Chapter 15.1 – 15.8
• Partial Pressure
– (Whiteboard)
• Liquids vs. Gases
• Liquid Properties
– Vapor Pressure, Heat of Vaporization, Boiling Point
– Viscosity, Surface Tension
• Intermolecular Forces
• Selected Properties of Solids
• NOTE: Be sure to prepare for tomorrow – it’s
somewhat tough…
1
Partial Pressure
• (Whiteboard)
2
Liquids vs. Gases
Property
Gases
Liquids
Compress?
Container?
Density?
Mixing?
3
Properties of Liquids
• Vapor Pressure
• Heat of Vaporization
• Boiling Point
• Viscosity
• Surface Tension
4
Liquids – Physical Properties
Substance
Vapor Pressure
(20°C)
Mercury
Water
Benzene
Ether
Ethane
0.0012
17.5
75
442
27,000
Boiling Point
(°C)
Heat of
Vaporization
(kJ/mol)
357
100
80
35
-89
59
41
31
26
15
5
Liquid Properties (Hvap, BP, VP)
Hvap
6
Vapor Pressure of Water
• Look at Figure 15.12,
pg 411.
– H2O VP @20.0 °C
______________ mmHg
– H2O VP @ 36.7 °C
______________ mmHg
O2 Gas
&
H2O Vapor!
• About a 30 mmHg
difference, about 4%
extra gas volume…
7
Intermolecular Forces
• Recall:
– Bond Polarity is bases on the electronegativity
difference:
H-F
H
H
O
– Molecular Polarity
• Net effect of bond dipoles, “swimming”
– Movie with gas Pressure/Temperature diagram
• Motion of the molecules in solids/liquids/gases
8
Intermolecular Forces
• IMF is how the molecules stick together.
– Solid:
– Liquid:
– Gases:
stuck
loosely stuck
unstuck
9
IMF – How does it work?
• Dipole Forces
– Head – to – tail (Figure 15.5)
– Requires that both molecules be polar
(have dipoles)
10
IMF – How does it work?
• Induced Dipole Forces
– Whiteboard!
• Multiple Names:
– London Forces
– London Dispersion Forces
– Induced Dipole Forces
– Dispersion Forces
11
IMF – How does it work?
• Hydrogen Bonds
– These are special!
– Requires that you have N-H, O-H, of F-H in
the molecules
– Get a very strong IMF between the
molecules.
12
IMF – How does it work?
• What makes a IMF Strong?
– Hydrogen bond is the strongest
– Dipole-Dipole is generally stronger with
stronger dipoles (EN)
– Induced dipole (dispersion) is strongest
with big, fat atoms (low on PT)
13
Discussion (Handout)
•
In your team, discuss Figure 15.9, pg 407.
1. Why can we compare the molecules in each
trend (H2O, H2S, H2Se, H2Te)
2. Which molecules are polar?
3. Which molecules are not polar?
4. Explain why the lines increase for the last 3
molecules. (which IMF, why)
5. Explain why the red line is higher than black
which is higher than blue. (which IMF, why)
6. Identify the effect of Hydrogen bonding. How
does this figure make it obvious?
14
Solids
• Crystalline
– Salt crystals, diamond, rock candy.
• Polycrystalline
– Evian water bottle.
– Car windows with polarized glasses!
• Amorphous
– Like a milk jug.
15
Types of Crystals
• Based on the bonds!
• Ionic Crystals (Ionic Bonds)
– Salt; Water soluble; High melting points
• Molecular Crystals (IMF)
– I2 Crystals, Ice
• Covalent Network Solids (Covalent Bonds)
– Diamond & SiO2 (quartz)
16
17
Polycrystalline (Al2O3)
• The picture is an atomic
force micrograph of the
sintered surface of a
polycrystalline
aluminum oxide
ceramic. The dark lines
separate individual
crystals. The contrast
within each crystal is
due to surface facets.
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