A physical property is one in which there is no change in the chemical composition of a substance. Boiling point only changes the physical appearance of the substance without changing its chemical structure or molecular composition. For example, the boiling point of water changes water from a liquid phase to water vapor, which is a gas phase. But the chemical composition of both water and water vapor are the same (H2O). No chemical bonds are broken or formed during the change. The molecules simply move further away from each other, which results in the change of phase. Boiling point is considered an intensive physical property because it does not depend on the amount of the substance. A small quantity of water has the same boiling point as a large quantity of water.