Pressure in gases

• • A gas can be compressed or expanded by pressure changes.
  • the pressure produces a net force at right angles to the wall of the gas container (or any surface).
• Increasing the volume of a gas results in a decrease in pressure because:

  • molecules become more spread out and so time between collisions increases
  • this reduces the rate of collisions
  • rate of change of momentum decreases, and so force exerted on container decreases, resulting in a lower pressure
• the product of pressure and volume (for a fixed mass of gas at a constant temperature) is constant
• Equation linking pressure volume and constant

  • pressure x volume = constant

  Pressure in pascals (Pa), volume in metres cubed