Dear belMarduk: if your son likes to do simple experiments, here is one about glass he might enjoy. Prince Rupert (let your son look him up) was a scientific dilettante, and is credited with discovering that if a glass rod is melted in a burner flame, and allowed to cause drops of molten glass to fall into the water, the resulting "tadpoles" have the peculiar property of breaking into tiny pieces if the tail is broken.

http://www.thecure.com/robertpages/princerupertsdrops.html