AP Chemistry Unit 3.5 The Kinetic Molecular Theory of Gases

Theory of Gases

1. Gases consist of particles (atoms or molecules) that are in constant random motions
2. Gas particles are constantly colliding with each other and the walls of their container
3. There are no interactive forces (attraction or repulsion) between the particles of a gas

• • Collisions between gasses is elastic: no effect and KE is conserved
    • For real gasses: between collisions, particles have constant velocity and direction which change after collisions

4. The avg kinetic energy of gas particles only depends on the absolute temperature of the gas → all gases at the same temperature have the same avg kinetic energy

• • But the speed of the particles is affected by both temperature and the molar mass of the gas
    
    • Smaller particles travel at faster speeds than heavier/larger gases.

 Maxwell-Boltzmann Practice

• A Maxwell-Boltzmann distribution show the relationship between temperature and average KE
• 

• Heavier gasses will have graph like the lower temp one
  
  • Lower temp → peak more to the left, higher, extends below AE

Characteristics of an Ideal Gas:

• Ideal gases have negligible volume, pressure, and forces
• The pressure exerted by an ideal gas is not affected by the identity (composition) of the gas particles

Real Gas Behavior

• Real gases have volume, pressure, and InterMF
• Their particles are all able to condense and vary in size