* No new substances are formed: The wax simply changes state from liquid to solid, and the water remains water. There's no chemical reaction creating new molecules.

* The composition of the wax and water remains the same: The chemical makeup of the wax doesn't change, it just becomes more compact as it solidifies.

* The change is reversible: You can melt the solidified wax again, returning it to its liquid state.

Key takeaway: Physical changes involve a change in form or appearance, but not a change in the fundamental chemical composition of the substances involved.