Reversible and Irreversible Changes: a full term of science
Ten ready-to-teach lessons for Year 6 Chemical sciences. Print this pack and the term is prepared: every lesson comes with a step-by-step plan, the questions to ask, a student worksheet, cut-out cards or exit tickets, an assessment kit and every answer.
Start here: five minutes to Monday
- Skim the term at a glance on the next page.
- Print the lesson you need. Each lesson is three A4 sheets: plan, worksheet, cards or tickets.
- Gather the few everyday items under “You need” on the plan. Most come from the kitchen or the supermarket.
- Open the free interactive unit on your board or projector. Every plan tells you which picture to show and when.
- Teach straight from the plan. Timings, talk prompts, misconceptions and answers are all on the one page.
No science background needed
This pack is written for the busy generalist teacher. Each plan explains the science idea in plain words, lists the misconceptions children bring, and gives model answers. The big idea of the term: some changes can go back and some cannot. In a reversible change, such as dissolving, melting, freezing, evaporating or condensing, no new substance is made, and the starting material can be got back. In an irreversible change, such as cooking, burning or rusting, new substances are made and the start cannot easily be got back. Clues to a new substance include a gas, a new colour or smell, and a change that stays.
Two ways to run each lesson
Every lesson works as one 60-minute block, or as two 30-minute sessions. The split point is marked in every plan. Look ahead: the saucers set out in Lesson 3 are read in Lesson 5, and the rust jars set up in Lesson 8 are read in Lesson 9, each about a week later. Lesson 6 needs toast, a hard-boiled egg and cupcakes made beforehand.
Safety and care in one look
Nothing is ever tasted. Check the allergy list before Lessons 1 and 6. An adult pours all hot water and uses the toaster. Wear safety glasses for the fizz test, and gloves for steel wool. Use spirit or digital thermometers, never mercury, and everyone washes their hands after handling food, raw egg or steel wool.
The term at a glance
One lesson a week for a term. Each lesson stands on the ones before it, so run them in order where you can.
| # | Lesson | Children learn and do | You need (in short) |
|---|---|---|---|
| 1 | Can it go back? | Watch ice, chocolate and bread change, and sort twelve everyday changes | An ice cube, chocolate, bread and toast; the change cards |
| 2 | Dissolving: where does it go? | Weigh salt and water before and after dissolving, and find how much salt dissolves | Kitchen scales, cups, salt, teaspoons |
| 3 | Getting it back: filter or evaporate? | Filter sandy and salty water, and set the liquid out to evaporate | Funnels, filter paper, play sand, salt, saucers; the step cards |
| 4 | Melting and freezing | Race ice cubes in five places, and read a thermometer in ice water | Ice cubes, a metal tray, a plastic plate, a tea towel, thermometers |
| 5 | Evaporating and condensing | Find the salt left in the saucers, test where droplets come from, and model the water cycle | The Lesson 3 saucers, coloured ice water, a jar |
| 6 | Cooking: making something new | Compare bread and toast, raw and cooked egg, and batter and cake | Bread, toast, eggs, cake batter and cupcakes |
| 7 | The fizz test | Make a gas from bicarb soda and vinegar, and sort the signs of a new substance | Bicarb soda, vinegar, balloons, thermometers; the sign cards |
| 8 | Rusting: set up a fair test | Set up four jars of steel wool to test what rusting needs | Steel wool, jars, salt, cooking oil, silica gel; the jar labels |
| 9 | Rust results and protecting iron | Read and graph the rust test, and choose how to protect three iron things | The Lesson 8 jars |
| 10 | Show what we know | Make a change detective poster, sit the final check and play the class quiz | A3 paper, the worksheets from the term |
How the sequence builds
Lesson 1 asks the term’s question: can it go back? Lessons 2 and 3 show that dissolved salt is still there and get it back, and Lessons 4 and 5 follow water through its changes of state. Lessons 6 and 7 turn to changes that make new substances, through cooking and the fizz test, and Lessons 8 and 9 test what makes iron rust and how to stop it. Lesson 10 is the change detective poster and the final check.
Curriculum links (Australian Curriculum V9)
The whole term teaches the Science Understanding descriptor AC9S6U04 quoted on the cover. The lessons also work these Science Inquiry and Human Endeavour descriptors:
Assessment in this pack
- Every plan ends with “Answers and look-fors”: what meeting the idea sounds like in a Year 6 voice.
- The assessment sheet near the front has a class observation checklist and a three-level rubric.
- Lesson 10 is the summative pair: a change detective poster with its evidence, plus the “Show what we know” check sheet.
Materials for the whole term
One gathering session covers all ten lessons. Everything on this page comes from the kitchen, the supermarket or the classroom, or can be borrowed; nothing needs a science cupboard. Make the toast, the hard-boiled egg and the cupcakes the day before Lesson 6, and buy soap-free steel wool before Lesson 8.
| Lesson | You need |
|---|---|
| 1 | an ice cube on a plate, two squares of chocolate in a zip-lock bag and a bowl of warm tap water, a slice of bread and a slice of toast made before the lesson; the change cards from this pack |
| 2 | for each group: kitchen scales that read to 1 g, a clear plastic cup, a measuring jug, a teaspoon, a stirring spoon and table salt; magnifiers |
| 3 | for each group: three clear cups, a funnel, three filter papers (or paper towel), three saucers, clean play sand, table salt, spoons and a jug of water; a sunny windowsill; the step cards from this pack |
| 4 | for each group: five ice cubes from the same tray, a metal baking tray, a plastic plate, a cup of tap water, a tea towel, a zip-lock bag, a timer, a thermometer and a cup of crushed ice |
| 5 | the Lesson 3 saucers and magnifiers; for each group a clear cup of ice water with a few drops of food colouring; for the class a large glass jar, hot tap water poured by an adult and a plate of ice cubes |
| 6 | for each group, on a paper plate: bread and toast, a raw egg in a clear cup and a hard-boiled egg cut in half, cake batter and a baked cupcake cut in half; magnifiers; the allergy list checked |
| 7 | for each group: two small plastic bottles, two balloons (latex-free if needed), a funnel, bicarb soda, salt, vinegar, water, a teaspoon, a thermometer, string and a ruler; safety glasses and trays; the sign cards from this pack |
| 8 | for each group: four clear jars, one with a lid, soap-free steel wool in four pieces of about the same size, a silica gel sachet, tap water, salt, cooking oil and gloves; the jar labels from this pack |
| 9 | the Lesson 8 jars with their log strips, magnifiers and gloves; a galvanised nail, a painted bracket and an oiled tool, if you have them |
| 10 | A3 paper and coloured pencils; the worksheets from Lessons 1 to 9; the interactive unit open for the class quiz |
The one-trip list
- From the classroom: clear plastic cups, saucers, spoons, jugs, magnifiers, A3 paper, coloured pencils, string, rulers, timers.
