All lessons › Kitchen chemistry: fizz, foam and fountains › Lesson 6
Australian primary science · Years 5–6 · Lesson 6 of 8
Cola and mint fountain
Inquiry question: Is a cola and mint fountain a chemical change?
Check practical materials
Observing
What students learn
Not all fizzing is a chemical change. In a cola fountain, gas that was already dissolved escapes very fast; no new substance is made.
Success criteria
- I can measure the fountain height from a safe distance.
- I can compare diet cola and soda water using the same method.
- I can explain why bubbling doesn’t always mean a new substance.
Preparation and materials
Before this lesson: Bubbles as evidence (lessons 3 and 5).
- 1.25 L bottles of diet cola — 2
- 1.25 L bottle of soda water — 1
- Mint lollies (the soft, pitted kind) — 1 packet
- Paper tube or index card to drop the mints — 1
- Tape measure or a wall with marks every 50 cm — 1
- Chalk or rope to mark a safety line — 1
- Safety glasses for the teacher — 1 pair
Teacher setup
- Choose a flat outdoor spot away from windows and cars; mark a safety line 5 metres away.
- Mark heights on a wall or pole behind the bottle.
Safety and adaptations
- Teacher demonstration only: students stay behind the safety line, at least 5 metres away.
- Do it outside, away from windows and people walking past.
- The teacher wears safety glasses and steps away quickly.
- Don’t drink the cola afterwards.
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.
- Predict: which will make the higher fountain, soda water or diet cola? Why?
- Watch the soda water fountain. Estimate the highest point using the marks. Record it.
- Watch the diet cola fountain with the same number of mints. Record its height.
- Compare: what was the same and what changed?
- Was any new substance made? What evidence do you have?
- Compare with bicarb and vinegar. What is different?
Teacher modelling prompt
Teacher demonstration outdoors: stand the soda water bottle on flat ground in front of the height marks. Load 5 mints in a paper tube over the opening. Ask for predictions. Release and step back. Students call out the highest mark. Repeat with diet cola. Ask: “Did the drink make a new gas, or let out gas that was already there?”
Record and explain evidence
Recording question: Is a cola and mint fountain a chemical change?
| Drink | Fountain height (m) | What I observed | New substance? Evidence |
|---|---|---|---|
| ________________ | ________________ | ________________ | ________________ |
Example recording headings; record actual observations, including inconclusive results.
Discussion prompt
What evidence would we need to prove a new substance formed, and do we have it?
Check understanding
What should pupils know? Is the cola fountain a physical or a chemical change?
Explain with evidence: Soda water is just water and carbon dioxide, and it also made a fountain. What does this tell us?
Apply the idea: Why does a warm soft drink go flat faster than a cold one?
Teacher answer guidance and saved classroom work are available through the main lesson experience where supported.