intermolecular forces

Chapter 12:Intermolecular Forces and

Liquids and SolidsI. States of Matter

a) Kinetic Energy vs. Attractive Forces

II. Intermolecular Forces (Attractive, van der Waal Forces)a) Dipole-Dipole--- (Polar Molecules)

i. Hydrogen Bonding

b) Dispersion (London) Forces--- (NonPolar Molecules)

c) Attractive Forces Involving Ions

Intermolecular Forces and Liquids and Solids

III. Properties of Liquidsa) Viscosityb) Meniscus Formationc) Surface Tensiond) Capillary Action

IV. Phase Changesa) Equilibrium Vapor Pressure

i. Normal boiling point

b) Phase Diagrams

Intermolecular Forces and Liquids and Solids

V. Crystalline Structure of Solidsa) Unit Cells (Simple Cubic, BCC, FCC)

i. Coordination Number

ii. # Lattice Points in a Unit Cell

VI. Radius vs. Unit Cell Edge Length,aa) Density

VII. Types of Crystalline Solidsa) Ionic, Molecular, Covalent, and Metallic

Properties of Liquids

Part III

Properties of Liquid

• Viscosity – Resistance to Flow– Increase Intermolecular Force; Increase

Viscosity– Increase Temperature; Decrease Intermolecular

Force; Decrease Viscosity

Properties of Liquids

Cohesion is the intermolecular attraction between like molecules

11.3

Adhesion is an attraction between unlike molecules

Adhesion

Cohesion

Concave Meniscus of Water

Chemistry; The Science in Context; by Thomas R Gilbert, Rein V. Kirss, and Geoffrey Davies, Norton Publisher, 2004, p 458

Surface Tension1. Attraction of surfacemolecules that cause the liquidsurface to contract and becomemore spherical

2.Amount of energy required to stretch or increase the surface

Consequences of Surface Tension

Chemistry; The Science in Context; by Thomas R Gilbert, Rein V. Kirss, and Geoffrey Davies, Norton Publisher, 2004, p 457

Consequences of Surface Tension

Chemistry; The Science in Context; by Thomas R Gilbert, Rein V. Kirss, and Geoffrey Davies, Norton Publisher, 2004, p 458

CapillaryAction ; Rise of Liquid up a Very Small Diameter Glass Tube

Chemistry; The Science in Context; by Thomas R Gilbert, Rein V. Kirss, and Geoffrey Davies, Norton Publisher, 2004, p 459

Increasing Strength of Intermolecular Force

• Higher Boiling and Melting Point

• Higher Surface Tension

• Higher Viscosity

• Lower Equilibrium Vapor Pressure

Phase Changes

Part IV

Equilibrium Vapor Pressure

• Pressure exerted by gas vapor, in closed container, at a given temperature.

BeforeEvaporation

At Equilibrium

11.8

Why is the Boiling Point of Water Constant ?

Heat

Solid Liquid

Gas

Triple Point

Increasing Temperature

Increasing Pressure

Phase Diagram

Solid Liquid

Gas

Phase Diagram of Water

Solid

Liquid

Gas

Properties of Crystalline Solids

Part V

Simple Cubic Unit Cell

Coordination #

# of Lattice Points Surrounding Each Lattice Point

Simple Cubic Unit Cells

Unit Cell Type Coordinaton # # Lattice Pts In Unit Cell

Simple Cubic 6 1

Body Centered Cubic (BCC)

8 2

Face Centered Cubic (FCC)

12 4

Crystalline Solids Differ in …

1. Lattice Point Representation

2. Type of Force Holding Lattice Point Together

Crystalline Solids

Solid Type Composition Lattice Point Attractive Force

Ionic + & - ions Ion Electrostatic Attraction

Molecular 2 or more nonmetals

Molecule Intermolecular Force

Covalent 2 or more nonmetals

Nonmetal Atom

Covalent Bond

Metallic Metal atoms Metal Cation Metallic Bond

Ionic Crystals

CsCl ZnS CaF2

Molecular Crystals (Ice)

Covalent Crystals

Diamond

Graphite

Metallic Crystals

Properties of Crystalline SolidsSolid Type High Melting

Pt?Conduct electricity as solid?

Conduct electricity dissolved in water?

Ionic YES NO YES

Molecular NO NO NO

Covalent YES NO NO

Metallic YES YES N/A

Crystalline Solids

Solid Type Composition Lattice Point Attractive Force

Ionic + & - ions Ion Ionic Bond

Molecular 2 or more nonmetals

Molecule Intermolecular Force

Covalent 2 or more nonmetals

Nonmetal Atom

Covalent Bond

Metallic Metal atoms Metal Cation Metallic Bond