The Hydrogen Peroxide and Yeast Chemical Reaction: How Catalase Makes Oxygen Foam

The hydrogen peroxide and yeast chemical reaction produces water and oxygen gas. Yeast contains catalase, an enzyme that speeds up the reaction. The oxygen forms bubbles, and dish soap can trap them in liquid to create foam. The reaction also releases heat, so the mixture may feel warm.

The balanced chemical equation is:

2 H₂O₂ → 2 H₂O + O₂

Catalase speeds the reaction without being consumed in the overall process. The amount of hydrogen peroxide limits how much oxygen can form; the amount and activity of the yeast affect how quickly it forms.

Why yeast causes the reaction

Yeast contains catalase, which helps break down hydrogen peroxide into water and oxygen. Other enzymes, including peroxidases, also act on hydrogen peroxide (NCBI Bookshelf).

Adding more active yeast can make the reaction faster, but it does not increase the total amount of oxygen the hydrogen peroxide can produce. Dish soap does not create oxygen; it helps trap the gas bubbles, making the foam more stable.

Temperature, peroxide concentration, and the condition of the materials can all affect the reaction’s speed and the foam’s height. Warm water can help disperse dry yeast, but water that is too hot can damage the enzyme and reduce its activity.

One example

This demonstration uses household-strength hydrogen peroxide. Wear eye protection, work over a tray or sink, and avoid contact with your eyes or mouth.

1. Pour 50 mL of 3% hydrogen peroxide into a bottle with enough room for foam.
2. In a separate cup, mix 1 teaspoon of dry yeast with 2 tablespoons of warm water. Let it stand briefly so the yeast disperses.
3. If you want more stable foam, add a small amount of dish soap to the peroxide.
4. Pour the yeast mixture into the bottle and observe the bubbles and foam.

The foam may rise quickly, so do not seal the bottle. Keep it upright and away from your face. The reaction’s speed and foam height will vary with the yeast, temperature, peroxide, and container.

What affects the result

More active yeast may speed up the reaction, but the hydrogen peroxide determines the maximum amount of oxygen that can form. More peroxide can allow more oxygen to form, but it does not guarantee a particular foam height.

Use only dilute household peroxide for this demonstration. Concentrated peroxide can cause serious injury and is not suitable for a casual experiment. Check the product label for its concentration and handling instructions.

If little happens, the yeast may be inactive, the water may have been too hot, or the peroxide may have lost strength. Hydrogen peroxide can decompose over time, particularly when exposed to light and heat. Store it in its original, closed container and follow the label’s storage guidance.

Cleanup

Let the foam settle before handling the container. Wash the equipment and any spills with plenty of water, and follow the peroxide label for disposal. Keep peroxide away from eyes, children, and pets. Do not store the yeast mixture and peroxide together; combine them only for the demonstration.

Key Takeaways

• Yeast contains catalase, which speeds the breakdown of hydrogen peroxide into water and oxygen.
• Oxygen bubbles produce foam when trapped in liquid; dish soap helps stabilize it.
• The reaction releases heat, and its speed depends on factors such as temperature, yeast activity, and peroxide condition.
• Use household-strength peroxide, leave the container open, and protect your eyes.
• The amount of hydrogen peroxide limits how much oxygen the reaction can produce.