1. Changes of State
Section 4.3

2. What are Changes of State?
Physical Changes
Reversible changes
Examples:
Melting
Freezing
Sublimation
Deposition
Condensation
Vaporization

3. Energy, Temperature & Changes of State
Energy is always involved in changes of state.
Mater either loses or absorbs energy when it changes state.
Temperature – the average kinetic energy of the particles of matter.

4. Changes Between Liquids and Solids
Freezing – liquid changing into a solid
Liquid particles lose energy until they no longer slide past each other.
Once in a fixed position they become a solid
Freezing point – the temperature at which a liquid changes into a solid
Example: Water 0°C (32°F)

5. Melting Melting – when solid changes into a liquid.
Melting point – the temperature at which a solid changes to a liquid.
Melting point is the same as the freezing point.
Heat of fusion - the amount of energy required to change a substance from the solid phase to the liquid phase at its melting point

6. Changes Between Liquids and Gases
Vaporization – liquid changes to a gas
point at which the liquid breaks free of all attractive forces and changes into a gas
2 ways
evaporation (happens at the surface of the liquid) particles break away into the air without boiling
boiling (throughout entire substance)

7. Boiling point Heat of vaporization
the temperature at which the pressure of the vapor in the liquid is equal to the external pressure acting on the surface of the liquid
Heat of vaporization
the amount of energy required for the liquid at its boiling point to become a gas

8. Condensation Condensation – gas changes to a liquid
Water vapor cools, loses energy, forms droplets
Examples: fog on bathroom mirror

9. Changes Between Solids and Gases
Sublimation – solids change directly to a gas (without going through being a liquid)
Example: Dry ice

10. Deposition
Deposition – gas changes directly to a solid without going through the liquid state.
Example: frost

11. Heating Curve or PHASE DIAGRAMS
Temperature remains constant during a change in state.