Chapter 11 Liquids and Intermolecular Forces

Sec$on 10.1 Intermolecular Forces Chapter 11 Liquids and Intermolecular Forces

Sec$on 10.1 Intermolecular Forces Intermolecular Forces

Sec$on 10.1 Intermolecular Forces Intermolecular Forces Forces that occur between molecules. Dipole dipole forces Ø Hydrogen bonding London dispersion forces Intramolecular bonds are stronger than intermolecular forces. Copyright Cengage Learning. All rights reserved 4

Sec$on 10.1 Intermolecular Forces Hydrogen Bonding in Water Blue dojed lines are the intermolecular forces between the water molecules.

Sec$on 10.1 Intermolecular Forces Phase Changes When a substance changes from solid to liquid to gas, the molecules remain intact. The changes in state are due to changes in the forces among molecules rather than in those within the molecules. Copyright Cengage Learning. All rights reserved 6

Sec$on 10.1 Intermolecular Phase Changes Forces Solid to Liquid As energy is added, the mo$ons of the molecules increase, and they eventually achieve the greater movement and disorder characteris$c of a liquid. Liquid to Gas As more energy is added, the gaseous state is eventually reached, with the individual molecules far apart and interac$ng rela$vely lijle. Copyright Cengage Learning. All rights reserved 8

Sec$on 10.1 Intermolecular Forces Dipole-Dipole Forces Dipole moment molecules with polar bonds oven behave in an electric field as if they had a center of posi$ve charge and a center of nega$ve charge. Molecules with dipole moments can ajract each other electrosta$cally. They line up so that the posi$ve and nega$ve ends are close to each other. Only about 1% as strong as covalent or ionic bonds. Copyright Cengage Learning. All rights reserved 10

Sec$on 10.1 Intermolecular Dipole-Dipole Forces Orientation of Polar Molecules in a Solid

Sec$on 10.1 Intermolecular Forces Hydrogen Bonding The hydrogen bond is a special dipole-dipole interaction between the hydrogen atom in a polar N-H, O-H, or F-H bond and an electronegative O, N, or F atom. Copyright Cengage Learning. All rights reserved 12 11.2

Sec$on 10.1 Intermolecular Forces Hydrogen Bonding Strong dipole-dipole forces. Hydrogen is bound to a highly electronega$ve atom nitrogen, oxygen, or fluorine. That same hydrogen is then electrosta$cally ajracted to a lone pair on the nitrogen, oxygen or fluorine on adjacent molecules. Copyright Cengage Learning. All rights reserved 13

Sec$on 10.1 Intermolecular London Dispersion Forces Forces Instantaneous dipole that occurs accidentally in a given atom induces a similar dipole in a neighboring atom. Significant in large atoms/molecules. Occurs in all molecules, including nonpolar ones. Copyright Cengage Learning. All rights reserved 14

Sec$on 10.1 Intermolecular Forces Mel$ng and Boiling Points In general, the stronger the intermolecular forces, the higher the mel$ng and boiling points. Copyright Cengage Learning. All rights reserved 15

Sec$on 10.1 Intermolecular Forces The Liquid State

Sec$on 10.2 The Liquid State Liquids Low compressibility, lack of rigidity, and high density compared with gases. Surface tension resistance of a liquid to an increase in its surface area: Liquids with large intermolecular forces tend to have high surface tensions. Copyright Cengage Learning. All rights reserved 18

Sec$on 10.2 The Liquid State Liquids Capillary ac$on spontaneous rising of a liquid in a narrow tube: Cohesive forces intermolecular forces among the molecules of the liquid. Adhesive forces forces between the liquid molecules and their container. Copyright Cengage Learning. All rights reserved 19

Sec$on 10.2 The Convex Liquid Meniscus State Formed by Nonpolar Liquid Mercury Which force dominates alongside the glass tube cohesive or adhesive forces? cohesive forces Copyright Cengage Learning. All rights reserved 20

Sec$on 10.2 The Liquid State Concave Meniscus Formed by Polar Water Which force dominates alongside the glass tube cohesive or adhesive forces? adhesive forces Copyright Cengage Learning. All rights reserved 21

Sec$on 10.2 The Liquid State Liquids Viscosity measure of a liquid s resistance to flow: Liquids with large intermolecular forces or molecular complexity tend to be highly viscous. Copyright Cengage Learning. All rights reserved 22

Sec$on 10.8 Vapor Pressure and Changes of State Vapor Pressure Pressure of the vapor present at equilibrium. The system is at equilibrium when no net change occurs in the amount of liquid or vapor because the two opposite processes exactly balance each other. Copyright Cengage Learning. All rights reserved 25

Sec$on 10.8 Vapor Pressure and Changes of State Vapor Pressure Liquids in which the intermolecular forces are large have rela$vely low vapor pressures. Vapor pressure increases significantly with temperature. Copyright Cengage Learning. All rights reserved 27

Sec$on 10.8 Vapor Pressure and Changes of State Clausius Clapeyron Equa$on P Δ vap, T H vap 1 1 P vap, T R T2 T1 1 ln = 2 P vap = vapor pressure ΔH vap = enthalpy of vaporiza$on R = 8.3145 J/K mol T = temperature (in kelvin) Copyright Cengage Learning. All rights reserved 29

Sec$on 10.8 Vapor Pressure and Changes of State

Sec$on 10.9 Phase Diagrams Phase Diagram A convenient way of represen$ng the phases of a substance as a func$on of temperature and pressure: Triple point Cri$cal point Phase equilibrium lines Copyright Cengage Learning. All rights reserved 32

Sec$on 10.9 Phase Exercise Diagrams As intermolecular forces increase, what happens to each of the following? Why? Boiling point Viscosity Surface tension Enthalpy of fusion Freezing point Vapor pressure Heat of vaporiza$on