At-Bristol's Live Science Team has a wonderful video series of experiments that can be done with inexpensive materials available at typical hardware, kitchenware, and grocery stores, like turning water into instant ice.
You may know this as a quick way to chill wine and beer quickly, but kids will have fun making slushy stalagmites using this simple trick with salt and ice. Nucleation points!
Below is an interesting episode about refractive indices, showing how to make items invisible using pyrex and glycerol.
