The Particle Theory of Matter

• All matter is made up of tiny particles.• All particles of one substance are the

same. • Different substances are made of

different particles.• There are attractive forces between the

particles.• There are spaces between the particles• The particles are always moving.

The properties of the States of Matter

Property Solids Liquids Gases

Attractive Forces Between Particles

Strongest Weakest

Amount of Space Between Particles

Smallest Greatest

Motion of Molecules

Least Most

Volume Definite Volume

Definite Volume

No Definite volume

Shape Definite Shape

No definite shape

No definite shape

Degree of Compressibility

Smallest Greatest

Kinetic Molecular Theory Assumptions for Gases

1. Volume of gas molecule is negligible compared to the volume of the container holding the gas

2. Neither attractive nor repulsive forces between gas molecules

3. Gas molecules move in random directions4. Molecular collisions are perfectly elastic.5. The average kinetic energy of gas

molecules is directly related to the temperature.

Changes of State:o Melting – change of state from solid to

liquid.o Freezing – change of state from liquid to

solid.o Evaporation (or Vapourization) – change of

state from liquid to gas.Condensation (or Liquefaction) – change of state from gas to liquid.

o Sublimation – change of state from solid to gas or gas to solid.

Name the change of state

• a) dew forms on grass on a cool summer night.

• b) moth balls placed in a drawer of clothing disappear.

• c) hot liquid butter cools and hardens.• d) ice crystals form on the sides of a

freezer.• e) ice in a glass of pop disappears.• f) frost forms on a car windshield.• g) dry ice disappears in a warm room.

Explain the following using the Particle Theory

• Solids melt when heated.• Changes of state are physical changes.• Gases diffuse (spread out) rapidly.• Your skin feels cool when a liquid

evaporates from it.• The densities of gases are much lower

than those of liquids and solids.• Gases are more compressible than

liquids.

Intermolecular Forces

In the gas phase, these intermolecular forces are negligible and will be ignored!

Gas Pressure

What keeps a balloon inflated?

Pressure = Force

Area

Units…. N/m2 or…

Pascals, Pa

1000 Pa = 1 kPa

Atmospheric Pressure

What keeps the balloon from bursting?

PA = atmospheric pressure!

Bring a pop can tomorrow…. How it works!!

Atmospheric Pressure

Evangelista Torricelli (1608-1647) made accurate measurements of atmospheric pressure using a mercury barometer.

(at sea level) Patmosphere = 101.3 kPa =760 mmHg= 760 torr = 1 atm