- From the kitchen or the supermarket: table salt, chocolate, bread, eggs, a cake mix or cupcakes, bicarb soda, vinegar, cooking oil, food colouring, zip-lock bags, filter papers, play sand, balloons, soap-free steel wool.
- To borrow: kitchen scales, thermometers (spirit or digital), funnels, a metal baking tray, a large glass jar, safety glasses, gloves.
- Keep for later: silica gel sachets from shoe boxes and parcels, and a few rusty or painted bits of iron.
Safety and care in one look
- Nothing is ever tasted. Check the allergy list before Lessons 1 and 6 (chocolate, wheat, egg and milk).
- An adult pours all hot water and uses the toaster. Use spirit or digital thermometers, never mercury.
- Safety glasses for the fizz test; latex-free balloons if anyone has an allergy. Gloves for steel wool.
- Silica gel sachets stay in their jar. Everyone washes their hands after food, raw egg, sand and steel wool.
Assessment without extra work
The term assesses itself. Every lesson plan ends with answers and look-fors, and Lesson 10 is the summative pair: a change detective poster with its evidence, and the check sheet. This sheet is the place to jot down what you notice along the way.
The three levels
| Idea | Working towards | At standard | Beyond |
|---|---|---|---|
| Reversible changes | says melting can go back | explains with evidence that dissolving and changes of state make no new substance, and how to get the start back | plans how to get a substance back from a mixture, choosing between filtering and evaporating |
| Irreversible changes | says cooking cannot be undone | explains that cooking, burning and rusting make new substances, naming a sign of each | tells a sign of a new substance from a change that only looks similar, such as bubbles in boiling water |
| Investigating | follows the steps of a test | plans a fair test, measures carefully and records results in tables and graphs | explains differences between groups’ results and suggests how to improve the test |
| Using what we know | names a way to stop rust | chooses a way to protect iron and explains how it keeps water and air away | uses the rust results to recommend protection for a real place, such as the coast |
Class observation checklist
| Name | Reversible | Irreversible | Evidence | Fair tests | Explaining |
|---|---|---|---|---|---|
A tick a lesson is plenty; the Lesson 10 check sheet fills the gaps.
Word wall cards
Cut out the cards and build the wall as the words arrive. Lesson 1 starts the wall with reversible change, irreversible change and substance; add dissolve and solution in Lesson 2, and mixture and filter in Lesson 3.
a change that can go back, so the starting material returns
a change that makes a new substance and cannot easily go back
one particular kind of material, such as water, salt or iron
to spread out through a liquid in pieces too small to see
a liquid with something dissolved in it, such as salty water
two or more substances mixed together but not joined, such as sand and water
a material with tiny holes that lets liquid through but catches solid bits
to change from a liquid into a gas
to change from a gas into a liquid
to change from a solid into a liquid
to change from a liquid into a solid
a change between solid, liquid and gas, such as melting
a substance that was not there before the change
the flaky orange-brown substance made when iron combines with oxygen and water
a gas in the air that we breathe, and that iron needs to rust
Dear families
This term in science, Year 6 investigates changes to materials. Some changes can go back, such as melting, freezing and dissolving: these are reversible. Others, such as cooking, burning and rusting, make new substances and cannot easily go back: these are irreversible.
Your child will weigh salt before and after it dissolves and get it back by evaporating the water, race ice cubes, find out where the droplets on a cold cup come from, compare raw and cooked foods, make a gas from bicarb soda and vinegar, and run a week-long test of what makes steel wool rust. By the end of the term, they will make a poster that sorts changes, with evidence.
Try this at home
- Let an ice cube melt in a cup, then put the cup back in the freezer. Is it ice again the next day?
- Dissolve a spoon of salt in a saucer of warm water and leave it on a sunny windowsill. What is left after a few days?
- Look for rust around your home or street. What do the rusty places have in common?
- When you cook together, ask: can this change go back? What clues tell you something new was made?
What to ask your scientist
- Is melting chocolate reversible? Is baking a cake?
- How did you prove the salt was still in the water?
- Where do the droplets on a cold drink come from?
- Which rust jar rusted most, and why?
A small note on care: at school nothing is tasted, an adult handles the hot water and the toaster, and we check for allergies before using any food.
Warm regards,
The Year 6 team
Printed from the free seegongsik Reversible and Irreversible Changes teaching pack · seegongsik.com/au/y6/chemical/AC9S6U04/pack
Can it go back?
Things change all around us: ice melts, toast browns, bikes rust. This term asks one question of every change: can it go back? The class watches three changes, an ice cube melting, chocolate melting in warm water and bread turning into toast, and tests whether each one can be undone. Then groups sort twelve everyday changes. A change that can go back, because nothing new is made, is reversible. A change that makes a new substance and cannot easily go back is irreversible.
We are learning to
- sort changes into reversible and irreversible, using one question: can it go back?
- give a reason for each choice, such as how we could get the starting material back,
- notice the clues that something new has been made.
Success criteria
- I can sort a change and say how it could, or could not, go back.
- I can name a clue that tells me a new substance was made.
You need
- an ice cube on a plate, two squares of chocolate in a zip-lock bag and a bowl of warm tap water, a slice of bread and a slice of toast made before the lesson,
- the change cards (third sheet), cut out, one set per group of three,
- the worksheet (next sheet), one per child.
Lesson flow (about 60 minutes)
| 5 min | Three changes Put the ice cube on its plate and the chocolate bag in the warm water. Pass the bread and the toast around. Ask: “Which of these three could go back to how it started? How?” |
| 15 min | Watch and test Children fill Part A while the ice and chocolate melt. Put the melted chocolate in the fridge and the meltwater in the freezer, and check them at the end of the day. |
| 20 min | Sort the cards Groups sort the twelve cards into “can go back” and “cannot go back”, agreeing on a reason for each, then record Part B. Show the board (see the box). Ask: “For the cards that can go back, what would you do to get the start back?” |
| 15 min | The clues Children answer Part C. Ask: “What do the cards that cannot go back have in common? What clues do you see, smell or feel?” |
| 5 min | The word wall Add reversible and irreversible to the word wall. |
Running two half-sessions instead? Watch the three changes and sort the cards in Session A. Check the freezer and fridge, then answer Part C in Session B.
