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Elephant Toothpaste

Posted by on February 27, 2011

Sometimes I like to play a little trick on my brother, who doesn’t know anything about chemistry, and get him to mix some chemicals together for me. After getting him to put on some safety gear (gloves and goggles), I tell him to mix two different chemicals together for me. Usually he does it wrong (on purpose probably), but that’s where the trick comes in. If you put too much of one into the other, it almost explodes with tons of foam and steam! It’s a bonus if he gets foam on him, but usually he gets out of the way in time.


Here’s a short video of me testing this reaction out.

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The Science:

The liquid in the large flask is hydrogen peroxide (chemical symbol H2O2) like you can find in the drug store for cuts and scrapes, except the stuff I have is 10 times more powerful! It’s mixed with some ordinary liquid dish soap to give it that green color.

You may have heard water called “H2O” before, and if you have then you already know a bit about chemistry! That tells you that water is made up of 2 parts hydrogen and 1 part oxygen, both gases found in the Earth’s atmosphere. Hydrogen peroxide is a lot like water, as you can see from its chemical symbol H2O2. It’s basically water with another oxygen atom attached to it. That oxygen atom would be much happier if it were a gas rather than stuck onto a water molecule, so it’s easy to break peroxide apart back into water and oxygen.

That’s exactly what I do here. Peroxide breaks down on its own over time, but we can speed it up a lot by adding in another chemical. I’m using potassium iodide (symbol KI) dissolved in water. This greatly speeds up (catalyzes) the peroxide breaking up, which is called a decomposition reaction:

2H2O2 → 2H2O + O2

The oxygen gas (O2) that’s produced blows a lot of small bubbles in the dish soap in solution, which creates a huge amount of foam! The reaction also releases a lot of heat, which is why the foam becomes hot and steams in the air.


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