1. Intermolecular forces and phase diagrams
Ms. Hoang ACP Chemistry

2. review
Name three intermolecular forces in the order of strongest to weakest
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Intramolecular forces (aka chemical bonds) are stronger/weaker than intermolecular forces
Intermolecular forces are responsible for the chemical/physical properties of a compound

3. Three phases Phases Solid: fixed shape and volume
Liquid: fixed volume but takes shape of container
Gas: no definite volume or shape

4. Phases

5. Phase changes What kind of process is this (hint: think energy)
_____________: Solid  Liquid
_____________: Liquid  Gas
_____________: Solid  Gas
_____________: Gas  Liquid
_____________: Liquid  Solid
_____________: Gas  Solid
What kind of process is this (hint: think energy)
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What kind of process is this (hint: think energy)
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6. Dynamic equilibrium Rate of phase changes are all equal
States of Matter PhET
Rate of phase changes are all equal

7. Vapor Pressure
Vapor Pressure: the pressure exerted by a vapor in equilibrium with its liquid phase at a certain temperature
HIGH vapor pressure
volatile
weak/strong intermolecular forces?

8. Practice problems Which substance is MORE volatile? Why? H2O vs. H2S
H2O vs NaCl
CH4 vs HCl

9. Boiling point and vapor pressure
What is happening when water boils?
H2O molecules need enough energy to break intermolecular forces and go from liquid to gas
Can water boil at temperature other than 100oC?

11. Vacuum pump demo
Youtube video:

12. Heating curve for water
q=mc∆T
Temperature

13. Phase/phase changes depends on two variables
Summary
Phase/phase changes depends on two variables
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14. Phase diagram
Graph showing Temperature and Pressure at which different phases are in equilibrium
Label phases: Solid, Liquid, Gas
Triple Point: where all three phases are in equilibrium
Critical Point: where gas and liquid phases become indistinguishable
Critical pressure: pressure above which the liquid phase of a substance cannot exist
Critical temperature: temp above which gas cannot be liquified
Normal freezing point: temperature at which substance changes phase to a solid at P=1atm
Normal boiling point: temperature at which vapor pressure of liquid = atmospheric pressure (1atm)