Watch for these ideas
- “Melting is irreversible because the ice is gone.” The water is still there, and the freezer turns it back into ice.
- “Reversible means it goes back on its own.” Often we have to do something, such as cool it, freeze it or let the water evaporate.
- “Cooking just makes food hot.” The colour, smell and texture change for good, which tells us new substances were made.
Make it easier, make it bigger
- Easier: sort six cards first, three of each kind, then add the rest.
- Bigger: a burning candle has a reversible change and an irreversible change happening at once. Find both.
Answers and look-fors
- Can go back (reversible): C, D, G, H, K. Cannot go back (irreversible): A, B, E, F, I, J, L.
- A: the bread turns brown and crisp and smells different: new substances that cannot turn back into soft bread.
- B: the runny white sets solid and white, and no cooling makes it runny again.
- C: the water can be frozen back into ice.
- D: the sugar is still there; if the water evaporates, it is left behind.
- E: the iron has combined with oxygen and water to make rust, a new substance.
- F: the wood becomes ash, smoke and gases, which cannot be put back together as wood.
- G: the ice melts back into water.
- H: it sets solid again when it cools.
- I: the runny batter becomes a spongy solid with gas holes, and it cannot become batter again.
- J: the cement has combined with the water to make new, hard substances.
- K: the water has evaporated into the air, and it can condense and fall as rain again.
- L: the match head burns to new substances: smoke, gases and a black tip.
- Part C: 1. nothing new is made, so the starting material can come back. 2. clues include a new colour or smell, a change in texture that stays, gas or smoke given off, and no way back. Bigger: the wax melts near the flame and sets again (reversible), and the wax burns into gases and smoke (irreversible).
Can it go back?
A. Three changes we watched
| What we watched | What changed? | Can it go back? How? |
|---|---|---|
| an ice cube on a plate | ||
| chocolate in a zip-lock bag in warm water | ||
| a slice of bread and a slice of toast |
B. Our sort
C. The clues
Change cards
Cut out the cards. Sort them into two piles, can go back and cannot go back, and agree on a reason for each one.
Toasting a slice of bread
Frying an egg
An ice block melting on a hot day
Sugar dissolving in a cup of tea
A bike chain going rusty
Wood burning in a campfire
Water freezing into ice cubes
Chocolate melting in a hot car
Baking a cake
Concrete setting hard on a new footpath
A puddle drying up in the sun
Striking a match
Teacher note: check for food allergies before the chocolate and bread come out. In science we look, smell and touch, but we never taste.
Dissolving: where does it go?
Stir salt into water and it seems to vanish. Has it gone, or is it still there? Groups weigh a cup of water and two spoons of salt, dissolve the salt, and weigh the cup again. The mass stays the same: the salt is still there, spread out in pieces far too small to see. No new substance is made, so dissolving is a reversible change, and in Lessons 3 and 5 the class gets the salt back. Groups also find out how much salt a cup of water can dissolve.
We are learning to
- use measurements as evidence that a dissolved substance is still there,
- measure mass carefully with kitchen scales,
- explain why dissolving is a reversible change.
Success criteria
- I can use the masses before and after to show the salt is still in the water.
- I can explain why dissolving is reversible.
You need
- for each group: kitchen scales that read to 1 g, a clear plastic cup, a measuring jug, a teaspoon, a spoon for stirring and table salt,
- a magnifier, and a small dish of salt to look at,
- the worksheet (next sheet), one per child, and the exit tickets (third sheet).
Lesson flow (about 60 minutes)
| 5 min | Where did it go? Stir a spoon of salt into a clear cup of water in front of the class. Ask: “The salt has vanished. Has it gone? How could we find out without tasting?” |
| 20 min | Weigh it Groups weigh the cup with 100 mL of water and the salt separately, add them, then stir until the salt dissolves and weigh the cup again. They fill Part A. Ask: “Is the scale reading the same? What does that tell you?” |
| 15 min | How much will dissolve? Groups add one level teaspoon at a time to 100 mL of fresh water, stirring well, until some salt stays at the bottom. They record the count in Part B. |
| 15 min | Explain Children answer Part C. Show the board (see the box). |
| 5 min | Exit tickets Children answer one exit ticket each. Keep one cup of salty water for Lesson 3. |
Running two half-sessions instead? Weigh in Session A. Count the spoons and explain in Session B.
Watch for these ideas
- “The salt has disappeared.” It is spread out in pieces too small to see; the mass shows it is still there.
- “Dissolving is the same as melting.” Melting needs heat and happens to one substance; dissolving mixes one substance into another.
- “Water can dissolve as much salt as you like.” There is a limit; after that the salt stays at the bottom.
Make it easier, make it bigger
- Easier: weigh before and after with one bigger spoon of salt, and skip the counting.
- Bigger: does warm water dissolve more salt, or sugar? Plan a fair test to find out.
Answers and look-fors
- Part A: the mass after stirring is the same as the total before (within 1 g, as the scales read to 1 g).
- Part B: about 6 level teaspoons in 100 mL at room temperature (about 36 g); counts vary a little with the spoon.
- Part C: 1. the salt is still there, because the mass did not change. 2. it breaks into pieces far too small to see and spreads through the water. 3. no new substance is made, and the salt can be got back by evaporating the water.
Where did the salt go?
A. Weigh it
| What we weighed | Mass (g) |
|---|---|
| the cup with 100 mL of water | |
| the salt (2 level teaspoons) | |
| total before (add them) | |
| the cup of salty water, after stirring |
B. How much will dissolve?
C. Explain it
Exit tickets
Cut out the tickets. Each child answers one before leaving.
1. Salt dissolved in water. Give one piece of evidence that it is still there.
2. Draw what you think the salt looks like in the water, if you could see tiny pieces.
1. Salt dissolved in water. Give one piece of evidence that it is still there.
2. Draw what you think the salt looks like in the water, if you could see tiny pieces.
1. Salt dissolved in water. Give one piece of evidence that it is still there.
2. Draw what you think the salt looks like in the water, if you could see tiny pieces.
1. Salt dissolved in water. Give one piece of evidence that it is still there.
2. Draw what you think the salt looks like in the water, if you could see tiny pieces.
Teacher note: in science we never taste, even salt water. Pour the salty water down the sink at the end, except one cup kept for Lesson 3.
