Chapter 10, Section 2

LIQUIDS

Liquids & Kinetic-Molecular Theory

1. Liquid particles are closer together than gas particles.

Liquids & Kinetic-Molecular Theory

2. More ordered arrangement than gases.

Liquids & Kinetic-Molecular Theory

3. Attractive forces exist between liquid particles. (Remember: this is not true of ideal gases.) These forces hold liquids

together.

FLUID Liquids, like gases,

can flow and therefore take the shape of their container.

Properties of Liquids

1. Relatively high density.

Properties of Liquids

2. Relative incompressibility

Properties of Liquids

3. Ability to diffuse due to constant random motion. Diffusion is slower

than in gases.

Properties of Liquids 4. Surface Tension: a force

that pulls adjacent parts of a liquid’s surface together, thereby decreasing surface area to the smallest possible size.

Capillary ActionThe attraction of the surface of a liquid to the surface of a solid.

GAS vs VAPOR Vapor refers to the

gaseous state of a substance that is normally a liquid or solid at ROOM TEMPERATURE.

VISCOSITYA measure of a liquid’s resistance to flow.

VAPORIZATION

The conversion of a liquid or solid to a gas or vapor

EVAPORATION Process by which

particles escape from the surface of a NONBOILING liquid and enter the gas state.

Only molecules with KE above a certain minimum amount can escape.

COOLING EFFECTS Molecules with highest

KE escape first. Those left behind have

lower KE; temperature of the liquid decreases.

FREEZING: The physical change of a

liquid to a solid by removal of energy as heat.

As a liquid cools, the KE decreases & particles are pulled together in a more orderly arrangement – a solid.

BOILING:Vaporization (appearance of bubbles) throughout a liquid.

VAPOR PRESSURE

The force exerted by the gas above a liquid in a closed container.

Increasing temperature increases vapor pressure

DYNAMIC EQUILIBRIUM

The point when the rate of evaporation equals the rate of condensation.

BOILING POINT The temperature at

which the vapor pressure of the liquid is just equal to the external pressure.

NORMAL BOILING POINT

The boiling point at 101.3 kPa of pressure

INTERMOLECULAR FORCES

Attraction between molecules.

Generally weaker than bonds in a molecule

3 types of IM forces 1. Dipole-Dipole

Forces 2. Hydrogen bonding 3. London Dispersion

Forces

Dipole-Dipole Forces Strongest IM force Occurs between polar

molecules Equal but opposite charges

separated by a short distance creates a dipole.

Hydrogen Bonding A Hydrogen atom that is

bonded to a highly electronegative atom is attracted to an unshared pair of electrons of an electronegative atom in a nearby molecule.

Hydrogen bonding (cont.)

H is small; can get very close to the unpaired electrons

Strong intermolecular force Unusually high boiling

points for molecular compounds

London Dispersion Forces

Electrons are constantly moving – can be distributed unequally.

Creates a temporary dipole

Weak forces

London Dispersion Forces

The IM attractions resulting from the constant motion of electrons and the creation of instantaneous temporary dipoles.

London Dispersion Forces

LDF are present between ALL atoms and molecules.

For NOBLE GASES and NONPOLAR MOLECULES, London Dispersion Forces are the ONLY IM force