* Physical Properties are characteristics of a substance that can be observed or measured without changing the substance's chemical composition.

* Chemical Properties describe how a substance reacts with other substances or changes its chemical composition.

When a substance changes state (solid, liquid, gas), the molecules themselves remain the same. Only the arrangement and movement of the molecules change. For example, water (H₂O) is still water whether it's ice, liquid water, or steam. The chemical formula hasn't changed.

Here are some examples to illustrate:

* Melting ice: Ice (solid water) melts into liquid water. The chemical composition (H₂O) remains the same.

* Boiling water: Liquid water boils into steam (water vapor). Again, the chemical composition is unchanged.

Let me know if you have any more questions!