Getting it back: filter or evaporate?
If dissolving is reversible, we should be able to get the salt back. Groups try a filter first. They pour three mixtures, sandy water, salty water and sandy, salty water, through filter paper. The filter catches the sand, but the dissolved salt goes straight through with the water. Then they leave each saucer of liquid on a sunny windowsill, so the water can evaporate and leave the salt behind. The class reads the saucers in Lesson 5.
We are learning to
- separate mixtures by filtering and by evaporating,
- explain why a filter catches sand but not dissolved salt,
- plan the steps for getting a dissolved substance back.
Success criteria
- I can say which method gets sand back and which gets dissolved salt back.
- I can put the steps for getting the salt back in order and explain each one.
You need
- for each group: three clear cups, a funnel, three filter papers (or paper towel), three saucers, clean play sand, table salt, spoons and a jug of water,
- a sunny windowsill where the saucers can sit for a week, and a marker to label them,
- the step cards (third sheet), one set per group, and the worksheet (next sheet), one per child.
Lesson flow (about 60 minutes)
| 5 min | How do we get it back? Hold up a cup of salty water from Lesson 2. Ask: “The salt is still in here. Could we pour it through a filter to catch it?” |
| 25 min | Filter three mixtures Groups make the three mixtures, stir them well, predict, then filter each one into its own saucer. They fill Part A. Ask: “The salty water came through looking clear. Is the salt still in it?” |
| 10 min | Set them to evaporate Groups label their saucers and set them on the sunny windowsill, to read in Lesson 5. |
| 15 min | Why it went through Children answer Part B and put the step cards in order for Part C. Show the board (see the box). |
| 5 min | Tidy up Sand goes in the bin, not the sink. Rinse the funnels. |
Running two half-sessions instead? Filter the mixtures and set the saucers in Session A. Answer Parts B and C in Session B.
Watch for these ideas
- “The filter caught the salt, so the water is clean.” Dissolved salt passes through filter paper; the water only looks clean.
- “Evaporating gets rid of the salt as well.” Only the water evaporates; the salt is left in the saucer.
- “Filtering and evaporating do the same job.” Filtering separates solid bits that have not dissolved; evaporating gets back what has.
Make it easier, make it bigger
- Easier: filter the sandy water and the salty water only.
- Bigger: how could you get the water back as well as the salt? (Catch the water vapour on something cold so it condenses.)
Answers and look-fors
- Part A: sandy water: the paper catches the sand, and clear water comes through; salty water: the paper catches nothing, and the water with the salt still dissolved in it comes through; sandy, salty water: the paper catches the sand, and the water with the salt still dissolved in it comes through.
- Part B: 1. the pieces of dissolved salt are far smaller than the holes in the filter paper, so they pass through with the water; grains of sand are too big. 2. evaporate some of it: salt crystals are left behind (Lesson 5).
- Part C: B, D, F, A, E, C. The sun evaporates the water, and the salt crystals are left behind.
Filter or evaporate?
A. Filter three mixtures
| Mixture | I predict the filter will catch | On the filter paper | What came through |
|---|---|---|---|
| sandy water | |||
| salty water | |||
| sandy, salty water |
B. Why did it go through?
C. Getting the salt back
Step cards
Cut out the cards and put them in order, from salty, sandy water to salt crystals you can see. Each step must come after the one before it.
Leave the saucer of liquid on a sunny windowsill until all the water has gone.
Add two spoons of sand and one spoon of salt to a cup of water.
Look at the crystals with a magnifier. Do they look like the salt you started with?
Stir until all of the salt has dissolved. The sand will not dissolve.
Scrape the white crystals off the saucer.
Pour it through a filter paper in a funnel, with a saucer underneath. The sand stays on the paper.
Teacher note: use clean play sand from a bag. Sand goes in the bin, not down the sink, and nothing is tasted.
Melting and freezing
Melting and freezing are changes of state: the water is the same substance as a solid or as a liquid. Groups run a fair test of where an ice cube melts fastest, with same-sized cubes in five places, checked every 5 minutes for 30 minutes. Meanwhile they read a thermometer in a cup of ice water and find that it stays close to 0 °C for as long as there is ice. The meltwater goes back into the freezer, and the next day it is ice again.
We are learning to
- plan and run a fair test, keeping everything the same except the place,
- measure time and temperature and show the results in a column graph,
- explain why melting and freezing are reversible changes of state.
Success criteria
- I can say what we changed, what we kept the same and what we measured.
- I can explain, with evidence, why melting can go back.
You need
- for each group: five ice cubes from the same tray, a metal baking tray, a plastic plate, a cup of tap water, a tea towel, a zip-lock bag and a timer,
- a thermometer (spirit or digital) and a cup of crushed ice with a little water for each group,
- the worksheet (next sheet), one per child, and the exit tickets (third sheet).
Lesson flow (about 60 minutes)
| 5 min | Where will it melt fastest? Show the five places. Ask: “Which ice cube will melt first, and which last? Why do you think so?” |
| 10 min | Set up Groups write their prediction in Part A, then put one cube in each place at the same moment and start the timer. The hand-holders take turns, so nobody holds the bag for long. |
| 30 min | Check and read Every 5 minutes, groups check the cubes and record any that have fully melted. In between, they read the thermometer in the ice water every 2 minutes for Part C. Ask: “The ice is melting, so why is the thermometer not going up?” |
| 15 min | Graph and explain Children draw the graph in Part B and answer Part D. Pour the meltwater into a labelled cup for the freezer. Show the board (see the box). |
Running two half-sessions instead? Set the cubes going at the very start of Session A and check them, with the thermometer readings, until the session ends. Graph and explain in Session B.
Watch for these ideas
- “The tea towel keeps the ice warm, so it melts faster.” The towel slows the heat getting in from the room, so that cube usually lasts longest.
- “Metal is cold, so the ice on the tray melts slowest.” Metal feels cold because it carries heat well, and it carries heat from the room into the ice, so that cube usually melts faster than the one on the plastic plate.
- “Melted ice is a new substance called water.” Ice and water are the same substance in two states.
Make it easier, make it bigger
- Easier: compare three places only: the metal tray, the plastic plate and the tea towel.
