Ideal Gases (SL IB Chemistry)

• The kinetic theory of gases states that molecules in gases are constantly moving
• The theory makes the following assumptions:
  • The gas molecules are moving very fast and randomly
  • The molecules hardly have any volume
  • The gas molecules do not attract or repel each other (no intermolecular forces)
  • No kinetic energy is lost when the gas molecules collide with each other (elastic collisions)
  • The temperature of the gas is directly proportional to the average kinetic energy of the molecules

• Gases that follow the kinetic theory of gases are called ideal gases
• However, in reality gases do not fit this description exactly but may come very close and are called real gases
• The volume that a gas occupies depends on:
  • Its pressure
  • Its temperature

Diagram to show elastic collisions

In an elastic collision, energy is conserved and the particles colliding strike each other then move away in opposite directions whereas in an inelastic collision kinetic energy is not conserved and the particles usually strike and stick together