Describe burning and rusting as changes that form new materials, and distinguish them from a change of state.
A torn ticket and a rusty bracket both look different.
Did both become a new substance?
Success looks like
Use evidence to distinguish a new substance from a change of shape or state.
Explain why cooling burnt wood or rust does not restore the starting material.
Describe iron rusting and fuel burning without claiming that matter disappears.
Retrieval
GROW · SCIENCE · Lesson 6 of 6
Three things we can recover
R1. How could liquid water become ice?
R2. Does dissolved salt stop existing?
R3. Does melting always make a new substance?
I do
GROW · SCIENCE · Lesson 6 of 6
I ask two different questions
Can a simple process reverse this change?
Is the material still the same substance?
I use the second question to classify the change.
Two questions about a changeDiagram description
Two separate questions distinguish reversibility from substance identity. Melting ice can be reversed by cooling and makes no new substance; tearing paper is difficult to reverse but also makes no new substance.
I do
GROW · SCIENCE · Lesson 6 of 6
I explain the rusty bracket
Iron reacts with oxygen and water.
Rust is a new material.
Cooling does not restore the original iron.
Iron reacts to form rustDiagram description
A word model shows iron and oxygen with water forming rust; this is not a balanced equation and the shapes are labels, not particles.
Continue within this stage’s shared time.
I do
GROW · SCIENCE · Lesson 6 of 6
I separate two candle processes
Melting wax changes its state.
Burning wax vapour makes new substances.
Cooling reverses melting, not burning.
One candle, two different changesDiagram description
A top row shows reversible wax melting and solidifying. A separate bottom row shows wax vapour plus oxygen forming carbon dioxide and water; these chemical products are not turned back into wax by cooling.
Choose a prediction, test the diagram, then explain. Pause or reset at any time. Paper W1–W3 use the same evidence.
Decision 1 of 3
Which pair makes no new substance in our cases?
Two questions about a change
Use substance identity; being hard to undo is insufficient.
Decision 2 of 3
Which explanation best fits the rusty bracket?
Iron reacts to form rust
Cooling or wiping rust does not regenerate the original iron.
Decision 3 of 3
Which result can cooling the remaining liquid wax produce?
One candle, two different changes
Separate the phase change from combustion. Atoms are not destroyed.
All decisions checked. Explain one choice using the evidence, then save your work.
Choose, test, then explain together. Evidence diagrams appear only after your test. Diagram transitions explain the model; they do not represent real elapsed time. Use Pause model to stop transitions and model controls, or your device’s reduced-motion setting. The printed We do activity provides the paper route.
We do
GROW · SCIENCE · Lesson 6 of 6
Repair the workshop rule
W2. Test the rule against torn paper.
Replace it with a better decision question.
Which case supports your new rule?
Continue within this stage’s shared time.
We do
GROW · SCIENCE · Lesson 6 of 6
Two labels for one candle
W3. Label E-A and E-B separately.
Which part can cooling reverse?
Where does the burnt wax material go?
Melting: state change. Burning: new substances, including gases.
Continue within this stage’s shared time.
Hinge
GROW · SCIENCE · Lesson 6 of 6
Which is the strongest evidence?
A sample looks different after a change.
Which fact most supports a chemical change?
You do
GROW · SCIENCE · Lesson 6 of 6
Write a workshop diagnosis
Choose one response route.
Classify with evidence and explain rusting or burning.
Make a label a younger visitor can understand.
You do
GROW · SCIENCE · Lesson 6 of 6
Use a cause, not only a description
“It turned brown” describes an observation.
What new material formed?
What reacted to produce it?
Continue within this stage’s shared time.
You do
GROW · SCIENCE · Lesson 6 of 6
Check the two-change trap
Have you separated wax melting from burning?
Have you avoided “everything disappears”?
Use one accurate reason per diagnosis.
Continue within this stage’s shared time.
Review
GROW · SCIENCE · Lesson 6 of 6
Audit the diagnosis
Share privately, with a partner, or with the teacher.
Underline the evidence for a new substance.
Correct one misleading rule.
Review
GROW · SCIENCE · Lesson 6 of 6
Choose the next exhibit
Should the workshop show rusting or candle changes?
Explain which would clear up a misconception.
We will use one reason to improve the display.
Continue within this stage’s shared time.
Exit
GROW · SCIENCE · Lesson 6 of 6
Leave a reliable label
E1. Why is rusting a chemical change?
E2. Why can torn paper still be physical?
E3. What is different about wax burning?
Slide 1
GROW SCIENCE · Change detectives: what became something new?
1 • Shared evidence: workshop cases
Constructed teaching cases. Use these for W1–W3; no practical experiment is required.
A • Ice tray
Ice warms into liquid water. Cooling below its freezing point makes ice again.
B • Paper ticket
A ticket is torn into pieces. Tests identify the pieces as the same paper material.
C • Iron bracket
After days in moist air, a brown coating forms. Analysis identifies rust, a new material.
D • Wood offcut
Burning forms ash and gases. Cooling the products does not restore the wood.
E • Candle wax
A: solid wax melts. B: wax vapour burns with oxygen, forming carbon dioxide and water.
Rule to audit
“If I cannot put it back easily, it must be a chemical change.”
W1. Sort A–D: new substance / no new substance. Explain one choice.
W2. Repair the rule using case B.
W3. Classify E-A and E-B. Which change can cooling reverse?
GROW SCIENCE · Change detectives: what became something new?
2 • Supported route: diagnosis cards
Use page 1. Circle, label, draw or dictate. Word bank: oxygen / water / rust / new.
S1. Rusting makes …
☐ A new material
☐ Only smaller pieces of iron
S2. Complete: Iron reacts with ____ and ____ to form ____ .
S3. Melting ice is a physical change because …
☐ The substance is still water
☐ All changes involving heat are chemical
S4. Explain why tearing paper does not prove a chemical change.
S5. Write two candle labels: one for melting and one for burning. Include “new substance” in one label.
GROW SCIENCE · Change detectives: what became something new?
3 • Standard route: repair report
Use evidence, not just appearance. A short sentence or labelled diagram is enough.
Case
Physical or chemical?
Evidence
Ice melts
Paper tears
Iron rusts
Wood burns
N1. Complete the classification table.
N2. Explain why rusting is not reversed by simply cooling the bracket.
N3. A visitor says wax melting and burning are the same. Write a two-sentence correction.
N4. Explain why some products of burning are missing from an open tray.
GROW SCIENCE · Change detectives: what became something new?
4 • Stretch route: test a tempting rule
Two claims need careful correction. No chemical equation is required.
Claim A: “Every change that is hard to undo forms a new substance.” Claim B: “Only 2 g of ash remained from 10 g of dry wood, so 8 g of matter was destroyed.” These masses are a constructed teaching example from an open system.
T1. Use a counterexample to evaluate claim A. Give a better classification rule.
T2. Explain claim B’s error. Include gases and oxygen from the air. Why can we not calculate the total gas mass as simply 8 g?
T3. Design two contrasting exhibit labels for wax melting and burning, explaining the role of cooling.
GROW SCIENCE · Change detectives: what became something new?
5 • Exit and reflection
Work independently. Use science words where helpful.
E1. Explain why rusting is a chemical change.
E2. Why can tearing paper be a physical change even if it is difficult to restore?
E3. Give one difference between wax melting and wax burning.
E4. Where can some burning products go in an open system?
Reflection. Which workshop claim would you now challenge, and why?