2.  A change of state is the conversion of a substance from one state to another  All changes of state are physical changes  The identity of a substance does not change

3.  During a change of state, the energy of a substance changes  The energy of a substance is related to the motion of its particles  If energy is added to a substance, its particles move faster  If energy is removed from a substance, its particles move slower

4.  The temperature of a substance is a measure of the speed of its particles  This means temperature is a measure of the energy of a substance  A transfer of energy, known as heat, causes the temperature of a substance to change and can lead to a change of state

5.  Melting is the change of state fro a solid to a liquid  The melting point of a substance is the temperature at which the substance changes fro a soli to a liquid  Most substances have a unique melting point that can be used with other data to identify them  Melting point is a characteristic property of a substance

6.  For a solid to melt, particles must overcome some of their attraction to each other  When a solid is at its melting point, any energy it absorbs increases the motion of its atoms or molecules  Melting is an endothermic change because energy is absorbed

7.  Freezing is the change of state from a liquid to a solid  The temperature at which a liquid changes from a liquid to a solid is it freezing point  Freezing and melting occur at the same temperature  Freezing is an exothermic change because energy is removed from the substance

8.  Vaporization is the change of state from a liquid to a gas  Boiling is vaporization that occurs throughout a substance  The temperature at which a substance boils is called its boiling point  Boiling point is a characteristic property of a substance

9.  Evaporation is vaporization that occurs at the surface of a liquid below its boiling point  When you perspire, your body is cooled by the process of evaporation  Evaporation also explains why water in a glass on a table will disappear after a few days

10.  Condensation is the change of state from a gas to a liquid  The condensation point of a substance is the temperature at which the gas becomes a liquid and is the same temperature as the boiling point at a given pressure  Condensation is an exothermic change

11.  Sublimation is the change of state from a solid directly into a gas  Frozen carbon dioxide (dry ice) will change from a solid directly to a gas  The molecules must go from being very tightly packed to being very spread apart  Sublimation is an endothermic change