1. Click here and go over slides from Wisc-Online before talking notes!
Topic: Liquids & Vapor Pressure Do Now: Compare I2 and F2 Why is F2 a gas at room temp. and I2 a solid
Click here and go over slides from Wisc-Online before talking notes!

2. Vapor
Vapor is the gas phase of substance that is normally liquid at room temperature
Some evaporation occurs at all temperatures
(like you saw with the ice cube)
The easier a substance evaporates, the weaker the IMF

3. Fig a: open system
Evaporation continues until all liquid is gone
Fig b: closed system
Rate of evaporation = rate of condensation
System appears static due to equilibrium

4. How does evaporation occur?
molecules in liquid phase have range of KE;
some have enough KE to “escape” from liquid phase

5. Vapor Pressure Pressure exerted by vapor over its liquid
VP is affected by temperature:
higher the T, higher
the VP

6. Vapor Pressure VP does NOT depend on how much liquid is present
VP depends only on temperature

7. all liquids: as T ↑ the VP ↑
Boiling Point

8. Boiling Point Temperature at which: VP liquid = external atmospheric P
Normal Boiling Point:
temp at which VP liquid = 1 atm
Substances with high bp’s have strong IMF’s

10. Boiling vs. Evaporation
occurs at surface of liquid (or solid)
occurs at all T
liquid cools off as evaporates
spontaneous all the time
BOILING
occurs throughout liquid
occurs at definite T
occurs at constant T
only spontaneous when VP = external pressure

11. > < Boiling and Pressure
If increase external pressure (ex: camping in Death Valley), boiling point is ____ than 100oC
If decrease external pressure (ex: eating Raman noodles at top of Mt. Whitney), the boiling point is ____ than 100oC
>
<

12. IMF in Liquids WEAK FORCES High VP High rate evaporation Low bp
STRONG FORCES
Low VP
Low rate evaporation
High bp

13. Strong or Weak attractive forces?
High vapor pressure
High boiling point
Low boiling point
Low vapor pressure
Evaporates rapidly
Evaporates slowly
Weak
Strong