Topic: Chemistry Aim: Explain the different types of phase changes.

Review: 1.Identify the different phases of matter. 2.The particles of a substance are closest together in a _____. 3.The particles of a substance that does not have a definite volume or shape is 4.Identify an example of a physical change. 5.What are 2 physical properties of matter? 6.Give 1 example of a chemical property.

Phase Changes Involves the absorption or release of heat (energy).

1. Melting Solid  liquid Melting point: temp at which a solid changes to liquid (different for every substance) Substance absorbs heat energy

2. Freezing Liquid  solid Freezing point: temp at which substance changes from liquid to solid Substance loses heat energy

3. Evaporation LIQUID GAS Liquid absorbs heat energy Liquid  gas Boiling point: temp at which liquid boils (d ifferent for every substance)

4. Condensation Gas  liquid LIQUID GAS Gas loses heat energy

5. Sublimation Solid  Gas No liquid phase Ex: dry ice Solid GAS Solid absorbs heat energy

Freezing L  S Melting S  L Evaporation L  G Condensation G  L Add heat  Energy absorbed by molecules Remove heat  Energy released by molecules PHASE CHANGES SOLIDLIQUID GAS

Time TEMPTEMP Freezing/melting point = 0°C Boiling pt = 100°C SOLID LIQUID GAS 100°C 0°C Melting Freezing Evaporation Condensation PHASE CHANGE GRAPH FOR WATER = phase changes

REVIEW: 1. When a liquid becomes a solid, energy ____. 2. ____ is the process in which liquid changes to gas below the boiling point. 3. The change of a liquid to a solid is called__. 4. What happens to the position of water molecules as they lose heat energy? 5. Identify one phase change in which energy is released.

1. Melting Solid  liquid Heat added/absorbed  molecules move faster & farther apart Melting point: temp at which a solid changes to liquid (different for every substance) Substance absorbs heat energy

2. Freezing Liquid  solid Liquid heat energy/energy released  Molecules slow down & come closer together Freezing point: temp at which substance changes from liquid to solid Substance loses heat energy

3. Evaporation LIQUID GAS Liquid absorbs heat energy Liquid  gas Heat added/absorbed (faster & farther) On surface of liquid  evaporation Boiling point: temp at which liquid boils (d ifferent for every substance)

4. Condensation Gas  liquid Gas loses heat energy/energy released (slow down & closer together) LIQUID GAS Gas loses heat energy

Moth balls commonly undergo the process of sublimation. Sublimation is the process in which a solid changes directly to its gaseous phase, skipping the liquid phase.