The boiling point of a substance is a physical property. A physical property of a material or substance is one that can be observed without changing or altering the composition of the material. Examples are mass, Density, Color, solubility, boiling point, melting point . A chemical property of a substance is one that describes how the material changes into a completely different substance and is observed only during a chemical reaction. Examples of chemical properties include types of chemical bonds, heat of combustion, reactivity with other metals, oxidation state and enthalpy of formation.