1

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…

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Partial Pressure

• (Whiteboard)

3

Liquids vs. Gases

Property Gases Liquids

Compress?

Container?

Density?

Mixing?

4

Properties of Liquids

• Vapor Pressure• Heat of Vaporization• Boiling Point

• Viscosity• Surface Tension

5

Liquids – Physical Properties

Substance Vapor Pressure (20°C)

Boiling Point (°C)

Heat of Vaporization(kJ/mol)

MercuryWaterBenzeneEtherEthane

0.001217.575

44227,000

357100

8035

-89

5941312615

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Liquid Properties (Hvap, BP, VP)

Hvap

BP

(boi

ling

poin

t)VP(vapor pressure)

Low

H

igh

High High

High Low

Hig

h

Low

Low LowLow

Low

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Vapor Pressure of Water

• Look at Figure 15.12, pg 411.– H2O VP @20.0 °C

______________ mmHg

– H2O VP @ 36.7 °C ______________ mmHg

• About a 30 mmHg difference, about 4% extra gas volume…

O2 Gas&

H2O Vapor!

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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

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Intermolecular Forces

• IMF is how the molecules stick together.

– Solid: stuck– Liquid: loosely stuck– Gases: unstuck

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IMF – How does it work?

• Dipole Forces– Head – to – tail (Figure 15.5)– Requires that both molecules be polar

(have dipoles)

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IMF – How does it work?

• Induced Dipole Forces– Whiteboard!

• Multiple Names:– London Forces– London Dispersion Forces– Induced Dipole Forces– Dispersion Forces

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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.

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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)

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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?

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Solids

• Crystalline– Salt crystals, diamond, rock candy.

• Polycrystalline– Evian water bottle.– Car windows with polarized glasses!

• Amorphous– Like a milk jug.

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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)

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Polycrystalline (Al2O3)

• The picture is an atomic force micrograph of the sintered surface of apolycrystalline aluminum oxide ceramic. The dark lines separate individualcrystals.  The contrast within each crystal is due to surface facets.