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…

2 Partial Pressure (Whiteboard)

3 Liquids vs. Gases PropertyGasesLiquids Compress? Container? Density? Mixing?

4 Properties of Liquids Vapor Pressure Heat of Vaporization Boiling Point Viscosity Surface Tension

5 Liquids – Physical Properties SubstanceVapor Pressure (20°C) Boiling Point (°C) Heat of Vaporization (kJ/mol) Mercury Water Benzene Ether Ethane ,

6 Liquid Properties (  H vap, BP, VP)  H vap BP (boiling point) VP (vapor pressure) Low  High High  High High  Low Low  Low Low  Low

7 Vapor Pressure of Water Look at Figure 15.12, pg 411. –H 2 O °C ______________ mmHg –H 2 O 36.7 °C ______________ mmHg About a 30 mmHg difference, about 4% extra gas volume… O 2 Gas & H 2 O Vapor!

8 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

9 Intermolecular Forces IMF is how the molecules stick together. –Solid:stuck –Liquid:loosely stuck –Gases:unstuck

10 IMF – How does it work? Dipole Forces –Head – to – tail (Figure 15.5) –Requires that both molecules be polar (have dipoles)

11 IMF – How does it work? Induced Dipole Forces –Whiteboard! Multiple Names: –London Forces –London Dispersion Forces –Induced Dipole Forces –Dispersion Forces

12 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.

13 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)

14 Discussion (Handout) In your team, discuss Figure 15.9, pg Why can we compare the molecules in each trend (H 2 O, H 2 S, H 2 Se, H 2 Te) 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?

15 Solids Crystalline –Salt crystals, diamond, rock candy. Polycrystalline –Evian water bottle. –Car windows with polarized glasses! Amorphous –Like a milk jug.

16 Types of Crystals Based on the bonds! Ionic Crystals (Ionic Bonds) –Salt; Water soluble; High melting points Molecular Crystals (IMF) –I 2 Crystals, Ice Covalent Network Solids (Covalent Bonds) –Diamond & SiO2 (quartz)

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18 Polycrystalline (Al 2 O 3 ) 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.