1. Phase Changes
Notes 3.3

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

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

5. 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

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

7. 1. Melting
Solid changes to liquid
Endothermic change

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

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

10. 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

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

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

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

14. 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