1. Follow along in your text Chapter 11 Sections 3 & 4 Pages 393 - 405
Energy of State Changes & Equilibrium
Follow along in your text Chapter 11 Sections 3 & 4 Pages

2. Phase Changes

3. Phase Changes Evaporation
molecules at the surface gain enough energy to overcome IMF
Volatility
measure of evaporation rate
depends on temp & IMF

4. Phase Changes Equilibrium
trapped molecules reach a balance between evaporation & condensation

5. Phase Changes temp v.p. IMF v.p. Vapor Pressure
pressure of vapor above a liquid at equilibrium
v.p.
depends on temp & IMF
directly related to volatility
temp
temp
v.p.
IMF
v.p.

6. Phase Changes Patm b.p. IMF b.p. Boiling Point
temp at which v.p. of liquid equals external pressure
depends on Patm & IMF
Normal B.P. - b.p. at 1 atm
Patm
b.p.
IMF
b.p.

7. Phase Changes IMF Melting Point Melting Point equal to freezing point
Which has a higher melting point?
polar or nonpolar?
covalent or ionic?
polar
ionic

8. Phase Changes Sublimation solid  gas
Vapor pressure of solid equals external pressure
EX: dry ice, mothballs, solid air fresheners

9. Heating Curves Gas - KE  Boiling - PE  Liquid - KE  Melting - PE 
Solid - KE 

10. Heating Curves Phase Change change in arrangement of molecules
temp remains constant
Heat of Fusion (Hfus)
energy required to melt 1 gram of a substance at its melting point

11. Heating Curves Heat of Vaporization (Hvap)
energy required to boil 1 gram of a substance at its b.p.
usually larger than Hfus…why?
EX: sweating, steam burns, the drinking bird

12. Phase Diagrams
Shows the phases of a substance at different temps and pressures.
See Pgs.402 & 403

13. Phase Diagrams Triple Point
Temperature & pressure at which all 3 phases of matter exist at the same time
Critical Point
Temperature & pressure at which the liquid & vapor phases are the same