Monday, July 30, 2012

Elephant Toothpaste

Recently Helen, who teaches at Papakura Normal School, asked us about this classic experiment. 
There are lot of instructions around on the web but we have tried to make it as simple as we can so you can get this impressive demonstration into your classroom.  So… here’s …

  • What you’ll need
  • How to set it up
  • How to do the experiment
  • The science behind it

What you’ll need:

There are a couple of ways to do this experiment.  The method outlined below uses ingredients that kiwi teachers can get hold of. 

  • 100ml 6% Hydrogen Peroxide (This stuff is used for bleaching hair and for harshly cleaning cuts and grazes. Just ask for it at the chemist, around $7)
  • 1 Tablespoon active yeast
  • 3 Tablespoons of warm water
  • 1 Tablespoon of washing up liquid
  • Food colouring
  • A small drink bottle (we use a 350ml bottle)
  • A tray, to catch the mess.
  • Goggles and rubber gloves (anyone closer than a metre will need these)
  • Small measuring cup and droppers are useful.

How to set it up:

  1. Mix the yeast with the warm water. Stir well so there is no lumps and it let stand for a few minutes.
  2. Prepare your bottle.  Pour all the Hydrogen Peroxide into the empty bottle. Add the washing up liquid and gently shake.
  3. Now drop in the food colouring so it pours down the sides.  This will give it toothpaste stripes.

How to do the experiment … safely …

This experiment is perfectly safe but remember that you are using bleach. Don’t flick or splash it around.  Follow the advice on the container if you get it on your eyes or on your skin.  Anyone closer than a metre should wear safety glasses and rubber gloves.

  1. Put the tray on the table
  2. Place the bottle with the hydrogen peroxide and washing up liquid mixture in the centre of the tray
  3. When everyone is ready - pour the yeast mixture into the bottle and quickly stand back
  4. Watch the reaction!
  5. Everything can be washed up in the sink.  Dry it off so it’s good to go again!

The Science!

The Hydrogen Peroxide is made up of two elements (hydrogen and oxygen).  It is represented by H2O2 and this molecule has four atoms.  This molecule is very close to water, represented by H2O.

Hydrogen Peroxide as a material is very unstable.  It’s decomposing and this is a very slow process.  However, when we add the yeast mixture this acts as a catalyst and speeds things up.  The Hydrogen Peroxide (H2O2) breaks down and becomes water (H2O) and the bubbles in the foam are full of oxygen (O2). The yeast mixture has not changed much, apart from begin diluted by the water. 

Below is a picture of what we used, it all came from the chemist and the supermarket.  Everything here probably comes to around ten bucks which is totally worth it for the reaction you’ll get from your kids.  If you do this experiment why not chuck it on YouTube and send us the link?

We love to be helpful.  If you’ve stuck on how to do an experiment, contact us and we’ll try and help out.

1 comment:

  1. Our Advanced Chem class did this on a larger scale, check out the video here:


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