation energy needed is different for each reaction. Every reaction has activation energy; they all need a little push to get started.

2. The collision theory: (Proposed by Max Trautz and William Lewis in 1916 and 1918) Particles are constantly moving. For a chemical reaction to take place the reactant particles must collide first. For the collision to be effective the particles must have the right amount of energy. Factors affecting the rate are the temperature, concentration, and pressure of reacting gases, surface area of reacting solids, and the use of catalysts. Chemical reactions can only happen if reactant particles collide with enough energy.

The more frequently particles collide, and the greater the proportion of collisions with enough energy, the greater the rate of reaction.

• Concentration: More particles in the same space mean more collisions, therefore more collisions means more effective collisions. Consequently, if we double the concentration, the number of collisions is doubled.

• Temperature: Particles turn heat energy into kinetic energy. When they get hotter they move faster they collide more often. This means more effective collisions.

• Catalysts: These reduce the activation energy needed for a reaction by offering an alternative route for the reaction to take. Less activation energy means more effective collisions.

• Surface Area: Using smaller particles increases rate and increase in surface area allows more collisions. More collisions mean more effective collisions mean a faster rate.

Science Explained - Rhubarb investigation • Rhubarb contains oxalic acid (ethanedioic acid) which has the formula C2H2O4.

• Oxalic acid reacts with the purple potassium manganate(VII) in acidic solutions and is oxidised to carbon

dioxide and water:2MnO4 + 5C2H2O4 + 6H3O + → 2Mn2+ + 10CO2 + 14H2O.

• The potassium manganite (VII) decolourises which provides a convenient and easy-to-measure end-point to

the reaction.

• Aqueous solutions of Mn2+ are actually pale pink, but at these concentrations will appear almost colourless.

• Students should be able to observe that as the surface area of the rhubarb increases (i.e. as they chop it up),

so does the rate of the reaction.


1. Chemical reactions are caused only by mixing of substances.

From NASA (bit.ly/from-NASA)

2. Understanding the factors that influence the rate of a chemical reaction is a fairly complex, but completely

logical affair. Pupils readily accept the idea that molecules must collide if a reaction is to occur. However,

many children have the misconception that every collision leads to the formation of a new product, when the

truth of the matter is that many collisions do not go anywhere. A huge percentage of molecules within a

sample may collide without ever turning into products.





http://bit.ly/from-NASA


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3. Some very sensitive fire detection systems may pick up the smoke and thermal plumes from these reactions so it is recommended that this investigation takes place with all windows open and/or in a very large room.

4. Be aware of any respiratory problems before conducting the icing sugar explosion. 5. Do not use rhubarb leaves. Rhubarb leaves contain far more oxalic acid than the stalk,

and are HARMFUL.





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.

Learning Outcomes

All children should

Handle chemicals safely. Use bar graphs to record data. Be able to describe examples of a slow and a fast chemical reaction. Develop the skill of handling a range of experimental apparatus in conducting a

chemistry experiment and recording data accurately and precisely. Recognize that different chemical reactions take place at different rates.

Some children could

Use bar and line graphs to record data. Take measurements, using a range of scientific equipment, with increasing accuracy

and precision. Recording data and results of increasing complexity using scientific diagrams and labels,

classification keys, tables, scatter graphs, bar and line graphs. Describe different ways to increase the rate of a chemical reaction.


State clearly that their results are valid because of the various factors they controlled. Take measurements, using a range of scientific equipment, with increasing accuracy

and precision, take repeat readings when appropriate. Explain why increasing the surface area of reactants increases the rate of chemical

reaction. Be able to research and explain the 4 main factors that affect the rate of a chemical

reaction. Write a short report identifying other chemical reactions that they can think of and

stating how these reactions could be made to speed up or slow down. Think about different ways in which the speed of chemical reactions is important in

medicine from painkillers to anaesthetics and antibiotics.


Recap understanding of particles and chemical reactions.

The particle theory helps to explain properties and behaviour of materials by providing a model which enables us to visualise what is happening on a very small scale inside those materials. As a model it is useful because it appears to explain many phenomena but as with all models it does have limitations. A chemical reaction is a process that leads to the change of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, often coming about only after the input of some type of energy, such as heat, light or electricity.


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Warn students not to consume anything in the lab – they may be tempted to taste the rhubarb (although it doesn’t taste very good unsweetened). Do not use rhubarb leaves. Rhubarb leaves contain far more oxalic acid than the stalk, and are HARMFUL.


