Last week Cordie thought up a fun  liver and hydrogen peroxide enzyme experiment. The idea is an interesting extension of elephant toothpaste. And it extends the chemistry learning into biology (useful for homeschool records).

When we make elephant toothpaste we use yeast as a catalyst in the breakdown of hydrogen peroxide into water and oxygen gas. By adding soap and food dye, we get oodles of colourful foam that make for a fun and memorable science lesson.

Cordie recently discovered that liver also contains a catalyst which breaks down hydrogen peroxide. She decided to try to inflate a balloon with the gas produced and to test it for oxygen.  (Is it just my kids that love experiments where they get to play with fire?)

You can watch Cordie demonstrating her experiment in the video [4:39] below (with crumpet cameo from Jasper).

What you need

Liver (we used about 200g)

Hydrogen peroxide (we used about 75ml / 1/3 cup of 9% / 30 vol)

Balloon

Small plastic water bottle

Funnel

Peg or clip

Knife

If you want to test for oxygen you’ll also need:

Splint (thin piece of wood)

Lighter/matches

What you do

1. Chop the liver and put it into the bottle

2. Pour the hydrogen peroxide into the balloon via the funnel

3. Carefully put the neck of the balloon over the bottle so that the hydrogen peroxide pours onto the liver

4. Hold the balloon in place as it inflates with gas, then clip it closed

5. If you want to test the gas, light the splint then extinguish the flame. Immediately insert the still-glowing splint into the bottle

 

What happens

As soon as the hydrogen peroxide touches the liver, foam appears and the bottle gets warm. After a few seconds the balloon begins to inflate.

When you lower the glowing splint into the bottle, the flame rekindles. (My kids’ favourite bit!) There should be enough oxygen to do this over and over again.

What’s happening?

Just as with elephant toothpaste, the hydrogen peroxide is broken down into water and oxygen in the presence of a catalyst. (A catalyst speeds up chemical reactions without being changed itself.) The reaction is exothermic – it produces heat.

2H₂O₂ —-> 2H₂O + O₂

 

Liver contains a biological catalyst, the enzyme catalase.

Just as the liver in our experiment breaks down a poisonous chemical into harmless substances, an animal’s liver breaks down toxins and renders them harmless.

Take it further

Heat and cold affect how enzymes work.  In Cordie’s science class she timed her experiments using boiled and frozen liver alongside liver at room temperature.

Further resources

BBC Bitesize – Webpage and video about liver, hydrogen peroxide and enzymes

How to make elephant toothpaste

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Do let me know if you try this. I love hearing from you. 🙂

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