This Elephant Toothpaste Recipe Is Safe for Kids

This Elephant Toothpaste Recipe Is Safe for Kids

2019-12-25 13:02:38

The elephant toothpaste demo foams up like an elephant squashed a giant tube of toothpaste. Here's a kid-friendly recipe for this classic project.

The elephant toothpaste demo is one of the most popular chemistry demonstrations, in which a steaming tube of foam keeps erupting from its container, resembling a smooshed tube of elephant-sized toothpaste. The classic demo uses 30% hydrogen peroxide, which is not safe for kids, but there is a safe version of this demonstration that is still very cool.

Materials

  • Empty 20-ounce plastic bottle (or other container)
  • 3% hydrogen peroxide solution (available at nearly any store)
  • Packet of active yeast (from the grocery store)
  • Liquid dishwashing detergent (such as Dawn™)
  • Warm water
  • Food coloring (optional, but it looks nice)

Make Elephant Toothpaste

  1. Pour 1/2 cup hydrogen peroxide solution, 1/4 cup dishwashing soap, and a few drops of food coloring into the bottle. Swish the bottle around to mix the ingredients. Set the bottle in a sink or outdoors or some other place where you won't mind getting wet foam everywhere.
  2. In a separate container, mix a packet of active yeast with a little warm water. Give the yeast about 5 minutes to activate before proceeding to the next step.
  3. When you are ready to do the demo, pour the yeast mixture into the bottle. The reaction occurs immediately upon the addition of the yeast.

How It Works

Hydrogen peroxide (H2O2) is a reactive molecule that readily decomposes into water (H2O) and oxygen:

In this demonstration, yeast catalyzes the decomposition so it proceeds much more rapidly than normal. Yeast need warm water to reproduce, so the reaction won't work as well if you use cold water (no reaction) or very hot water (which kills the yeast.)

The dishwashing detergent captures the oxygen that is released, making foam. Food coloring can color the film of the bubbles so you get colored foam.

In addition to being a nice example of a decomposition reaction and a catalyzed reaction, the elephant toothpaste demo is exothermic, so heat is produced. However, the reaction just makes the solution warmer, not hot enough to cause burns.

Christmas Tree Elephant Toothpaste

You can easily use the elephant toothpaste reaction as a holiday chemistry demonstration. Just add green food coloring to the peroxide and detergent mixture and pour the two solutions into a Christmas tree-shaped container.

A good choice is an Erlenmeyer flask because it has a cone shape. If you don't have access to chemistry glassware, you can make a tree shape by inverting a funnel over a glass or making your own funnel using paper and tape (which you could decorate, if you like.)

Comparing the Original Reaction With the Kid-Friendly Recipe

The original elephant toothpaste reaction, which uses a much higher concentration of hydrogen peroxide, can cause both chemical burns and thermal burns. While it produces a larger amount of foam, it's not safe for kids and should be performed only by an adult using proper safety gear.

From a chemistry perspective, both reactions are similar, except the kid-safe version is catalyzed by yeast, while the original demonstration is usually catalyzed using potassium iodide (KI). The kid's version uses chemicals that are safe for children to touch.

The lower concentration of peroxide can still discolor fabrics. Care should be taken to avoid ingestion because the project includes detergent, which can cause vomiting.

Key Takeaways

  • The elephant's toothpaste chemistry demonstration produces heated foam when chemicals are mixed.
  • The original demonstration results from decomposition of hydrogen peroxide catalyzed by potassium iodide. Detergent solution captures gases to form the foam. The kid-friendly version uses a lower concentration of hydrogen peroxide, with the decomposition catalyzed by yeast.
  • While both versions of the reaction may be performed for a young audience, the original version uses concentrated hydrogen peroxide, which is a strong oxidizer, and potassium iodide, which may not be readily available.
  • The kid-friendly version uses chemicals that are safe for children to touch, in case of a splash.
  • As with all chemistry demonstrations, adult supervision is recommended.

Sources

  • Dirren, Glen; Gilbert, George; Juergens, Frederick; Page, Philip; Ramette, Richard; Schreiner, Rodney; Scott, Earle; Testen, May; Williams, Lloyd. Chemical Demonstrations: A Handbook for Teachers of Chemistry. Vol. 1. University of Wisconsin Press, 1983, Madison, Wis.
  • "Elephant's Toothpaste." University of Utah Chemistry Demonstrations. University of Utah.