Phase Changes Notes 3.3

Phase change A reversible physical change from one state of matter to another

During a phase change, ENERGY is absorbed or released Endothermic – energy (heat) is absorbed Exothermic – energy (heat) is released

This might help you... Gas Gas Liquid Liquid Solid Solid Energy is Absorbed Energy is Released Gas Gas Energy Energy Liquid Liquid Energy Energy Solid Solid

Heat of Fusion Amount of energy needed for a substance to change from solid to a liquid It’s another word for melting

1. Melting Solid changes to liquid Endothermic change

2. Freezing Liquid changes to solid Exothermic Doesn’t have to occur at cold temperatures Ex: metals have high freezing points

Note: Most substances have the same melting and freezing point Water melts above 32°F Water freezes below 32°F 32°F

3. Vaporization When a liquid changes to gas Two types of vaporization: 1. Evaporation (occurs below boiling point) 2. Boiling Endothermic – energy (heat) is taken in Ex: Fridge takes heat from air and releases it Heat of vaporization- amount of energy needed to change from liquid to gas

4. Condensation Gas (or vapor) changes to a liquid Exothermic process Ex: Morning dew Exothermic process

5. Sublimation Solid changes to a gas Ex: Dry ice Endothermic process

6. Deposition Gas or vapor changes directly to a solid Exothermic process Ex: Frost forms on windows

This might help you... Gas Gas Liquid Liquid Solid Solid Energy is Absorbed Energy is Released Gas Gas Energy Energy Liquid Liquid Energy Energy Solid Solid