* Physical Changes: Alter the form or appearance of a substance but not its chemical composition. They are often reversible.

* Chemical Changes: Result in the formation of new substances with different chemical properties. They are usually irreversible.

In the case of melting ice:

* Water (H₂O) remains water (H₂O) whether it's solid (ice) or liquid (water). The molecules themselves don't change their composition.

* The change is reversible. You can freeze liquid water back into ice.

Key takeaway: Melting ice is a change in the physical state of water, not a change in its chemical makeup.