Get into the spooky spirit with this foamy chemical reaction! Our foaming halloween pumpkin is a fun end or alternative to pumpkin carving.

foaming halloween pumpkinYou will need:

  • Carved pumpkin
  • Cup x 2
  • Spoon
  • Dried yeast
  • Washing up liquid
  • Hydrogen peroxide (available from most chemists/pharmacies)


  • *An adult should do this* Fill one cup 1/4 with hyodrogen peroxide
  • Squirt some washing up liquid into the hydrogen peroxide
  • Place the cup inside the pumpkin.
  • In the other cup, put 2 tsp of dried yeast and fill to half way with water
  • Stir the mixture, it might smell a little!
  • Pour the yeast mixture into the hydrogen peroxide and quickly put the lid on the pumpkin.
  • Watch it foam!
foaming halloween pumpkinThe science bit: Your foaming halloween pumpkin is actually a very simple chemical reaction. Hydrogen peroxides chemical formula is H2O2, like water (H2O) but with more oxygen. When you mix it with yeast, it reacts and splits into H2O (water) and O (oxygen). The water mixes with the washing up liquid and foams up and the bubbles are full of oxygen. If you touch it, you should notice that is feels hot. This is called an exothermic reaction, it creates heat!

Why not try:

  • Adding some paint or food colouring to the hydrogen peroxide next time to make a colourful foam!
  • It doesn’t have to be a pumpkin! Why not try a foaming watermelon?
Like this experiment? Check out more experiments like this on our blog!

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