Factors that affect gas pressure

• Particles in gases


  • Free to move about in completely random directions
  • Rebound and carry on in a different direction when they hit a wall
  • Exert a force whenever they collide with the walls of the container
• Pressure


  The force being exerted per unit of area or the force divided by the area
• Factors affecting pressure


  • Number of collisions
  • Energy of each collision
• Heating up the gas

  • Transfers energy to the particles, increasing their kinetic energy
  • Particles move around faster
  • More collisions with the walls
  • Each collision involves more force
  • Pressure increases
• Increasing the concentration of particles

  • More particles to collide with the walls
  • More collisions
  • Pressure increases
• Decreasing the volume of the container


  • More particles per unit of volume, effectively higher concentration
  • Particles have less distance to travel between collisions
  • More collisions
  • Pressure increases
• Flexible containers (e.g. balloons)


  • Changes in temperature and concentration change the volume of the container rather than the pressure
  • Increase in number or force of collisions causes the container to expand rather than increasing pressure
• You don't have to worry about calculating any of this, just be aware that things are more complicated with expandable containers