The Nature of Gases

List 5 Properties of Gases

Kinetic Molecular Theory of Gases

• This is the six point model that is used to explain the behavior of gases

Points of the Kinetic Molecular Theory

• 1. Gases are composed of atoms or molecules that have mass

• 2. Gases are in constant, random, straight line motion

• 3. The particles that make up a sample of a gas are separated from each other by great distances

• This is why the volume is NOT FIXED

Continuing the points

• 4. Gas particles collide with each other and the container that they are in

• All of these collisions result in a transfer of energy from particle to particle

• Or from particle to surroundings• No energy is ever lost completely

and these are called ELASTIC COLLISIONS.

Continuing

• 5. Gas particles have no attraction for each other

• 6. Gases are highly sensitive to changes in temperature and pressure

How is an “ideal” gas different from a “Real’ Gas?

• Ideal gases follow all of the rules for gas behavior

• Hydrogen and Helium are the two most ideal gases that exist

• Real Gases do not always follow each of the six points of KMT.

Exceptions to the KMT

• 1. Sometimes the particles in a mixture of gases are attracted to each other because of differences between elements

• This is especially true during temperature or pressure changes

Exception #2

• As the pressure that is on a sample of a gas increases we begin to confine the gas to a smaller space

• Once trapped in a smaller space, gases will have a volume that we can measure

What set of conditions make gases most “Ideal”

• Gases are most ideal when we have:• HIGH TEMPERATURE AND LOW

PRESSURE• Under these conditions they follow

the points of KMT the best. • So……400 K and 0.1 atm is good• But…...3 K and 100 atm is NOT

GOOD• So Low Temperature and High

pressure is when they are least ideal.