- Bigger: design a box that keeps an ice cube frozen for as long as possible, and test it against the tea towel.
Answers and look-fors
- Parts A and B: results vary with the room. Usually the cube in the cup of water or in the hand melts first, then the one on the metal tray, then the one on the plastic plate, and the tea towel cube last, often still there at 30 minutes.
- Part C: the readings stay close to 0 °C (within a degree or two) for as long as there is ice in the cup.
- Part D: 1. the towel is an insulator that slows the heat from the room reaching the ice. 2. it will be ice again: melting and freezing are changes of state of the same substance, water, so they can go back and forth.
The ice cube race
A. Our fair test
| Place | Minutes to melt (or still ice at 30) |
|---|---|
| on a metal baking tray | |
| on a plastic plate | |
| in a cup of tap water | |
| wrapped in a tea towel | |
| in a zip-lock bag, held in a hand |
B. Our graph
C. A thermometer in ice water
| Minutes | 0 | 2 | 4 | 6 | 8 | 10 |
|---|---|---|---|---|---|---|
| °C |
D. Explain it
Exit tickets
Cut out the tickets. Each child answers one before leaving.
1. Name two things we kept the same to make the ice cube race fair.
2. Ice melts into water. Is water a new substance? Explain.
1. Name two things we kept the same to make the ice cube race fair.
2. Ice melts into water. Is water a new substance? Explain.
1. Name two things we kept the same to make the ice cube race fair.
2. Ice melts into water. Is water a new substance? Explain.
1. Name two things we kept the same to make the ice cube race fair.
2. Ice melts into water. Is water a new substance? Explain.
Teacher note: use spirit or digital thermometers, never mercury. Holding ice in a bag gets painful quickly, so swap hands often and stop if it hurts.
Evaporating and condensing
A week ago the class left saucers of filtered water on a sunny windowsill. Now the water has evaporated, and two saucers hold white crystals: the dissolved salt, back again. Evaporating turns liquid water into water vapour, a gas in the air; condensing turns the vapour back into liquid. Children show this with a cold cup of coloured water, whose clear droplets on the outside can only have come from the air, and with a jar model of the water cycle.
We are learning to
- use evaporation to get a dissolved substance back,
- describe evaporating and condensing as changes of state that go both ways,
- use evidence to decide where condensed water comes from.
Success criteria
- I can explain what is left in the saucers and where the water went.
- I can use the coloured water test to show that droplets come from the air.
You need
- the saucers from Lesson 3, magnifiers, and for each group a clear plastic cup with ice, water and a few drops of food colouring,
- for the class jar model: a large glass jar, hot tap water (poured by an adult) and a plate of ice cubes to sit on top,
- the worksheet (next sheet), one per child, and the exit tickets (third sheet).
Lesson flow (about 60 minutes)
| 15 min | Read the saucers Groups look at their saucers with a magnifier and fill Part A. Ask: “Where did the water go? Why did the salt stay behind?” |
| 15 min | The cold cup test Groups set their coloured ice water on the desk and wait. Droplets form on the outside. They wipe some off with a white tissue and fill Part B. Ask: “The water inside is coloured. What colour are the droplets? So where did they come from?” |
| 15 min | A water cycle in a jar An adult pours hot water into the jar; the plate of ice goes on top. The class watches mist and drips form under the plate. Show the board (see the box). |
| 10 min | Draw the model Children draw and label the jar model in Part C. |
| 5 min | Exit tickets Children answer one exit ticket each. |
Running two half-sessions instead? Read the saucers and run the cold cup test in Session A. Start Session B with the jar model.
Watch for these ideas
- “The water soaked through the cup.” The droplets are clear while the water inside is coloured, so they came from the air.
- “Evaporated water is gone for good.” It is water vapour in the air, and it condenses back into liquid on cold things.
- “The salt evaporated too.” Only the water evaporates; the salt is left in the saucer.
Make it easier, make it bigger
- Easier: read the salty water saucer and do the cold cup test; watch the jar model as a class.
- Bigger: why does a bathroom mirror fog up during a hot shower? Use the words evaporate and condense.
Answers and look-fors
- Part A: the sandy water saucer is nearly empty (perhaps a little dust); the two salty saucers have white salt crystals. The water evaporated into the air; the salt did not.
- Part B: the droplets are clear, not coloured, so they did not come through the cup. Water vapour in the air condensed on the cold cup.
- Part C: the hot water evaporates, the water vapour rises, condenses into droplets under the cold plate, and drips back down like rain. Evaporating and condensing are changes of state of the same water, so they can go both ways.
Where does the water go?
A. Our saucers from Lesson 3
| Saucer | What is left in it now? |
|---|---|
| sandy water (filtered) | |
| salty water (filtered) | |
| sandy, salty water (filtered) |
B. The cold cup test
C. A water cycle in a jar
Exit tickets
Cut out the tickets. Each child answers one before leaving.
1. What is the difference between evaporating and condensing?
2. How did we get the dissolved salt back?
1. What is the difference between evaporating and condensing?
2. How did we get the dissolved salt back?
1. What is the difference between evaporating and condensing?
2. How did we get the dissolved salt back?
1. What is the difference between evaporating and condensing?
2. How did we get the dissolved salt back?
Teacher note: an adult pours and carries the hot water, and the jar stays on a steady bench. Food colouring stains, so use only a few drops.
Cooking: making something new
Melting chocolate and baking a cake both use heat, but only one of them can go back. Groups compare three foods before and after cooking: bread and toast, a raw egg and a hard-boiled egg, and cake batter and a baked cupcake. They list what each looked, felt and smelled like before and after, and find the clues that cooking has made new substances: new colours, smells and textures that stay, holes left by a gas, and no way back. Cooking is an irreversible change.
We are learning to
- observe and record the properties of foods before and after cooking,
- use clues to decide that a new substance has been made,
- explain the difference between melting and cooking.
Success criteria
- I can describe a food before and after cooking using at least two senses.
- I can name two clues that a new substance has been made.
You need
- for each group, on a paper plate: a slice of bread and a slice of toast, a raw egg in a clear cup and a hard-boiled egg cut in half, a spoon of cake batter in a cup and a baked cupcake cut in half,
- magnifiers, and the school’s allergy list (egg, wheat and milk) checked before the lesson,
- the worksheet (next sheet), one per child, and the exit tickets (third sheet).
