* Physical Changes: Alter the form or appearance of a substance, but not its chemical composition.

* Chemical Changes: Result in the formation of new substances with different chemical compositions.

When you crush a rock, you're simply changing its size and shape. The chemical makeup of the rock remains the same. It's still the same minerals, just in smaller pieces.

Here are some examples to further illustrate:

* Physical Change: Crushing an ice cube (still H₂O)

* Chemical Change: Burning wood (changes to ash, carbon dioxide, etc.)

Let me know if you have any more questions!