Very fast, Fast and slow chemical reactions Three simple demonstrations which clearly show differing rates of reaction, culminating in a sweet, sugary explosion which will capture the imagination of all learners. These demonstrations are an excellent way of introducing the concept of rate or speed of chemical reactions and easily allow pupils to see different rates of reaction and gain an understanding of sum of the factors that determine rate.

Demonstration 9.1 – Rusting Nail (very slow)

You will need: a nail, a beaker, water

1. Place a nail in a beaker filled with tap water. 2. Ask the class what they think might happen to the nails – some should suggest that the nail will go rusty. 3. Ask the class if they can see the nail going rusty! Clearly they will not be able to and should understand that this is a slow chemical reaction. 4. Leave the beaker on a windowsill for a few days and refer to it next lesson, by which time it will clearly have gone rusty. 5. Ask the class to suggest any ways they can think of that could potentially ‘speed up’ this reaction and or slow it down or prevent it.

Demonstration 9.2 – Ethanol Fire (fast)

You will need: a heatproof mat, foil plate, methylated spirits, match

1. Place the foil lid on a heatproof mat. 2. Ensure class is at least two metres away in a circle around the desk. 3. Place an emergency fire blanket, or damp teatowel close at hand. 4. Turn the light down low. 5. Pour 5 ml of methylated spirits in the lid and light with a match. Nb. Some very sensitive fire detection systems may pick up the smoke and thermal plumes from these reactions so it is recommended that this investigation takes place with all windows open and/or in a very large room.

Demonstration 9.3 – Icing Sugar Explosion (very fast)

You will need: paint can and lid, plastic tubing, tea light candles, icing sugar, heatproof mat, sterilizing tablets

1. Completely clear a table at the front of the class. 2. Place the icing sugar tin on a heat proof mat on the table. 3. Turn the lights down low in the class room. 4 Ensure that that the students are sitting down at least four metres away. 5. Light the two small candles in the tin and place directly opposite the tube in the base of the tin. 6. Place about 5 – 6 tbsp of icing sugar in the base of the tin in front of the tube hole, and push the lid down fairly tightly on the tin. 7. Take a deep breath, fully extend the rubber piping and, gripping the tube in your hand, give a ‘strong’ puff of air into the tube. 8. There should be a load bang as the tin lid shoots off and an orange flame appears briefly as the icing sugar powder catches fire.


Order the speed of the reactions. Children will clearly see the how the information given on differing speed can be demonstrated, which should lead

to discussion on real life examples and provoke a range of questions as to what has happened and why. Discuss with students in what ways this experiment is not a fair test therefore potentially leading to invalid data. What data could we gather from these investigations? How would we gather that? How do we know chemical reactions took place? Which changing states did you witness?


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Investigation 10.1 – Rhubarb Investigation

Pairs will need: rhubarb, plastic knife, 100ml beaker, white tile, potassium manganite (VII) solution, 100ml measuring cylinder

Using an investigation to get pupils to work cooperatively in pairs at first and then interactively as a class through whole class discussion. The investigation allows time to record data whilst observing changes. Repeating the experiment allows the opportunity to discuss changes, and compare results with each other. In this experiment, rhubarb stems which contain oxalic acid, are used to decolourise potassium permanganate solution. The experiment is used to show how the rate of reaction is affected by surface area or concentration. The investigation can be completed in a one-hour session, and graphs could be plotted of the results. 1. Cut three 5 cm lengths of rhubarb. Leave one piece as it is, cut one piece in half lengthways, and cut the third piece into four evenly-sized pieces/mash. 2. Measure 20 ml of potassium permanganate solution into a beaker. Pour the same quantity of water into another beaker. 3. Place the beakers on a white tile. Put the whole 5 cm long piece of rhubarb into the potassium permanganate solution and start the timer. Stir the solution containing the rhubarb until the purple colour disappears. If you are not sure, briefly remove the rhubarb and compare the colour of the solution to the beaker of water. When they look the same, stop the timer. 4. Rinse out and dry the reaction beaker. 5. Repeat the experiment using the piece of rhubarb cut into two (use both halves). Rinse and dry the beaker. 6. Repeat the experiment again, this time using the piece of rhubarb cut into four/ mashed piece. Further information can be found at: bit.ly/rhubarb-rates Pupils could also try this experiment with rhubarb juice and change the concentration by diluting it, the rate of the reaction decreases with weaker concentrations.


