Physical Characteristics of

Gases

The Kinetic Molecular Theory of

Matter

Objectives• List the physical properties of gases

• Use the KMT to explain the physical properties of gases.

Kinetic Molecular Theory of Gases

• KMT- The particles of matter are in constant motion.

Ideal Gas – a gas that behaves according to the kinetic molecular theory.

Kinetic Molecular Theory of Gases1. Gases are made up of

tiny particles.- Usually atoms or

molecules

Kinetic Molecular Theory of Gases2. The particles of a gas are

far apart from each other.

• The volume of gas particles is insignificant relative to the space between the particles

Kinetic Molecular Theory of Gases3. The particles of a gas

are in constant motion and collide with each other and the walls of their container.

• The collisions are elastic; no K.E. is lost.

• Collisions exert a force -pressure

• Specian's Phun machines: Ideal gas – YouTube

Kinetic Molecular Theory of Gases4. The particles of a gas do not exert any force on each

other.

Kinetic Molecular Theory of Gases5. Temperature is a

measure of the average kinetic energy of the particles of a gas.

Kinetic Energy in a Gas - YouTube

2

2

1.. mVEK

Properties of Gases

Expansion of gases

• No definite shape or volume

• Expand to fill their container

Properties of Gases

Fluidity of Gases

• Gases have the ability to flow.

Properties of GasesLow Density

1 mole of H2O @ 20oC: 18 mL

1 mole of H2O @ 120oC and

1 atm: 22.4 L

Properties of GasesCompressibility

• Gases can be easily compressed

Properties of GasesDiffusion and Effusion

Diffusion –mixing of particles due to random motion of particles

Effusion – process in which gases past through a tiny opening

Deviations from Ideal Gas Behavior

At low temperatures and high pressures, gases do not follow ideal gas behavior.

1. The volume of the particles is significant.

2. Intermolecular forces become important.

Real gas – one that does not behave according to the KMT