Now that we had the soap, I couldn't wait to try the experiment. I'm a big kid when it comes to this kind of stuff, and seeing my kids get all excited about it is just that much better! I read a few of the other blog posts about this experiment, there are about a million of them..so just Google it! But based on the recommendations, I decided not to put a whole bar of the soap into the microwave at once. We cut our bar into three pieces. It actually cuts really easily, and I used a butter knife! I also opted to put it on a paper plate. Some sites just said to place it right in the microwave or on a paper towel, but I was still a little weary of exactly what would happen, so I wanted to play it safe with the plate.
Before the soap went into the microwave, we talked about what my son, who's four years old, thought would happen. He claimed it would heat up and turn into a cup. I raised my eyebrow, as I'm sure you just did reading this! And then I asked him what happened when we heat up food in the microwave. He explained it gets hot, but it doesn't turn into a cup. It stays food. But he still kept to his theory that the soap would change to a cup! Oh well, he's imaginative, and I couldn't wait to show him what was actually going to happen!
I also read to microwave it from anywhere from 30 seconds to 3 minutes. Quite a big difference. Really it starts to expand almost immediately, and by 30 seconds it's about as big as it's going to get. I tried to take a few pictures of it expanding in the microwave, but came out too blurry to really be helpful. Make sure you hold your kids up or stand them on a chair (if they're big enough) to watch. Actually seeing it expand is the neatest part of the whole experiment. Well that, and the expression on your kids' faces while it happens! When we opened the microwave door it did deflate a little bit, but as you can see by the picture, it definitely expands quite a bit from being heated up. Another plus, it has a nice clean smell which lingers a while in the kitchen!
The outside of the foamy creation is cool enough to touch, but be careful about squeezing it or playing with it too much right away, because it is still quite warm right out of the microwave. It looks much softer than it actually is too! Once it cooled, it became crumbly and disintegrated into a substance much like the fake snow you can buy around Christmastime. Thank goodness we have a hand-vac to clean up that mess!!
In researching this experiment, I found there are lots of topics to discuss with kids while performing this soap trick. I think 4 years old is a little young to fully understand the chemistry behind it, but we did have fun talking about how the soap changed, touching it, and smelling it. Older kids might enjoy learning more about the chemistry aspect of foams and gases. But we'll wait a few more years for that.