* Chemical Change: Involves the formation of new substances with different chemical compositions. The atoms within the molecules are rearranged.

* Physical Change: Changes the form or appearance of a substance but not its chemical composition. The molecules themselves remain the same.

In the case of water freezing:

* Water (H2O) and ice (H2O) have the same chemical formula. The arrangement of the water molecules changes (from a liquid to a solid state), but the molecules themselves are not altered.

* This change is reversible – ice can melt back into water.

Key takeaway: Freezing is a physical change because it only affects the state of matter, not the chemical makeup of the substance.