Lecture 07 Intermolecular Forces

Lecture 7

Intermolecular Force
Semester 1: 2014-2015
Instructor
Teach Assistants
Office
Office hours

1

Huynh Kim Lam

: Dr. Huỳnh Kim Lâm
: Ms. Võ Diệu Ánh Dương
Ms. Hồ Như Ngọc
: Rm. A1.705
: 9:00-11:00 AM, Thursday (LKH)
Chemistry for Engineers (CH011IU) - Lecture 7 - Semester 1: 2014-2015

[e-mail] / lamhuynh.info

Molecular forces

Intramolecular forces (bonding forces)
– exist within each molecule
– influence the chemical properties of the substance
– are relatively strong (larger charges that are closer together)

Intermolecular forces (nonbonding forces)
– exist between the molecules
– influence the physical properties of the substance
– are relatively weak (smaller charges that are farther apart)
2

Strength

Intramolecular Forces - Review

Copyright @ 2007 by The McGraw-Hill Companies, Inc.

3

Intermolecular forces

 exist between the molecules
 influence the physical properties of the substance
• boiling and melting points, vapor pressures, and viscosities  are relatively weak (smaller charges that are farther apart)

4

Review on physical states

5

Phase changes
Phase changes are also determined by the interplay between kinetic energy and intermolecular forces.
Temperature ↑
→ average kinetic energy ↑
→ faster moving particles can overcome attractions more easily
Condensation: gas → liquid
Vaporization: liquid → gas
Freezing: liquid → solid
Melting, or fusion: solid → liquid
Sublimation: solid → gas
Deposition: gas → solid
6

Heating-cooling curve
A cooling curve for the conversion of gaseous water to ice

Copyright @ 2007 by The McGraw-Hill Companies, Inc.

7

The Equilibrium Nature of Phase Changes (reading)

Liquid-Gas Equilibria
Solid-Liquid Equilibria
Solid-Gas Equilibria
Phase Diagrams: Effect of Pressure and Temperature on Physical State

8

Intermolecular Forces

Four main types:
 Dipole-dipole
 Ion-dipole
 Hydrogen bonding
 London Dispersion force
Not every molecule has all of four types of forces.
Then,