* Chemical Change: Involves the formation of new substances with different chemical compositions. For example, burning wood creates ash, carbon dioxide, and other substances.

* Physical Change: Alters the form or appearance of a substance but not its chemical composition.

When you break glass, you are simply changing its shape and size. The chemical composition of the glass (silicon dioxide, sodium oxide, calcium oxide, etc.) remains the same.

Here's a helpful way to think about it: You can potentially put the broken pieces of glass back together and get the original piece of glass. This wouldn't be possible if the change were chemical.