Lesson flow (about 60 minutes)
| 5 min | Two kinds of heating Recall the chocolate from Lesson 1. Ask: “The chocolate melted and set again. Will a cake turn back into batter if it cools?” |
| 25 min | Before and after Groups look at, feel and smell each pair (no tasting), using magnifiers, and fill Part A. Ask: “Look at the cupcake through the magnifier. What made all those holes?” |
| 15 min | The clues Children tick the clues in Part B for each food. Show the board (see the box). |
| 10 min | Melting against baking Children answer Part C. |
| 5 min | Exit tickets Children answer one exit ticket each, then wash their hands. |
Running two half-sessions instead? Compare the foods in Session A. Start Session B with the clues.
Watch for these ideas
- “The toast is just dried-out bread.” Drying alone would not make it brown or smell toasty; the heat has made new substances.
- “The egg white turned white because it got hot, and it will go clear when it cools.” A cold hard-boiled egg stays white: the change stays.
- “Any change with heat is irreversible.” Melting uses heat and can go back; the test is whether a new substance is made.
Make it easier, make it bigger
- Easier: compare bread and toast, and the two eggs, only.
- Bigger: in a cake, baking powder makes a gas. Find out which gas, and why it makes the cake rise.
Answers and look-fors
- Part A: a slice of bread (soft, pale, bendy, smells of bread) becomes toast (crisp, brown, snaps, smells toasty); a raw egg (the white clear and runny, the yolk runny) becomes a hard-boiled egg (the white solid and white, the yolk firm and crumbly); cake batter (a thick, pale liquid that pours) becomes a baked cupcake (a light, golden, spongy solid full of holes).
- Part B: all three show a new texture that stays and cannot go back; toast and cake show a new colour and smell; the cake shows holes from a gas.
- Part C: melting changes the chocolate from solid to liquid, but it is still chocolate, so it sets again when cool; baking makes new substances, so the cake cannot become batter again.
- Bigger: carbon dioxide; its bubbles get trapped in the batter as it sets.
Before and after cooking
A. What changed?
| Food | Before: look, feel, smell | After: look, feel, smell |
|---|---|---|
| a slice of bread → toast | ||
| a raw egg → a hard-boiled egg | ||
| cake batter → a baked cupcake |
B. The clues to a new substance
| Clue (tick each one you saw) | toast | a hard-boiled egg | a baked cupcake |
|---|---|---|---|
| a new colour that stays | |||
| a new smell | |||
| a new texture that stays | |||
| bubbles or holes from a gas | |||
| it cannot go back |
C. Melting against baking
Exit tickets
Cut out the tickets. Each child answers one before leaving.
1. Name two clues that cooking made a new substance in the toast.
2. Is boiling an egg reversible or irreversible? How do you know?
1. Name two clues that cooking made a new substance in the toast.
2. Is boiling an egg reversible or irreversible? How do you know?
1. Name two clues that cooking made a new substance in the toast.
2. Is boiling an egg reversible or irreversible? How do you know?
1. Name two clues that cooking made a new substance in the toast.
2. Is boiling an egg reversible or irreversible? How do you know?
Teacher note: check the allergy list before the lesson, keep the food on plates, and make sure nothing is eaten. Everyone washes their hands afterwards, especially after the raw egg.
The fizz test
How can we tell when a new substance has been made? Groups put two teaspoons of bicarb soda into a balloon, stretch it over a bottle of vinegar and tip the powder in. It fizzes, the balloon fills with a new gas, carbon dioxide, and the liquid gets a little colder. For comparison they tip salt into water the same way: it dissolves, but nothing fizzes and the balloon stays flat. Then groups sort nine observations into signs of a new substance and changes that make nothing new.
We are learning to
- observe and measure the signs that a new substance has formed,
- compare a change that makes a new substance with one that does not,
- tell a sign of a new substance from a change of state or dissolving.
Success criteria
- I can name three signs of a new substance from the fizz test.
- I can explain why bubbles in boiling water are not a new substance.
You need
- for each group: two small plastic bottles, two balloons (latex-free if anyone has an allergy), a funnel, bicarb soda, table salt, vinegar, water, a teaspoon, a thermometer, string and a ruler,
- safety glasses for everyone, trays to catch spills, and paper towel,
- the sign cards (third sheet), one set per group, and the worksheet (next sheet), one per child.
Lesson flow (about 60 minutes)
| 5 min | How can we tell? Recall the toast and the cupcake from Lesson 6. Ask: “What clues told us something new had been made? Could a gas be one?” |
| 25 min | The fizz test Groups pour 50 mL of vinegar into one bottle and 50 mL of water into the other, and take each temperature. They funnel two teaspoons of bicarb soda into one balloon and two of salt into the other, stretch each over its bottle, and tip the powder in. After one minute they measure around each balloon with string and take each temperature again for Part A. Ask: “What is inside the balloon now? Was it there before?” |
| 20 min | Sort the signs Groups sort the nine cards into “a new substance” and “nothing new”, then fill Part B. Show the board (see the box). Ask: “Card B has bubbles too. Why does it go in the other pile?” |
| 10 min | Explain Children answer Part C. |
Running two half-sessions instead? Run the fizz test in Session A. Start Session B with the sign cards.
Watch for these ideas
- “Any bubbles mean a new substance.” Bubbles in boiling water are water as a gas; the test is whether the gas is a different substance.
- “The bicarb soda just dissolved.” Dissolving makes no gas and no balloon; the salt showed what dissolving looks like.
- “The gas is air.” The balloon held no air to begin with; the gas came from the bicarb soda and vinegar, and it is carbon dioxide.
Make it easier, make it bigger
- Easier: run the bicarb soda test as a class, with groups measuring the balloon.
- Bigger: does more bicarb soda make a bigger balloon? Plan a fair test with one, two and three teaspoons.
Answers and look-fors
- Part A: bicarb soda and vinegar fizz hard, the balloon fills (sizes vary), the temperature drops a few degrees, and the start cannot be got back. Salt and water do not fizz, the balloon stays flat, the temperature hardly changes, and the salt can be got back by evaporating.
- Part B: a new substance A, D, E, H, I; nothing new B, C, F, G.
- A: a new gas, carbon dioxide, forms; the bicarb soda and vinegar cannot be got back.
- B: the bubbles are water as a gas (steam); it is a change of state.
- C: it is still water, now a liquid; it can freeze again.
