View Page Gallery

KS2 Science at Home: week 8

Key Stage 2 Experiment of the Week! – Elephant toothpaste!

How does it work?
As you can see from the picture, foam will overflow from the bottle, so be sure to do this experiment on a washable surface, or place the bottle on a tray.


The foam is special because each tiny foam bubble is filled with oxygen. The yeast acted as a catalyst (a helper) to remove the oxygen from the hydrogen peroxide. Since it did this very fast, it created lots and lots of bubbles. The experiment created a reaction called an exothermic reaction, which means it not only created foam, it created heat! The foam produced is just water, soap, and oxygen, so you can clean it up with a sponge and pour any extra liquid left in the bottle down the drain.

The experiment can also be done with the hair care version of hydrogen peroxide, or the weaker pharmacy version, although the effect with the pharmacy version will be smaller. Safety goggles should be used adults should read instructions on containers for safety precautions.

Materials you need

  • A clean 16-oz plastic soda bottle
  • 1/2 cup 20-volume hydrogen peroxide liquid (20-volume is a 6% solution; you can get this from a beauty supply store – or online)
  • 1 Tablespoon (one packet) of dry yeast
  • 3 Tablespoons of warm water
  • Liquid dishwashing soap
  • Food colouring
  • Small cup
  • Safety goggles 


1. Hydrogen peroxide can irritate skin and eyes, so put on those safety goggles! An adult should carefully pour the hydrogen peroxide into the bottle.

2. Add 8 drops of your favourite food colouring into the bottle.

3. Add about 1 tablespoon of liquid dish soap into the bottle and swish the bottle around a bit to mix it.

4. In a separate small cup, combine the warm water and the yeast together and mix for about 30 seconds.

5. Now the adventure starts! Pour the yeast water mixture into the bottle (a funnel helps here) and watch the foaminess begin! 

Some research for next week: Which came first, the rubber egg or the rubber chicken?

We will answer this question with next week’s science experiment!