Ivory Soap Science Experiment


Easy experiment with Ivory Soap for Kids.  Predict whether a bar of soap with sink or float...then microwave it! Great way to introduce the ideas of solids and gasses.


  • 1 FRESH bar of Ivory Soap

  • 1 Bar of Dove Soap or other brand

  • Clear Container filled with water

  • Tongs or Slotted Spoon (optional)

  • Microwave safe plate

  • Microwave Oven

ivory soap experiment step by step


  • Examine both bars of soap.
  • Predict whether each soap will float or sink.
  • Place one bar of soap at a time to see what happens.
  • Discuss why one might float and the other sink.
  • Cut the Ivory Soap into quarters. (Adult Step)
  • Examine the pieces of soap. Do you see any air pockets or does it look solid?
  • Place the quarters on microwave safe plate.
  • Microwave for 60 seconds.
  • Remove from microwave. The soap will be warm, not hot.
  • Let cool slightly for children to touch.
  • Place broken pieces of soap into small dish for children to wash hands with...it will be very flaky or put in a small mesh bag.

Tips and Suggestions

  • If you have a 1,000 watt or higher microwave, try setting it for 60 seconds first.
  • Be sure to use a fresh bar...one that has been stored on a shelf may not be as effective.
  • If you want to use the soap, save a netted bag from garlic, scallions or little boiler onions and place soap inside!
  • Make sure children wash hands after handling so they don't rub their eyes and get them irritated.
  • Do not leave soap unattended while microwaving. Extra time in the microwave should not cause any melting or damage but you should always monitor anything you put in the microwave.

Educational Notes

What is Happening? Heating the Ivory soap softens it and heats the air and water trapped within the bar of soap. This causes the water to vaporize and the air to expand. The expanding gasses push on the softened soap which causes the soap to expand. The appearance of the soap is changed however no chemical reaction is occurring.

Ivory bar soap is whipped with air in its production and floats in water. Ivory's first slogan "It Floats!" was introduced in 1891. Other brands of soap do not have as much air in it and will not have the same result. We did not test any other brands in the microwave.

Note that your microwave will be very fragrant for a day. Here is our experiment for you to view if you prefer not to try it yourself:

Science Concepts


  • Seeing
  • the soap and the change it goes through
  • Feeling
  • the soap before and after the experiment
  • Smelling
  • the soap


  • Oral
  • Describing or explaining what is happening
  • Pictorial
Using books to help learn about solids and gases