Little Scientists: The Incredible Expanding Soap

April 15, 2020

A fun science experiment that only needs three items to execute! What will happen when you put Ivory soap in the microwave? (Besides a nice smelling kitchen.)


  • A bar of Ivory soap (other bar soaps don’t work)
  • Microwave
  • Large microwavable plate


1. Cut soap in half or quarters depending on how large you want your soap souffle to be. (If you’re going to use a whole bar, it helps to shave off some of top layer for a faster result.)

2. Place soap in the middle of a very large microwavable plate.

3. Microwave soap from 30 seconds to 1 minutes depending on its size. For our whole bar we microwaved it for a little over a minute. You can play with the soap afterwards, but please allow a bit of time to cool.

But why?

The expanding effect is caused by the heating of the water that is inside the soap. The water vaporizes, forming bubbles; the heat also causes trapped air to expand. Likewise, the heat causes the soap itself to soften and become pliable. This effect is actually a demonstration of Charles’ Law.

– from the scientific mind of Miss Jen

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