Increasing the Pressure of a Gas

• Doing work on a gas increases its temperature
• What is the equation for work done?

  Work Done = Force x Distance = Force/area x (area x distance) = Pressure x Volume
• Work done = pressure x volume
• What does doing work on a gas mean?

  Compressing or expanding the gas, so changing the volume
• What does pumping more gas into the same volume mean?

  More particles are present, so more collisions occur per unit time with the walls, so pressure increases
• Energy is transferred to the particles when more gas is added into the fixed volume, so this heats the gas
• A fixed number of particles for a smaller volume:

  • Particles collide with the wall which is moving inward
  • So the particles gain momentum, as the rebound velocity is greater than the approaching velocity
  • So as the particle has a greater velocity, the pressure increases as the particles collide with the walls more frequently (time between collisions decreases)
  • And the temperature also increases, as the kinetic energy of each particle increases
• When the volume of gas in the syringe increased, the pressure on the inside walls of syringe decreased. Explain why.

  • more time between collisions of particles and the walls of the syringe
  • causing a lower average force on the walls of the syringe
  • and pressure is the total force per unit area
• The temperature of the helium balloon was increased

  The mass and volume of helium remained constant

  Explain why the pressure exerted by the helium inside the balloon would increase.

  • particles would have a higher mean kinetic energy
  • so increased number of collisions with the walls of the balloon per second
  • greater forces exerted in collisions
  • greater force exerted on same area