GCSE Physics (AQA)

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Work on a Gas

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Particle model of matter Particle model and pressure

Work on a Gas

3:56 Gas Pressure and Kinetic Theory
Spec 4.3.3.3
Previous Calculating Gas Volume & Pressure Next The Nucleus
  • The pressure of a gas exerts an outward force against its container.
  • Gas consists of particles moving randomly at high speed, spreading out in a container.
  • Particles collide with the container walls, creating outward force or pressure.
  • To compress a gas, work must be done against this force.
  • Work involves forces causing a change in energy, either by moving an object or opposing a force.
  • Compressing gas involves moving a press downwards against gas pressure.
  • Doing work against gas pressure transfers energy to the gas's internal energy.
  • Compressing gas increases particle speed, akin to a ball hit by a tennis racket.
  • Increased particle speed raises kinetic energy and internal energy of the gas.
  • Gas temperature is a measure of kinetic energy; increased kinetic energy raises temperature.
  • Exams require explaining changes in internal energy and temperature due to work done and container wall movement.
  • A common scenario: pumping a bicycle tire with a pump, where the pump end becomes hot.
  • Pumping quickly does work against air pressure, heating the pump end.
  • Work transfers energy to air's internal energy, increasing molecule speed and temperature.
  • Pumping slowly may not show noticeable temperature change, allowing the pump to cool down.

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