Gas Pressure (Cambridge (CIE) AS Chemistry): Revision Note

Gas Pressure

• Gases in a container exert a pressure as the gas molecules are constantly colliding with the wall of the container

Illustration of gas pressure

Changing gas volume

• Decreasing the volume (at constant temperature) of the container causes the molecules to be squashed together which results in more frequent collisions with the container wall

• The pressure of the gas increases

• The volume is therefore inversely proportional to the pressure (at constant temperature)

  • A graph of the volume of gas plotted against 1/pressure gives a straight line

How decreasing the volume of a gas affects collision frequency 

Changing gas temperature

• Increasing the temperature (at constant volume) of the gas causes the molecules to gain more kinetic energy

• This means that the particles will move faster and collide with the container walls more frequently

• The pressure of the gas increases

• The temperature is therefore directly proportional to the pressure (at constant volume)

  • A graph of the temperature of gas plotted against pressure gives a straight line

How increasing the temperature of a gas affects collision frequency