Kinetic theory

• • Molecules in a gas are in constant random motion at high speeds
• • The temperature of the gas is related to the average kinetic energy of the molecules
  • The hotter the gas, the higher the average kinetic energy
  • The cooler the gas, the lower the average kinetic energy
• • As the temperature of a gas increases, the average speed of the molecules also increases
  • Since the average kinetic energy depends on their speed, the kinetic energy of the molecules also increases if its volume remains constant
• Pressure

  • Molecules of gas in a container will collide with the container walls
  • Pressure is defined as the force exerted per unit area of the container
• The equation for pressure is

  Pressure = Force / Area
• • Therefore a gas at high pressure has more frequent collisions on the container walls and therefore overall more force per unit area
• • If the gas is heated up, the molecules will travel at a higher speed
  • This means they will collide with the walls more often
  • This creates an increase in pressure
• • Therefore, at a constant volume, an increase in temperature increases the pressure of a gas and vice versa