Ideal Gases (DP IB Chemistry): Revision Note

Ideal gases

Kinetic theory of gases

• The kinetic theory describes the behaviour of gas particles and assumes:

  • Gas molecules are in constant, rapid, random motion

  • The volume of individual gas molecules is negligible compared to the total volume of the gas

  • No intermolecular forces exist between gas particles, they do not attract or repel one another

  • All collisions between gas molecules are perfectly elastic (no kinetic energy is lost)

  • The temperature of a gas is directly proportional to the average kinetic energy of its particles

Ideal vs. real gases

• Gases that follow all assumptions of the kinetic theory are called ideal gases

• Real gases do not perfectly follow this model, but under low pressure and high temperature, they behave similarly to ideal gases

Factors affecting gas volume

• The volume that a gas occupies depends on:

  • Pressure (P)

  • Temperature (T)

Diagram to show elastic collisions