Pressure of Gases

• Doing work on a gas


  1. Involves a transfer of energy

  2. Increases its internal energy

  3. Can also cause an increase in the temperature
• Compressing a gas


  1. A force is used to push a piston by a certain distance

  2. Decreases the volume of the gas

  3. The molecules move around faster and therefore have a higher kinetic energy

  4. This increase in kinetic energy increases its temperature
• Gas allowed to expand


  1. The gas will do work instead

  2. Causes the gas to lose energy

  3. Results in a decrease in temperature
• Doing Work on a Gas (HT only)


  • Bicycle pump
  • Diesel-powered vehicle engines
  • Pressurised carbon dioxide released from a high-pressure cylinder