• For a fixed mass of a gas held at a constant temperature:

pV?= constant

• Where:
  • p?= pressure in pascals (Pa)
  • V?= volume in metres cubed (m³)

   

• This means that the pressure and volume are inversely proportional to each other
  • When the volume?decreases?(compression), the pressure?increases
  • When the volume?increases?(expansion), the pressure?decreases

   

• This is because when the volume decreases, the same number of particles collide with the walls of a container but?more frequently?as there is?less space
  • However, the particles still collide with the same amount of?force?meaning greater force per unit area (pressure)

   

• The key assumption is that the?temperature?and the?mass?(and number) of the particles remains the same

Increasing the volume of a gas decreases its pressure

• This equation can also be rewritten for comparing the pressure and volume before and after a change in a gas:

P₁V₁?=?P₂V₂

• Where:
  • P_1?= initial pressure in pascals (Pa)
  • V_1?= initial volume in metres cubed (m³)
  • P_2?= final pressure in pascals (Pa)
  • V_2?= final volume in metres cubed (m³)

   

• This equation is sometimes referred to as?Boyle's Law

Initial pressure and volume, P₁?and V₁, and final pressure and volume, P₂?and V₂