Page 58 - BBC Knowledge - October 2017 IN

Science
Experiments

ELEPHANT WHAT’S GOING ON?
‘Elephant toothpaste’ isn’t toothpaste at all,
TOOTHPASTE but a foam of oxygen bubbles that have
been ensnared by the washing-up liquid
and thickened by the glycerine.
METHOD: Chemically, hydrogen peroxide is made of two
1. This experiment is messy! Either work at a table that’s easy hydrogen atoms and two oxygen atoms (H2O2).
to clean, or head outside. This makes it similar to water (H2O) but with
2. The dried yeast needs to be rehydrated to ‘activate’ the microbes. an extra oxygen atom (O) – yet hydrogen
Thoroughly mix two or three tablespoons (or one sachet) of yeast peroxide is poisonous to living things, which is
YOU WILL NEED: with some warm water in a bowl. Leave for a couple of minutes why we use it as a disinfectant, and why

l Safety glasses while you get everything else ready. we keep it away from our mouths and eyes.
l Gloves 3. Put on gloves and safety glasses. Yeast, however, carries a protective enzyme
l Washing-up liquid 4. Pour half a cupful of hydrogen peroxide into the bottle (more if called catalase that destroys hydrogen
l Dried yeast (make sure that it has not you’re using a larger bottle). peroxide. The moment the living yeast cells
expired) 5. Add a good squirt of washing-up liquid. touch the liquid disinfectant, the enzymes go to
l Warm water 6. Pour in up to two tablespoons of glycerine. work tearing the hydrogen peroxide molecules
l Food colouring 7. You are going to be making toothpaste, so why not add some food apart, into water and oxygen. The oxygen
l Empty 500ml plastic drinks bottle colouring? I drizzled some orange food colouring down one side of bubbles up vigorously to form a rapidly growing
l 9% hydrogen peroxide (this is a mild the bottle and blue down the other. foam that erupts from the top of the bottle, such
skin disinfectant that you can buy over 8. Pour the (now activated) yeast into the bottle using the funnel. is the fervour of the reaction.
the counter at pharmacies) 9. Stand back as the bottle erupts with a thick foam that seems to just You can try this science demonstration
l Funnel keep on going. It looks like toothpaste, but it’s definitely not for with liver instead of yeast, as this organ
l Glycerine (find this in the baking section brushing teeth with! also contains enzymes that destroy
of the supermarket, or in bigger bottles hydrogen peroxide.
at a pharmacy)

!

SAFETY
NOTES
Hydrogen peroxide can
irritate eyes and sensitive skin, so
wear safety glasses and gloves.
Do not swallow hydrogen
peroxide or splash
in eyes.

58
OCTOBER 2017