Fizzy Fun: Elephant Toothpaste

dsc_0899FIZThis was inspired by Lucinda’s excellent post.  I wanted to do it for two reasons.  The first was for its fizzy fun factor!  It was a perfect addition to our Fizzy Fun science.  The second was for the older children to see it happen and for them to design their own experiments using this catalytic reaction as their base.  As they are studying microbes at the moment and had looked extensively into yeast as a type of fungus, I thought investigating its properties as a catalyst might be quite interesting.

The science-y stuff

In this case the yeast acts as a catalyst to speed up the natural decomposition of hydrogen peroxide to oxygen and hydrogen.  Being thermodynamically unstable the heat also aids the process.  This decomposition is an exothermic reaction, meaning that as the reaction progresses the conical flask heats up.



1/2 cup Hydrogen peroxide (found in chemist)

1 tsp Yeast

2 tbsp hot water (not too hot)

1 tbsp Washing up liquid

Conical flask

Tray for catching resulting foam



As I am doing science with a five year old and three year old I like to prepare as much as possible in advance.  It seems to go much more smoothly the less steps they need to do.  Being typical youngsters they just want to see the fun reactive part, not necessarily all the other bits.  As they get older they will do more and more themselves.  I often ask A5 to help with the prep, which she is now old enough to understand and enjoy, unlike B3:


  • A5 measured 1/2 cup of hydrogen peroxide into the comical flask and added the food colouring and washing up liquid.
  • She then mixed the yeast with the water in a test tube and gave it a shake, placing it into a test tube holder.
  • This was all popped into a small cat litter tray.
  • She did this twice, ensuring both she and her sister were able to do the activity separately:


What to do











Of course, I said to go for it!  So they did!












In fact, they spent all afternoon playing with it and only stopped when Daddy came home to take everyone to the leisure centre.  This is definitely one to be repeated…..and often!

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