All lessons › Kitchen chemistry: fizz, foam and fountains › Lesson 3
Australian primary science · Years 5–6 · Lesson 3 of 8
Bicarb meets vinegar
Inquiry question: What happens when an acid meets a base?
Check practical materials
Observing and testing
What students learn
When an acid and a base react, new substances form, including carbon dioxide gas, and the acid is used up so the pH moves towards neutral.
Success criteria
- I can describe what happens when bicarb and vinegar react.
- I can use pH results to show the acid was used up.
- I can give more than one piece of evidence that a new substance formed.
Preparation and materials
Before this lesson: Acids and bases with indicator strips (lesson 2).
- White vinegar — 2 bottles
- Bicarbonate of soda — 1 box
- Clear plastic cups — 13
- Teaspoons — 13
- pH test strips — 1 pack
- Rulers — 13
- Safety glasses — 26
- Trays — 13
- Dishwashing liquid (for the demonstration) — 1 bottle
Teacher setup
- Put each cup on a tray to catch overflow.
- Pour 1/4 cup of vinegar into each cup.
Safety and adaptations
- Wear safety glasses: vinegar stings eyes.
- Never seal bicarb and vinegar in a closed container: the gas can burst it.
- Don’t taste anything.
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.
- Put on safety glasses. Test the vinegar with a strip. Record the pH.
- Add 1/2 spoon of bicarb. Measure the highest foam. Record what you notice.
- When the fizzing stops, test the pH again. Record it.
- Repeat: add 1/2 spoon at a time, measuring foam and pH, until adding bicarb no longer fizzes.
- What happened to the pH each time?
- List your evidence that a new substance formed.
Teacher modelling prompt
Stir a spoon of dishwashing liquid into a cup of water to make foam. Show how to hold a ruler beside the cup and read the top of the foam at eye level, and how to dip a strip and match the chart. Say: “Same measurements every time you add a spoon.”
Record and explain evidence
Recording question: What happens when an acid meets a base?
| Bicarb added (spoons) | Highest foam (cm) | pH after fizzing | What I noticed |
|---|---|---|---|
| ________________ | ________________ | ________________ | ________________ |
Example recording headings; record actual observations, including inconclusive results.
Discussion prompt
Which two pieces of evidence best support Claim B?
Check understanding
What should pupils know? Name two new substances made when bicarb and vinegar react.
Explain with evidence: Why did the pH get closer to 7 as more bicarb was added?
Apply the idea: Why might someone take an antacid tablet for a sore stomach?
Teacher answer guidance and saved classroom work are available through the main lesson experience where supported.