I've seen this super interesting trick involving just Ivory soap and your microwave a few places on the internet lately. My kids were itching for a quick project before dinner tonight, and this was so simple and great for some good, CLEAN fun!
Like any good science experiment, ask your kids to form their hypotheses about what they think will happen to the soap in the microwave. My son H said, "I think it will melt all over the plate." Pop it in the microwave and turn it on for 60-90 seconds (depending on the strength of your microwave, may take longer than 60 seconds to foam up. But it won't explode, so you don't have to worry about that. You may get a little on the side of your microwave as it expands, but it wipes off easily since it's just soap, after all!) Here are my kids watching the soap foaming up and you can see it in the background. (Not to worry, I don't normally let them hang out with their noses pressed to the microwave door!)
Here's the finished product. Doesn't it look cool? The texture is really interesting too and it doesn't feel like cotton candy, even though that's what my kids thought at first!
Next, H wanted to see what would happen if we put food coloring on the soap. This wasn't part of the plan, but we decided to roll with it and check it out. He placed drops of food coloring on the soap, and poked some holes in the soap to get the dye to soak in. H's theory was that it would color the whole soap foam sculpture, like rainbow cotton candy.
Back in the microwave and here are our results. Not as dramatic as we thought, color-wise, but pretty interesting, nonetheless.