• What did children notice comparing reactions? • What explanations can they think of? Make a class list and discuss possibilities, sharing existing knowledge

and observations. • Does the size of a rhubarb (reactant) have any effect on the speed of a chemical reaction?

• How could you repeat this experiment to make it more precise? • Would it work with other fruit and vegetables? How would we find out? • Were there any patterns with results recorded?


1. Ask the class what they learnt / discovered…providing the wherewithal so that children can say ‘I used to think ......... and now I think.......... because ......’ or


Data can then be collected, compared and graphed as appropriate to age group, either as a class, or

independently. A discussion about the best type of graph in which to present this data could be done and then the

class instructed to try and complete one of their own or work together on a single type.

Suggest other ways data could have been recorded? What other measurements could have been made? How could this experiment be improved to make the data more precise accurate and valid? In what ways might data from this type of experiment be useful in the real world?

http://bit.ly/rhubarb-rates


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Literacy

Writing instructions for other classes/younger children, for each investigation. Creative writing/ newspaper report involving a mysterious explosion in a sugar factory

etc. Wide use of vocabulary used to describe what children have seen, e.g. synonyms and

antonyms, alliteration etc. Complete a class glossary of scientific terms.

Numeracy

Accurately recording data, comparing data and commenting on its accuracy and precision.

Draw a range of tables and graphs from data recorded. Develop measuring skills, e.g., measuring length/weight of rhubarb/timing investigation Introduction to the concept of surface area.

Other subjects Cooking with rhubarb. Research the Imperial Sugar explosion near Savannah in 2008, caused by a dust

explosion.

Useful websites


Animation showing ways to increase reaction rates. In depth look at the effect of surface area. Using a diagram of a divided cube to show increase in surface area. Steve Spangle demonstrating burning fine powder. Particle size and dissolving.

bit.ly/5-ways-to-change-reaction-rates bit.ly/effect-of-surface-area bit.ly/cube-diagram bit.ly/fine-dust-explosion bit.ly/from-NASA

http://bit.ly/5-ways-to-change-reaction-rates

http://bit.ly/effect-of-surface-area

http://bit.ly/cube-diagram

http://bit.ly/fine-dust-explosion

http://bit.ly/from-NASA


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Lessons 11 & 12: Simple Chemical Reactions (4)


Disappearing plastic The expanded polystyrene does not actually dissolve in the propanone; it merely collapses as air escapes when the propanone is absorbed. An interesting example of a gas formed not by a chemical process, but by a physical process. The resulting colloidal gel consists of propanone molecules dispersed in a network formed by a tangle of large polystyrene molecules – a similar structure to ordinary jelly in which water molecules are dispersed in a network of protein molecules. You could use the analogy of spaghetti Bolognese with the long polystyrene molecules being the spaghetti and the propanone being the mince.

Burning Paper Paper is mostly made from a chemical called cellulose that comes from plants and consists of C (carbon) H (hydrogen) and O (oxygen). When it is burnt, the chemical reaction is effectively most like respiration i.e

cellulose + oxygen → carbon dioxide + water (+ energy) The ash that is left is largely composed of unreacted cellulose, kaolin, clay, alum, talc and carbon.

Burning Iron Wool Iron in steel wool reacts with oxygen from the air to form iron oxides. The oxygen from the air has weight and adds to the weight of the iron. The result is material that is heavier than the iron alone. The reaction is:

iron + oxygen iron oxide 4Fe + 3O2 2Fe203


1. Materials do not disappear when they dissolve.

2. Mass is associated with the term ‘massive’ and thus related to the size or volume of an object. The term

mass relates to the amount of matter in an object.

3. Gases do not have mass or weight. Fact: Gases are matter, and thus they have mass and weight.

4. There is a loss in mass when matter burns. Fact: Mass is conserved. Gases produced by combustion have

masses.




2. Wear eye protection and ensure children are at a safe distance for the demonstration. 3. Acetone is flammable so keep away from naked flames. 4. Children must wear eye protection for the investigation. 5. Ensure the batteries do not come in to contact with the iron wool.




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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.

Learning Outcomes

All children should

Decide upon the best way to present their data. Explain whether or not their data is valid. Learn the term mass and use when explaining observations. Understand that chemical reactions can involve an increase and a decrease in mass.

Some children could

Report and present findings from enquiries, including conclusions, causal relationships and explanations of and degree of trust in results, in oral and written forms such as displays and other presentations.

