* Physical Properties are characteristics that can be observed or measured without changing the substance's chemical composition. Examples include color, density, melting point, and boiling point.

* Chemical Properties describe how a substance reacts with other substances or how it changes its composition. Examples include flammability, reactivity with water, and ability to rust.

When sodium metal reacts with water, it undergoes a chemical change:

1. Sodium (Na) reacts with water (H₂O) to form sodium hydroxide (NaOH) and hydrogen gas (H₂). This is a chemical reaction where the original substances are transformed into new ones.

2. The reaction releases heat and can be quite vigorous, sometimes even explosive.

Since the reaction involves a change in chemical composition and the formation of new substances, it's classified as a chemical property.