Dry yeast (found in the baking section of the grocery store)
Liquid dish soap
3% hydrogen peroxide
Large tub or tray to catch the foam
Location for the activity that can tolerate spills (of hydrogen peroxide as well as possibly food coloring), such as a kitchen or bathroom—or an outdoor location
Liquid food coloring (optional)
Different-shaped bottles or glasses (optional)
Put on your safety glasses to do this activity because hydrogen peroxide can irritate your eyes. (Note: although the product of this activity resembles toothpaste, it is not toothpaste, so do not attempt to use it!)
Gather your materials in the location where you plan to do your activity. Place your plastic bottle on the tray or tub so that it is easy to clean up all the foam.
Measure 1/2 cup of hydrogen peroxide, and carefully pour it into the bottle.
Add a big squirt of dish soap into the bottle, and swirl gently to mix.
If you want to make your foam a single color, add a few drops of food coloring directly into the hydrogen peroxide, and swirl the bottle gently to mix. If you want to give your foam stripes like some toothpastes, put the drops along the inside rim of the bottle’s mouth. Let them drip down the inside of the bottle, but do not mix.
In a measuring cup mix together one tablespoon of yeast and three tablespoons of warm water. Stir for about 30 seconds.
Pour the yeast mixture into the bottle then quickly step back, and watch your reaction go! What happens? How long does the reaction last?
Extra: Try the activity without the dish soap. What happens? How was the result different?
Extra: Try the activity with different-shaped containers. What happens if you use a bottle with a narrower or wider neck—or a cylindrical drinking glass with no neck?