* No new substances are formed: When water freezes, it changes from a liquid state to a solid state. The chemical composition (H₂O) remains the same. The water molecules simply arrange themselves in a more ordered, crystalline structure.

* The change is reversible: You can easily melt ice back into liquid water, returning it to its original state. This reversibility is a key indicator of a physical change.

Contrast this with a chemical change:

* A chemical change involves the formation of new substances with different chemical compositions. For example, burning wood is a chemical change because it produces ash, smoke, and gases, which are different substances from the original wood.

* Chemical changes are usually difficult or impossible to reverse.