In short
Cut a lemon, mash the inside, add baking soda — the citric acid reacts with the bicarbonate to release CO₂ bubbles.
Halve a lemon, scoop the flesh, add baking soda — and watch chemistry happen.
What you'll learn (or build)
- An acid + a base produces a salt, water and a gas
- Lemon juice contains citric acid
- Baking soda is a base (sodium bicarbonate)
What you'll need
Materials
- 2 Lemons optional
- 3 tbsp Baking soda
- Liquid food colouring
Tools
- A butter knife
- A small spoon
- A tray to catch fizz
Step-by-step
-
1
Halve the lemon ⏱ 1 min
Cut a lemon in half across the middle.Tip: An adult should do the cutting. -
2
Mash the inside ⏱ 2 min
Use a butter knife to mash the lemon flesh until juicy. -
3
Add baking soda ⏱ 1 min
Sprinkle baking soda on top — it will start to fizz immediately.Tip: Add slowly for the longest reaction.
The science behind it
The citric acid in lemon juice reacts with sodium bicarbonate to produce sodium citrate, water and carbon dioxide. The CO₂ bubbles you see escape the liquid as foam.
What kids learn
- Acid-base reaction
- Gas formation
- Hands-on chemistry vocabulary
Try these variations
Frequently asked questions
Can I use vinegar instead?
Yes — vinegar reacts more vigorously but smells stronger.
Why doesn't it work?
Either the lemon is too old (low acid) or the baking soda is too old. Use fresh ingredients.
From parents who tried this
No reviews yet — be the first to share your experience.