I knew the experiment would only work with Ivory but I wanted them to see that.
The reason it works so well is that Ivory has more water and air trapped inside; when heated the water evaporates and the air expands. This turns the bar of soap into a type of foam. Using a paper plate I microwaved part of the Dial soap and we watched it puff up and then melt. Using another paper plate we heated up the Ivory bar.
This is only a physical change as the soap still retains all property of soap, you can wet it and lather it and it would still clean just fine.
In fact as they were getting board playing with the soap in the end I added just a few drops of water to each pile of soap so they could see what happens, and of course I had to ask "is it still soap?" We talked about buoyancy, physical vs. chemical changes, the expansion of air as it heats; very scientific, but I don't think they cared. All they knew was it was cool to watch in the microwave and it was a neat texture to play with.
|Look how huge it's getting!|
|It flakes right back up as they played with it|
We tried our hand at making Borax crystal ornaments. The boys chose which color pipe cleaner they'd like to use and made a fun shape out of it. I suggested spirals, candy canes, green circles (for wreaths), etc. We then boiled up some water, added borax and suspended our ornament shape in the solution. For complete instructions click here. It's hard to capture but they sparkle in the light too.