16 Feb 2013 60 Comments
“Elephant’s toothpaste” is a wonderful illustration of the power of a catalyst to speed up a reaction. It’s also very cool, and anything that shows kids how cool science is worth doing, right?
What You Need
- 6% Hydrogen peroxide (1/2 cup)
- Yeast (1 tsp)
- Hot water (2 tbsp approx) in a small dish
- Food colouring
- Washing-up liquid (dish soap)
- Empty soda/water bottle (small)
- Tray to stand the bottle on to catch the foam
- Funnel (optional)
What You Do
- Pour the hydrogen peroxide into the bottle
- Mix the yeast into the water
- Add the washing up liquid and food colouring to the hydrogen peroxide in the bottle
- Add the yeast mixture to the bottle
- Stand back and admire the reaction!
The photos say it all! We had enough hydrogen peroxide in our £2.74 bottle to have two goes. Afterwards I gave the children a bowl each to mix up the red and green foam.
The Scientific Explanation
Hydrogen peroxide naturally breaks down over time into water and oxygen. Catalase, the enzyme in yeast, acts as a catalyst to speed up the reaction.
The washing-up liquid joins with the oxygen to make an abundance of foam. And – as with so many of our homeschool science projects – the food colouring just makes the whole thing look even cooler!
What We Might Do Differently Next Time
I get so excited doing experiments like this that there are always a few things I forget to mention to the kids. (But that’s ok because then we have an excuse to do it again. :-))
I would point out next time that during the reaction, the bottle gets warm and steam is produced from the water, because this is an exothermic (heat-producing) reaction.
I would also mention that although a catalyst speeds up a chemical reaction, it is left unchanged itself: the dissolved yeast is left in the bottle.
The Book and the Hat-Tip
Elephant toothpaste is well set-out in our favourite Science Experiments book, but I followed the instructions I found at another mum’s blog (unfortunately her blog is no longer live). Where there’s a choice, I prefer to follow a mum’s personal experience when it comes to learning fun with kids!
Do you notice our safety glasses? Not strictly necessary here, but they definitely remind us we’re Real Scientists!
For more fun science ideas, visit Science Sunday at Adventures In Mommydom.