Section 12-3

A change in matter from one form to another is known as phase change. There are four main kinds. A substance always loses or gains heat as it changes phases.

A change from a solid phase to a liquid form. At a solid’s melting point, the solid gains enough heat to change to a liquid.

A change from a liquid phase to a gas form. At a liquid’s evaporation point, the liquid gains enough heat to change to a gas.

A change from a gas phase to a liquid form. At a gas’s condensation point, the gas loses enough heat to change to a liquid.

A change from a liquid phase to a solid form. At a liquid’s freezing point, the liquid loses enough heat to change to a solid. Freezing point of water is 0 0 C or 32 0 F.

Section 12-4

Chemical ChangePhysical Change Changes that produce new substances. Chemical changes are burning, rusting, digestion, burning of gasoline in an engine. Changes that do not produce new substances. Physical properties are mass, weight, volume, density, phases of matter, shape, size, taste, color, smell, texture. Physical changes are cutting an apple in half, crumpling up a piece of paper.