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Eureka! Elephant’s Toothpaste

Note:  This is the part of a series of posts about science activities to be done in the bathroom – the lav-oratory if you will.  

UPDATE 12/30/15:  Check out the video of this experiment made with Go Ask Mom!

This experiment has been around for a while but it is always fun. This can get messy so you may want to do it in the (empty) bathtub.  When you are done you can fill up the tub and play with the toothpaste while you get clean!

Here’s what you need:

  • 20 or 16 oz soda bottle with a narrow neck
  • Funnel
  • 1/2 cup of Hydrogen Peroxide (Any concentration will work but a higher concentration  will give a more dramatic result.  You can get 3% at the drug store or 6-8% at a beauty supply store.)
  • Dish soap – just a squirt (I used Dawn and it worked great)
  • Couple drops of food coloring (optional)
  • 1-2 teaspoons of yeast dissolved in 2 tablespoons of warm water
  • Safety glasses and clothes (hydrogen peroxide can irritate the skin and eyes so wait until after the reaction to get ready for your bath)
  • A plastic wash basin, cake pan or some other container with sides to hold the toothpaste

Here’s what you do:

  • Use the funnel to pour the hydrogen peroxide and food coloring into the bottle.
  • Add a couple drops of dish soap and switch the bottle around gently to mix everything together.
  • Finally, pour the yeast solution into the bottle and get out of the way!
  • Once the toothpaste stops squirting our of the bottle, feel free to bring it in the bathtub and play.  All you have now is soap, water, oxygen and a little bit of yeast.

Here’s what happens:

Hydrogen peroxide is basically water with an extra oxygen atom – H202.  It is not very stable and slowly decomposes into water and oxygen.  The yeast greatly speeds up or catalyzes the process so that all of the oxygen gas is released very quickly.  The gas gets trapped in the soap creating LOTS of bubble in the soap resembling toothpaste for an elephant or giant.

Feel the bottle during/after the reaction.  It should be quite warm.  The reaction releases quite a bit of energy as well which heats up the solution/foam/bottle.  Reactions that release energy are called exothermic.

So how can you make this into an experiment?  Here are some ideas:

  • How do the results vary when you use different concentrations of hydrogen peroxide?
  • Does the shape or size of the bottle matter?
  • What happens if you just add dry yeast instead of dissolving it in water first?
  •  What happens if you heat up the hydrogen peroxide and soap before adding the yeast?
  • Does the type of soap matter?  Try foaming hand soap, regular hand soap, laundry soap, dishwasher soap or any other liquid soap.