* Physical properties can be observed or measured without changing the chemical composition of the substance.

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

When a substance boils, it changes its state from liquid to gas, but the molecules themselves remain the same. The boiling point simply represents the temperature at which the vapor pressure of the liquid equals the surrounding atmospheric pressure.

In summary:

* Boiling point is a characteristic of a substance that can be measured without altering its chemical makeup.

* It describes a physical change (liquid to gas) and not a chemical change.