- D: the colour and smell come from new substances made by the heat.
- E: rust is a new substance made from iron, oxygen and water.
- F: it dissolves; it is still there and comes back when the water evaporates.
- G: water vapour from the air condenses on the cold metal.
- H: a new solid forms that will not mix back into milk.
- I: gas bubbles form and the batter sets into a new spongy solid.
- Part C: carbon dioxide gas. It is new because it was not there before, it fills the balloon, and the bicarb soda and vinegar cannot be got back.
Signs of a new substance
A. The fizz test
| What we checked | Bicarb soda + vinegar | Salt + water |
|---|---|---|
| Bubbles? | ||
| Distance around the balloon after 1 minute (cm) | ||
| Temperature before (°C) | ||
| Temperature after (°C) | ||
| Can we get the start back? |
B. Sort the signs
C. Explain it
Sign cards
Cut out the cards. Sort them into two piles: a new substance was made, and nothing new was made.
Gas bubbles pour out when bicarb soda meets vinegar.
Bubbles rise in a pot of boiling water.
Ice cubes melt into a puddle.
Bread turns brown and smells toasty.
A nail grows flaky orange-brown patches.
Sugar disappears when it is stirred into water.
Droplets form on the outside of a cold can.
Milk mixed with vinegar forms white lumps.
Cake batter rises and sets in the oven.
Teacher note: safety glasses on for the fizz test, as vinegar stings the eyes. Work over trays, and wipe up spills straight away.
Rusting: set up a fair test
Rust forms when iron combines with oxygen from the air and with water. It makes a new substance, so rusting is an irreversible change, but it is slow: a nail can take weeks. Steel wool is mostly iron in thin strands, so it rusts in a day or two. Groups set up four jars of steel wool, one dry, one in tap water, one in salty water and one rubbed with cooking oil and put in tap water, predict which will rust most, and record how the steel wool looks now. They check the jars each day, and read them in Lesson 9.
We are learning to
- plan a fair test, deciding what to change, what to keep the same and what to observe,
- make a prediction with a reason,
- describe rusting as a slow, irreversible change that makes a new substance.
Success criteria
- I can say what we are changing, what we are keeping the same and how we will judge the rust.
- I can predict which jar will rust most and give a reason.
You need
- for each group: four clear jars, one with a lid, soap-free steel wool pulled into four pieces of about the same size, a silica gel sachet, tap water, salt, cooking oil and gloves,
- a shelf where the jars can sit for a week, out of the sun,
- the jar labels (third sheet), one set per group, and the worksheet (next sheet), one per child.
Lesson flow (about 60 minutes)
| 10 min | What makes rust? Pass around a rusty nail and a shiny one. Ask: “Where have you seen rust? What do those places have in common?” |
| 15 min | Plan it Groups fill Part A: what changes from jar to jar, what stays the same, and how they will judge the rust with the rating on the labels. Show the board (see the box). |
| 20 min | Set it up Wearing gloves, groups set up the four jars to match their labels, then predict in Part B. Ask: “Why must the four pieces of steel wool be about the same size?” |
| 10 min | Day 0 Groups describe each piece now, in Part C, and stick the labels on the jars. |
| 5 min | Every day this week A different child each day checks the jars and writes a rating on each label’s log strip. |
Running two half-sessions instead? Plan the test in Session A. Set it up and record day 0 in Session B.
Watch for these ideas
- “Rust is dirt on the outside of the iron.” Rust is a new substance made from the iron itself; as it forms, the iron is used up.
- “Iron rusts because it is old.” It rusts because of water and oxygen; iron kept dry can stay shiny for years.
- “Rust can be scrubbed back into iron.” Scrubbing takes the rust off, but the iron that became rust is gone.
Make it easier, make it bigger
- Easier: set up two jars only, dry and tap water.
- Bigger: add a fifth jar: steel wool in water that an adult has boiled to drive out the air, cooled, and covered with a layer of oil. Predict what happens without oxygen.
Answers and look-fors
- Part A: we change the conditions around the steel wool; we keep the same the size and kind of steel wool, the jars, the amount of liquid, the place and the time; we observe the rust each day and rate it from 0 to 3.
- Part B: predictions vary. Most rust is usually in the salt water jar; the least in the dry jar.
- Part C: on day 0 every piece is grey and shiny, with no orange-brown.
Our rust test
A. Plan it
B. Predict
C. Day 0
| Jar | What the steel wool looks like now |
|---|---|
| Dry | |
| Tap water | |
| Salt water | |
| Oiled |
Rust rating: 0 no rust, 1 a few spots, 2 patches, 3 rusty all over.
Jar labels and log strips
Cut out the labels and tape one to each jar. Each day, write the rust rating (0 to 3) in the next box.
steel wool in a dry jar with a silica gel sachet, lid on
steel wool half in tap water, lid off
steel wool half in salty water, lid off
steel wool rubbed with cooking oil, half in tap water, lid off
Teacher note: wear gloves for steel wool, as its strands splinter. Silica gel sachets say “do not eat”: keep them in the jar. Everyone washes their hands after the set-up.
Rust results and protecting iron
A week after setting up the rust test, groups read their jars. The steel wool in salty water is usually the rustiest, then the one in tap water; the oiled one has only a little rust, and the dry one has none. So rust needs water (and the oxygen in air), salt speeds it up, and a coat that keeps water and air off slows it down. Groups graph the results, then use what they found to protect three iron things, from a garden spade to a bike rack at a school near the beach.
We are learning to
- present results in a table and a column graph, and draw a conclusion from them,
- compare our results with our predictions and with other groups’,
- use what we know about rusting to make decisions about protecting iron.
Success criteria
- I can say what our results show about what rusting needs and what slows it.
- I can choose a way to protect an iron thing and explain how it works.
You need
- each group’s four jars from Lesson 8, with their log strips, and magnifiers,
- a few rusty and protected things to look at (a galvanised nail, a painted bracket, an oiled tool), if you have them,
- the worksheet (next sheet), one per child, and the exit tickets (third sheet).
