Elephant's toothpaste

My experiment

Watch the experiment here!!

Equipment:

Empty plastic bottle

dry yeast

warm water

liquid dish soap

3% Hydrogen Peroxide (H2O2)

Food colouring

Measuring cups and spoons

Tray

An outdoor location to do the experiment

PPE:

Safety goggles

lab coat

gloves

Warning!! This is not actual toothpaste, so do not use it in your mouth or an animal's mouth. It only looks like it!

Instructions

1. Pour half a cup of hydrogen peroxide into the bottle.

2. Add a generous amount of dish soap to the bottle and swirl gently to mix.

3. Add drops of food colouring along the inside rim of the bottle's mouth. Let them drip down inside the bottle, but do not mix.

4. In a measuring cup, mix 1 tablespoon of yeast and 3 tablespoons of warm water. Stir for 30 seconds.

5. Pour the yeast mixture into the bottle, step back and watch.

Explanation

When the hydrogen peroxide comes into contact with the yeast, it starts breaking down into water and oxygen. The dish soap traps the oxygen gas bubbles, creating a foam. The yeast acts as a catalyst, speeding up the reaction as it contains the enzyme catalase. It neutralises the acidic hydrogen peroxide.

Chemical reaction

hydrogen peroxide (+yeast) = water + oxygen

2H2O2 = 2H2O + O2

It is an EXOTHERMIC reaction as it releases heat during the reaction, causing the bottle and foam to feel warm. An exothermic reaction creates heat and does not require a lot of energy. An endothermic reaction requires heat for a reaction to occur.

Challenge

Can you think of an endothermic reaction you can safely do at home and write it in the comments?

Do you know that Dr Dot did a version of this experiment? Check out her video on YouTube and subscribe to her channel. If you enjoyed this experiment, why not join her online science club where we meet once a month and do experiments, watch TED talks, do pub quizzes and discuss topics such as science in the news! Interested? Join here.