Gas Pressure (CIE AS Chemistry)

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

Illustration of gas pressure

Gas particles exert a pressure by constantly colliding with the walls of the container

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 

Decreasing the volume of a gas causes an increased collision frequency of the gas particles with the container wall (a); volume is inversely proportional to the pressure (b)

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

Increasing the temperature of a gas causes an increased collision frequency of the gas particles with the container wall (a); temperature is directly proportional to the pressure (b)