Lesson flow (about 60 minutes)
| 15 min | Read the jars Groups look closely at each jar, copy the week’s ratings from the log strips and agree on a final rating for Part A. Ask: “Do all the groups agree? If not, why might their jars be different?” |
| 10 min | Graph it Children draw the column graph of the final ratings in Part B. |
| 15 min | What did we find? Children answer Part C. Show the board (see the box). Ask: “What does the dry jar tell us that the others cannot?” |
| 15 min | Protect it Pass around the protected things. Children fill Part D. Ask: “How does each coat keep the water and air off the iron?” |
| 5 min | Exit tickets Children answer one exit ticket each. |
Running two half-sessions instead? Read the jars and graph them in Session A. Draw conclusions and protect the iron things in Session B.
Watch for these ideas
- “Salt makes rust.” Salt on its own does not; it speeds up the rusting that water and oxygen cause.
- “Paint stops rust forever.” Only while it covers the iron: a scratch lets water and air in, and rust can spread under the paint.
- “Stainless steel cannot rust.” It rusts far more slowly, but it can still stain, especially in salty air.
Make it easier, make it bigger
- Easier: compare the dry jar with the tap water jar, and protect the spade only.
- Bigger: find out what galvanised means, and why sheds, fence posts and boat trailers are often galvanised.
Answers and look-fors
- Parts A and B: results vary; usually salt water 3, tap water 2, oiled 1, dry 0.
- Part C: 1. usually the salt water jar most and the dry jar least. 2. with no water there was no rust, so rusting needs water. 3. the oil coated the strands and kept most of the water and air off.
- Part D: a steel bike rack at a school near the beach: galvanise it (coat it with zinc) or paint it, and hose off the salt now and then; a steel garden spade: clean and dry it after use, wipe it with oil and keep it in the shed; the steel plate of a barbecue: wipe on a thin layer of cooking oil after cooking and keep the cover on. Each works by keeping water, salt or air away from the iron.
- Bigger: galvanised steel has a coat of zinc, which keeps water and air off the iron and protects it even where the coat is scratched.
What made the most rust?
A. Our ratings (0 to 3)
| Jar | Day 1 | Day 2 | Day 3 | Day 4 | Day 5 | Final |
|---|---|---|---|---|---|---|
| Dry | ||||||
| Tap water | ||||||
| Salt water | ||||||
| Oiled |
B. Our graph
C. What did we find?
D. Protect it
| Iron thing | How I would protect it, and how that works |
|---|---|
| a steel bike rack at a school near the beach | |
| a steel garden spade | |
| the steel plate of a barbecue |
Exit tickets
Cut out the tickets. Each child answers one before leaving.
1. Name the two things iron needs to rust.
2. Why does a bike rust faster at the beach? How could you slow it down?
1. Name the two things iron needs to rust.
2. Why does a bike rust faster at the beach? How could you slow it down?
1. Name the two things iron needs to rust.
2. Why does a bike rust faster at the beach? How could you slow it down?
1. Name the two things iron needs to rust.
2. Why does a bike rust faster at the beach? How could you slow it down?
Teacher note: wear gloves to take the steel wool out, wrap it in newspaper for the bin, and pour the liquids down the sink. Everyone washes their hands.
Show what we know
The summative lesson, run as a celebration. Each child makes a change detective poster about four changes from the term, two reversible and two irreversible. For each change the poster shows what happened, whether it can go back, and the evidence: a measurement, such as the mass of the salty water, or a sign, such as a new gas or a new colour. Children gallery-walk each other’s posters, sit the final check alone, and close with the on-screen quiz as a class game.
We are learning to
- compare reversible and irreversible changes, using evidence from our investigations,
- explain that irreversible changes such as cooking and rusting make new substances,
- show what we know on our own on the final check.
Success criteria
- My poster sorts four changes correctly, each with a piece of evidence from this term.
- I can show on the final check how reversible and irreversible changes are different.
You need
- A3 paper and coloured pencils, and the worksheets from Lessons 1 to 9 for evidence,
- the poster planning sheet (next sheet) and the final check (third sheet), one each per child,
- the interactive unit open for the closing quiz.
Lesson flow (about 60 minutes)
| 5 min | Brief Set the task: four changes, two of each kind, each with its evidence. Ask: “Which investigation gave you the strongest evidence? Which change will you choose for it?” |
| 20 min | Plan and make Children plan on the sheet, then make the poster, with one before-and-after drawing. |
| 10 min | Gallery walk Half the class stands by their posters while the other half visits, then swap. Ask: “What is the evidence for this change? Would it convince someone who was not here?” |
| 15 min | Final check Hand out the final check. Children work alone. Read each item aloud once; help with reading, not with answers. |
| 10 min | The class quiz Run the unit quiz on the board as a whole-class game (see the box). Ask: “One last time: what is the question we ask of every change?” |
Running two half-sessions instead? End Session A after making the posters. Start Session B with the gallery walk, then the final check and the class quiz.
Watch for these ideas
- A change with no evidence. Ask: which lesson showed this, and what did we see or measure?
- “Reversible means it happens fast.” Ask: can the starting material come back?
- An irreversible change with no new substance named. Ask: what new substance was made, and what was the sign of it?
Make it easier, make it bigger
- Easier: choose one reversible and one irreversible change, each with its evidence.
- Bigger: add a fifth change that has a reversible and an irreversible part, such as a burning candle, and explain both.
Answers and look-fors
- Final check marking guide: 1 melting butter. 2 the mass was the same before and after dissolving, and the salt came back when the water evaporated. 3 evaporate the water. 4 from water vapour in the air, which condensed on the cold cup; they are clear, so they did not come through the cup. 5 bubbles of gas when bicarb soda meets vinegar. 6 the runny white sets into a solid, a new substance, and no cooling turns it back into a raw egg. 7 the salt water jar: salt speeds up rusting, so cars near the beach, where the air carries salt, rust faster. 8 any way that keeps water and air off the iron, such as drying it and wiping it with oil, painting it, or storing it in a dry shed.
- A score of 6 or more out of 8, plus a poster that sorts four changes with evidence, meets the descriptor. The rubric near the front of the pack turns this into a level.
- Meeting the idea sounds like “melting chocolate is reversible because it sets again and it is still chocolate, but baking a cake is irreversible because new substances form and it can never become batter again”.
My change detective poster
| The change | Reversible or irreversible? | Our evidence, and the lesson it came from |
|---|---|---|
| 1. | ||
| 2. | ||
| 3. | ||
| 4. |
Before and after
Show what we know
Show what you know about reversible and irreversible changes. Read each one, then circle or write. Take your time.
Teacher note: read the items aloud one at a time. The marking guide is on this lesson’s plan; the rubric near the front of the pack turns the score into a level.