* No new substance is formed: When water freezes, it changes from a liquid state to a solid state (ice). The chemical composition of the water (H₂O) remains the same.

* The change is reversible: You can easily reverse the change by heating the ice, which melts it back into liquid water.

In contrast, a chemical change would involve the formation of a new substance with a different chemical composition. For example, burning wood is a chemical change because it produces ash, smoke, and carbon dioxide, all of which are different substances from the original wood.