I've been seeing the Ivory Microwave Experiment on blogs for years and have been meaning to try it. When the girls got ivory soap for soap carving at the art museum, this experiment is the very first thing that came to mind. First I invited L and E (almost 5) to place two different brands of soap in a bowl of water and observe what happens. The Ivory soap floated, and the other brand did not. The girls predicted that it was because it was lighter, but then were not so sure when they felt the weight of both bars in their hands (I should have brought out the scale so we could compare them). I asked some prompting questions to get them thinking about how some objects that are filled with air float...
Then I cut the Ivory soap bar in half and placed one half in the microwave for about a minute. L stood on a chair and observed. My husband was in the room talking to his friend on the phone and the look on his face when I saw me place soap in the microwave was priceless! (afterward he kept opening the microwave and sniffing it)
The result was that the soap expanded (tremendously) in size. The girls made some observations about the changes that occurred, and tried to determine if it was still soap or whether it had changed into something else. I explained to the girls that the soap had air trapped inside of it (which is why it floated), and when air is heated the molecules inside of it move faster and faster bumping into each other and causing it to expand (but remain soap).
The soap foam made for some fun sensory play outside on the deck. The girls mixed it with water to form soap sculptures. We're still waiting for a good thunderstorm to wash all the soap flakes off the deck!
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