* Physical changes alter the form or appearance of a substance but don't change its chemical composition. In this case, the ice (solid water) changes into liquid water. The chemical formula (H₂O) remains the same.

* Chemical changes involve the formation of new substances with different chemical properties. Melting ice doesn't create any new substances.

Think of it this way: You can freeze the water back into ice, reversing the change. This wouldn't be possible if a chemical change had occurred.