Record data and results of increasing complexity using scientific diagrams and labels, classification keys, tables, scatter graphs, bar and line graphs.

Learn the term ‘combustion’, and that it involves a reaction with oxygen. Understand that chemical reactions can involve an increase and a decrease in mass,

but that the mass is not destroyed – simply changed in form and that some mass may enter a reacting system and others leave.

Calculate and compare mass changes in reactions.


Accurately explain mass changes in chemical reactions in terms of particles. An interesting and useful reaction pupils could do is removing the dark tarnish from

any silver objects they have – visit the site below and ask pupils to write up a short experimental report on what they did and what they observed with extra points for clear demonstration of understanding. Pupils should explain why the tarnished spoon’s mass decreases and the aluminium foil increases in mass. bit.ly/polishing-silver


Ensure children are aware of the difference between weight and mass: Weight is different from mass. Weight is the measure of the force of gravity on an object. The mass of an object will never change, but the weight of an item can change based on its location. For example, you may weigh 100 pounds on Earth, but in outer space you would be weightless. However, you will always have the same mass on Earth as you have in outer space. Weight is a force caused by gravity. The weight of an object is the gravitational force between the object and the Earth. The more mass, the object has the greater its weight will be. Weight is a force, so it's measured in Newton’s.

Children could try converting the weight of some objects into Newton’s. (1N = 9.8 kgs)


Demonstration 11.1 – Disappearing Plastic

You will need: mug, acetone, polystyrene blocks/chips

Engaging children through an investigation where a solid seems to ‘disappear’. When expanded polystyrene is placed in acetone, the polystyrene apparently disappears, and the gas bubbles within the material create a fizzing effect as they are released. A small volume of propanone can absorb an impressive volume of expanded polystyrene, making this an attention-grabbing demonstration.

1. Place about 5 ml of acetone into the bottom of the mug without the class seeing you do so and ‘casually’ place small handfuls of the foam into the mug from a significant volume on your desk during an unrelated discussion with the class.

http://bit.ly/polishing-silver


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2. The expanded polystyrene will quickly ‘dissolve’ in the propanone and a quite staggering quantity will ‘disappear’ into the mug.

Demonstration 11.2 – Combustion of Paper

You will need: foil plate, heatproof mat, balance scales, sheet of paper, match

1. Place the foil plate on the mass balance and ‘Tare’ or ‘Zero’ the display. 2. Lightly crumple up 1 sheet of A4 paper on the tin lid on the balance to check and record the mass. 3. Place the foil plate and paper on a heat proof mat and ask the class whether they think the mass will go up or down when it is burnt – get the class to suggest this change in terms of grams and percentages. 4. Ignite the paper and burn it completely and then reweigh. 5. The mass should have decreased by approximately 90% which pupils should find quite surprising. 6. Ask the class to explain why there was a change in mass and where this mass (mostly molecules of CO2 and water) has gone.


This investigation raises discussions over dissolving and disappearing, and allow you the opportunity to correct common misconceptions about mass and volume changes in chemical reaction.

Did the plastic disappear?

Ask the class about changing mass in chemical reactions and if they think there has been one here.

Ask the class how they would go about proving there has not been a change in mass but simply a change in volume. See if they can suggest any other examples of where this happens such as compressing gas in a football pump etc.


Investigation 12.1 – Combustion of Iron Wool

Pairs will need: ball of iron wool, balance scales, foil plate, heatproof mat, 2 x leads, 9v battery

In small groups learners can enjoy the sizzle of burning iron wool in the investigation, whilst also drawing on their existing knowledge to explain what is happening. Accurate repeated measuring allows for the identification of anomalies and an ideal opportunity for comparing and graphing results. In many ways this is one of the most important chemistry investigations for pupils to carry out as it follows in the footsteps of Lavoisier. It was this experiment (although in the case of Lavoisier who used mercury instead) that allowed him to single handedly revolutionise (excuse the sad pun! ... as he had his head chopped off and it was said ‘it took but a second to cut off his head; a hundred years will not suffice to produce one like it’) the study of chemistry by overturning the so called Phlogiston theory and proving how respiration works. He discovered, as the pupils will see, that there is a direct law governing the ‘ratio’ of reactants in all chemical reactions. Show the pupils how to make their iron wool balls. Explain the procedure to them and emphasise the importance of accurate mass measurement and recording. As part of this, pupils should try really hard not to lose iron oxide before they make their final mass measurements. HEALTH & SAFETY: Pupils must wear eye protection 1. Place the foil plate on the mass balance and ‘Tare’ or ‘Zero’ the display. 2. Put the ball of iron wool on the balance to check and record the mass. 3. Take the ball of iron wool and physically expand it by pulling the bundle of fibres apart to create a large ‘fluffy ball’ (about 10cm across). Do this over the foil plate taking care not to lose any ‘bits’. 4. Remove the foil plate from the balance and place on a table on a heat proof mat. Using two wires connected to either side of a 9V cell with crocodile clips on each end – lightly touch either side of the wire wool ball at the same time for about two seconds. 5. The wire wool should quite spectacularly catch fire. Once it has burnt completely, and allowing a few minutes for the tin lid to cool. Reweigh the wool and record the result. 6. Calculate how much oxygen was used from knowing the mass of the iron wool and iron oxide.


