I started doing this science experiment when my kids were little, so almost 20 years ago.
I had always been under the presumption that the science behind it goes like this ...
Ivory soap is made with natural fats and minerals, including phosphorus.
Fats are acids.
Phosphorus effervesces when in contact with warm acid.
The microwave heats the fats, and that causes the reaction.
However I have recently read that this is not a chemical reaction after all.
It is a physical reaction ...
The whipped condition of the Ivory soap causes it to have air bubbles trapped inside.
As the soap heats in the Microwave, it gets hot and causes the soap to get soft. The
microwaves bouncing around in the oven excite the water and air molecules inside the soap cause them to move in opposite directions from each other and vaporize.
The vaporization of these molecules causes the tiny air pockets or bubbles trapped inside the soap to rapidly expand.
Since the soap has been heated and is in a soft state, the expanding air and water molecules
can easily push it out into a new foam like substance.
I'm not sure which rationale is correct, but I do know it's super fun and gets and smells out of the microwave!!
Check out my video and then try it yourself! I give some little tips on what to do with that fluffed up soap after you are done. Let me know what you discover!