Kinetic Kinetic Molecular Molecular Theory & Theory & Gas LawsGas Laws

It’s all about the particlesIt’s all about the particles

•The molecules are in constant motion. This motion is different for the 3 states of matter.

              

Solid - Molecules are held close to each other by their attractions of charge. They will bend and/or vibrate, but will stay in close proximity.

•                             Liquid - Molecules will flow or glide over one another, but stay toward the bottom of the container. Motion is a bit more random than that of a solid.               

• Gas - Molecules are in continual straightline motion. The kinetic energy of the molecule exceeds the attractive force between them. They are far apart and move freely of each other.

• When the molecules collide with each other, or with the walls of a container, there is no loss of energy.

PressurePressure• The pressure of a gas is caused

by collisions of the molecules with the walls of the container.

Pressure (continued)Pressure (continued)• The magnitude of the pressure is

related to how hard and how often the molecules strike the wall

Pressure (continued)Pressure (continued)• The "hardness" of the impact of

the molecules with the wall will be related to the velocity of the molecules times the mass of the molecules

PressurePressure

Absolute TemperatureAbsolute Temperature• The absolute temperature (kelvin)

is a measure of the average kinetic energy of its molecules

• If two different gases are at the same temperature, their molecules have the same average kinetic energy

• If the temperature of a gas is doubled, the average kinetic energy of its molecules is doubled

Average Kinetic EnergyAverage Kinetic Energy

What is…..What is…..

•The effect of a volume increase at a constant temperature ?

Answer:Answer:• Constant temperature means that

the average kinetic energy of the gas molecules remains constant

• This means that the speed of the molecules remains unchanged

• If the speed remains unchanged, but the volume increases, this means that there will be fewer collisions with the container walls over a given time.

What isWhat is……

•The effect of a temperature increase at constant volume?

Answer:Answer:• An increase in temperature means an

increase in the average kinetic energy of the gas molecules.

• There will be more collisions per unit time, furthermore, the momentum (strength) of each collision increases (molecules strike the wall harder)

• Therefore, there will be an increase in pressure