Science demonstrations can be real crowd pleasers. In fact, Camille Schrier won the 2020 Miss America crown after performing a science demonstration during the talent portion of the competition. On stage, she mixed common chemicals to create massive mountains of steaming foam — a trick often called “elephant toothpaste.” It wowed the judges. But as she said when she performed it, this was a demonstration. It wasn’t an experiment. But you can turn that, or any demonstration, into an experiment.
Start by finding a hypothesis. This a statement that you can test. How do you find a hypothesis? You can begin by learning more about how a specific scientific demonstration works. By breaking it down into its parts, you might be able to find a statement to test. And from there, you can design your experiment.
Elephant toothpaste explained
Let’s look at the elephant toothpaste demonstration. There are four ingredients: hydrogen peroxide, dish soap, food coloring and a catalyst. Hydrogen peroxide (H2O2) is a chemical people can use to clean wounds or surfaces and bleach them. It slowly breaks down when exposed to light, forming water and oxygen
This is where the catalyst comes in. A catalyst is something that speeds up a chemical reaction. In the elephant toothpaste experiment, yeast or potassium iodide can be used as a catalyst. Either will cause the hydrogen peroxide to break down very quickly.
The dish soap and food coloring aren’t needed for the reaction. But they create the show. As hydrogen peroxide breaks down into water and oxygen, the dish soap will catch the liquid and gas to form bubbles. It’s the source of the foam. The food coloring gives the foam its bright color.
Now that we know what’s happening, we can start asking questions. How much hydrogen peroxide should you use? How much catalyst? How much dish soap? Those are all good questions. In fact, they’re each the beginning of a hypothesis.
Let’s focus on hydrogen peroxide. If the hydrogen peroxide breaks down into the water and oxygen that power the foam, then perhaps more hydrogen peroxide would produce more foam. That gives us a hypothesis: More hydrogen peroxide will produce more foam.
Demo to experiment
We can now design an experiment to test that hypothesis. First, identify the variable that you will be testing. Here, our hypothesis is about hydrogen peroxide. So the experiment needs to change the proportion of hydrogen peroxide in the elephant toothpaste.
An experiment also needs a control — a part of the experiment where nothing changes. The control could be no hydrogen peroxide (and no foam). The experiment could then test different amounts of hydrogen peroxide to see which produces the most foam.
You will have to measure the outcome of any experiment. For elephant toothpaste, you might measure the height of the foam using video recordings. Or you could measure the mass of your container before and after the reaction, to see how much foam exploded out. This would be different for every experiment. For an experiment involving plants, you could measure plant height or the size of any fruit. When growing rock candy, you could weigh the final product.
Running the experiment just once isn’t enough. You need to repeat it many times, step by step, over and over. Any single result could have been due to some accident. Repeating the experiment again and again cuts the chance you will see a difference by mistake. Write down all the results very carefully. It helps to keep a lab notebook.
Finally, you will want to compare results. This may mean running statistical tests on your data. These are mathematical tests that can help you interpret your findings. They might show you that more hydrogen peroxide does indeed produce more elephant toothpaste. Or the results might show something else. Maybe there’s just the right amount of hydrogen peroxide, and too much doesn’t produce any more foam.
If you want to find out, though, don’t do a demonstration. Test it through an experiment.