Exploding Soap

Let's make some foaming soap in the microwave. Do you think all soap brands will work? Let's see.

ATTENTION: You should have adult supervision when using the microwave.

What You Need

  • Ivory soap bar (and bars of other brands)
  • Paperplate
  • Microwave

What You Do

  1. Unwrap a bar of Ivory™ soap and cut it in half.
  2. Place half the the bar of soap on a paper towel.
  3. Microwave your soap for 90 to 120 seconds and see what happens. A longer length won't make a difference.
  4. The soap will grow!
  5. Let the soap cool. It will feel flaky.
  6. Try other brands. Do they work the same?

The Science. Foams trap gas inside the structure such as styrofoam or shaving cream. When you heat the soap, it softens. The air and water trapped inside the soap vaporizes and expands to become foam. Ivory soap works the best because it is made with a process that locks in air. Think about how popcorn works.

Charles' Law - The volume of a gas increases with its temperature.


Use the following resources to learn more:

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