I seen this on pinterest a while ago so I thought I would try it out with the boys. All you need is a bar of Ivory soap and a microwave safe dish.
Take your bar of soap and cut it in thirds. Then take one of the thirds and cut that in thirds as well. You do not want to put the whole bar of soap in your microwave! So once you have your three little pieces of soap put them on a plate and microwave for abou 30 seconds.
If you have a clear window in your microwave its fun to watch the soap expand. Our door window has a black meshy kind of thing in it so its hard to see though. But when you open the door after the 30 seconds youwill see this!
Doesn't that look like fun? Be careful because the soap will be very hot, even in the middle where all the hot steam is trapped so don't let the kids touch it yet.
After you take it out of the microwave you can put it onto a cookie sheet and used a fork or knife and break the soap up. It will crumble really easy and makes a great playing agent. My boys got out their loaders and dump trucks and went to work hauling the 'snow' around.