1. Phase Changes in Matter

2. Review of States of Matter
Solid:
Particles of solids are tightly packed, vibrating about a fixed position.
Solids have a definite shape and a definite volume.

3. Review of States of Matter
Liquid:
Particles of liquids are tightly packed, but are far enough apart to slide over one another.
Liquids have an indefinite shape and a definite volume.

4. Review of States of Matter
Gas:
Particles of gases are very far apart and move freely.
Gases have an indefinite shape and an indefinite volume.
Compressible

5. The Six Phase Changes

6. What is a phase change?
Conversion of the organization of molecules in a substance without changing the individual molecules themselves, such as changing from a solid to liquid or liquid to gas.
All substances experience phase change
A physical change.

7. Freezing Freezing: Liquid to Solid
Heat leaves the liquid as it freezes.

8. Heat goes into the solid as it melts.
Melting…
Melting:
Solid to Liquid
Heat goes into the solid as it melts.
Melting Point: the temp. at which a substance changes from a solid to liquid
The higher the M.P., the larger the attractive force between particles in the substance

9. Heat goes into the liquid as it vaporizes.
Vaporization
Vaporization:
Liquid to Gas
Heat goes into the liquid as it vaporizes.
Boiling Point: temp. at which a substance changes from liquid to a gas
Evaporation: liquid to gas below the substances boiling pt; particles are ejected at surface into air

10. Heat leaves the gas as it condenses.
Condensation
Condensation:
Gas to Liquid
Heat leaves the gas as it condenses.
A substance may condense below its boiling pt.

11. In a refrigerator, a pair of phase changes keeps the food cold.
Evaporator
Energy released to surroundings
Condenser
Energy removed from food compartment
Compressor

12. Warm-Up/Review
1. When a substance is melting, it starts as a ____________ and turns into a _____________.
2. What is the difference between vaporization and evaporation? (hint – look at definitions)
3. When a substances starts as a gas and turns into a liquid, it is called _____________________.
4. When a substance freezes, it starts as a ___________ and turns into a ______________.
5. Is the melting point of a substance an intensive or extensive property?

13. Sublimation and Deposition
Solid to Gas (no liquid phase)
Example: Dry ice
Deposition:
Gas to Solid
Example: Frost forming on windows.

14. Energy and Phase Change
All phase changes require energy. The temperature of the substance remains constant until the phase change is complete.
Any energy used to change phase is no longer available to change the temperature.
Energy can either be used for phase changes or temperature changes, not both!

15. Heating Curve

16. Cooling Curve