1. Topic: Vapor Pressure

2. 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

3. Click here and go over slides from Wisc-Online before talking notes!

4. 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 forces
between it’s molecules

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. Boiling Point Temperature at which:
VP liquid = external atmospheric Pressure
Normal Boiling Point:
temp at which VP liquid = 1 atm
1 atm = standard atmospheric pressure (what we are feeling here in NY)

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

10. > < 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
>
<