Temperature & Pressure | Physics for GCSE/IGCSE - Year 11 PDF Download

Motion of Particles in a Gas

• Molecules within a gas exhibit continual, erratic movement at elevated velocities.
• This random motion entails molecules traversing without a defined trajectory and experiencing abrupt alterations in their motion upon collision:
  • With the walls of the container.
  • With other molecules.
• The pressure exerted by a gas results from collisions with the surface (walls) of the container.

Pressure & Force of Particles in a Gas

• Gases naturally fill their containers.
• Pressure is the force per unit area.

• As gas particles move randomly, they encounter the walls of their containers, resulting in collisions.
• These collisions generate a net force perpendicular to the container's wall (or any surface).
• Consequently, a gas under high pressure experiences more frequent collisions with the container walls and exerts a greater force.
  • Thus, elevated pressure correlates with increased force exerted per unit area.

• You can feel this force by sealing your mouth and inflating your cheeks.
• The pressure on the cheeks results from the gas particles exerting force perpendicular to them.