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• How do we know a chemical change took place? • Did the materials change their state? • When chemicals undergo combustion does their mass change? • What happens to the mass of the iron after it is burnt? Why? • What happens to the mass of the paper after it is burnt? Why? • Where did the energy come from?


1. Ask the class what they learnt / discovered…providing the wherewithal so that children can say ‘I used to think ......... and now I think.......... because ......’ or


How could this experiment be improved to make the data more precise accurate and valid? In what ways might data from this type of experiment be useful in the real world? There is an excellent opportunity here to place all of their data in a class table during the experiment to

discuss and demonstrate averages, anomalies, reliability and validity. Initiate a class discussion on what the data really shows and introduce them to the fact that sometimes

experiments do not apparently yield any meaningful numbers. A discussion about the best type of graph in which to present this data could be done and then the class

instructed to try and complete one of their own or work together on a single type.


Literacy Creative writing linked to the beautiful image of the burning iron wool, eg, fireflies. Personification/poetry writing – using the iron wool as a stimulus.

Numeracy

Accurately recording data, comparing data and commenting on its accuracy and precision.

Calculating the change in mass in the iron wool investigation using inverse operations. Rounding/converting measurements using Newtons.

Other subjects

Research Lavoisier and his work on combustion. Regardless of his extraordinary services to the nation and to mankind, Antoine Lavoisier’s connections to the tax agency proved to be fatal to him, for he died in May 1794 during the reign of terror. The Revolutionaries guillotined some 28 tax farmers, including Lavoisier and his father-in-law.

Research the life and times of Joseph Priestley.

Useful websites


Removing tarnish off silver. BBC Bitesize conservation of mass video. Reconstruction of Lavoisier demonstrating conservation of mass. School project report on Joseph Priestley and his discovery of oxygen. BBC video showing the burning iron wool demonstration. Short video linking Priestley and Lavoisier

bit.ly/polishing-silver bit.ly/conservation-of-mass bit.ly/Lavoisier-video bit.ly/Priestley-and-oxygen bit.ly/burning-iron-wool bit.ly/Priestley-Lavoisier-oxygen

http://bit.ly/polishing-silver

http://bit.ly/conservation-of-mass

http://bit.ly/Lavoisier-video

http://bit.ly/Priestley-and-oxygen

http://bit.ly/burning-iron-wool

http://bit.ly/Priestley-Lavoisier-oxygen

Chemistry Lesson Plans – Particle Theory & Chemical Reactions End of SoW Practical Assessment Task

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Assessment Guide

Results, Observations and Analysis from an investigation.

Has the pupil...

Level / Grade / % / Mark /Meeting/ Working towards / Exceeding

expectations.

Direct constant

assistance Some help No help

e.g 0-1 e.g. 2-3 e.g. 4-6

1 They observe and compare objects, living things and events

2 They describe their observations using scientific vocabulary and record them, using simple tables when appropriate.

3 They record their observations in a variety of ways.

4 They provide explanations for observations and for simple patterns in recorded measurements.

5 They record their observations, comparisons and measurements using tables and bar charts.

6 They make a series of observations, comparisons or measurements with precision appropriate to the task

7 They record observations and measurements systematically and, where appropriate, present data as line graphs

8 They make enough measurements, comparisons and observations for the task.

9 They measure a variety of quantities with precision, using instruments with fine-scale divisions.

10 They choose scales for graphs and diagrams that enable them to show data and features effectively.

11 They identify measurements and observations that do not fit the main pattern shown.

12 They draw conclusions that are consistent with the evidence and use scientific knowledge and understanding to explain them.

Total

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