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Australian primary science · Year 3 · Lesson 3 of 3
Chocolate change
Inquiry question: Can we melt chocolate and make it solid again?
Check practical materials
Observing
What students learn
Heating melts solid chocolate into a liquid. Cooling turns it back into a solid. The change can be reversed: it is still chocolate.
Success criteria
- I can predict where chocolate will melt fastest.
- I can observe and record how the chocolate changes.
- I can explain that cooling turns melted chocolate solid again.
Preparation and materials
Before this lesson: Students know solids keep their shape and liquids flow (lesson 2).
- Chocolate squares from a block, all the same size — 39 (3 per pair)
- Small zip-lock bags — 39 (3 per pair)
- Plastic cups — 26 (2 per pair)
- Warm tap water — Enough to half-fill 13 cups
- Cold tap water and ice cubes — Enough to half-fill 13 cups
- Paper towel — 13 sheets
- Timer — 1 per pair or the class clock
Teacher setup
- Check the class allergy list. Chocolate contains milk and may contain nuts or soy. If needed, use allergy-safe chocolate, or swap in coconut oil (solid below about 24°C).
- Put one chocolate square in each bag and seal it, pushing out the air.
- Just before the investigation, half-fill one cup per pair with warm tap water and one with cold water and a few ice cubes.
- Print one investigation record per pair.
Safety and adaptations
- Don’t eat the science chocolate: it has been handled by many hands.
- Check allergies first (milk, nuts, soy).
- Use warm tap water only: no kettles or hot water for students. Teacher checks it feels comfortably warm.
- Keep bags sealed so chocolate doesn’t leak.
Review your school policies and curriculum requirements before teaching.
How to investigate
The lesson sequence should leave pupils with evidence to interpret, not only an activity to finish.
- Pairs predict which chocolate will melt first.
- Bag A stays on the desk. Bag B is held in cupped hands (take turns). Bag C floats in the cup of warm water.
- At 2, 6 and 10 minutes, gently squeeze each bag and record: hard, soft or runny.
- Take bag C out, squish it flat into a new shape, then put it in the cup of cold water and ice.
- After 5 to 10 minutes, check bag C. Is it solid again? What shape is it?
- Explain to another pair what heating and cooling did.
Teacher modelling prompt
Hold up three bags. Think aloud: “Bag A stays on the desk. Bag B goes in my hands. Bag C floats in warm water. Same size chocolate, same bags, same time. At 2, 6 and 10 minutes I gently squeeze each bag and write what I notice: hard, soft or runny.”
Record and explain evidence
Recording question: Can we melt chocolate and make it solid again?
| Bag (where it was) | After 2 minutes | After 6 minutes | After 10 minutes | After cooling (bag C only) |
|---|---|---|---|---|
| ________________ | ________________ | ________________ | ________________ | ________________ |
Example recording headings; record actual observations, including inconclusive results.
Discussion prompt
What does our bag C show?
Check understanding
What should pupils know? What made the chocolate melt?
Explain with evidence: Why did bag A on the desk stay hard?
Apply the idea: How could you make chocolate in the shape of a star?
Teacher answer guidance and saved classroom work are available through the main lesson experience where supported.