Elephant toothpaste
01 // Question
How does the amount of yeast added change how fast and how high the foam rises?
Yeast contains catalase, an enzyme that speeds up hydrogen peroxide breaking apart without being used up itself.
02 // Variables
Independent
Amount of yeast added- 1 teaspoon
- 2 teaspoons
- 3 teaspoons
Dependent
Foam height and reaction speed- Maximum foam height, cm
- Time to reach it, seconds
03 // Hypothesis
IF the amount of yeast added to the hydrogen peroxide mixture increases, THEN the foam will reach a greater height in less time, BECAUSE more yeast means more catalase enzyme working to break down the hydrogen peroxide at once.
04 // Procedure
1. Mix the base
In a bottle, combine 3% hydrogen peroxide, a squirt of dish soap and a few drops of food coloring.
2. Mix the yeast
Stir yeast into warm water in a separate cup until it dissolves.
3. Start the timer
Pour the yeast mixture into the bottle and start timing immediately.
4. Record height
Note the foam height every 10 seconds until it stops rising.
5. Repeat with more yeast
Reset with a clean bottle and repeat with 2, then 3 teaspoons of yeast.
05 // Data table
| Yeast | Height reached (cm) | Time to plateau (s) |
|---|---|---|
| 1 teaspoon | ____ | ____ |
| 2 teaspoons | ____ | ____ |
| 3 teaspoons | ____ | ____ |
Formula 2 H2O2 → 2 H2O + O2 (catalase speeds up this decomposition without being consumed)
06 // What to expect
More yeast makes the reaction start faster and reach a taller foam column, up to a point — beyond a certain amount, adding more yeast stops making much difference because the hydrogen peroxide runs out first.
The bottle gets warm to the touch, because breaking apart hydrogen peroxide releases heat — this is an exothermic reaction, not just a fizzy one.
07 // Lab notes
- Use only 3% hydrogen peroxide — the kind sold as a household antiseptic, not a stronger lab or salon-grade solution.
- Wear goggles and do this over a tray; the foam is warm and can overflow quickly once the reaction starts.
- Safety. Despite the name, the foam is not edible and not real toothpaste — wash hands after handling.
- Safety. Work in a ventilated area, since the reaction releases a fine oxygen-rich foam mist.
08 // Remember
A catalyst doesn't get used up. It just makes a reaction that was always going to happen go faster.
09 // Questions people ask
Is elephant toothpaste dangerous?
The classroom version made with 3% hydrogen peroxide is low risk with goggles and gloves, but it does get warm and can overflow fast, so keep it on a tray. A stronger, lab-grade version made with 30% hydrogen peroxide is significantly more hazardous and is a demonstration for trained adults, not a student experiment.
What is the catalyst in the elephant toothpaste experiment?
The catalase enzyme in yeast is the catalyst. It speeds up the breakdown of hydrogen peroxide into water and oxygen gas without being consumed itself, which is why a small amount of yeast can process a large volume of peroxide.
Why does the bottle feel warm afterward?
The decomposition of hydrogen peroxide into water and oxygen releases energy as heat, making this an exothermic reaction — that's also why the foam feels warm to the touch right after it forms.