chem ( sci )

• Kinetic molecular theory


  Theory that explains the behavior of gases
• Ideal gas laws are summaries of observations, such as the way pressure and volume are inversely proportional, or the way volume and temperature are directly proportional
• Ideal gas laws do not explain why these relationships are true
• Kinetic molecular theory


  • Consists of five postulates
  • From the postulates, all of the ideal gas laws can be derived
• Postulate 1


  1. Gas is made up of particles (atoms or molecules)

  2. Particles are always in motion

  3. Particles travel in straight lines unless they collide

  4. Particles will bounce off and change direction when they collide
• Postulate 2


  Gas is mostly empty space, the fraction of volume occupied by particles is close to zero
• Postulate 3


  Pressure is the gas particles imparting kinetic energy onto the container walls during collisions
• Postulate 4


  Gas particles do not exert gravitational or electromagnetic influence on each other, collisions are purely elastic
• Postulate 5


  Average kinetic energy of particles is proportional to temperature in Kelvin
• Keeping temperature constant


  Increasing volume decreases pressure, decreasing volume increases pressure
• Increasing temperature

  To keep pressure constant, volume must expand
• Increasing temperature while keeping volume constant

  Pressure must increase
• All ideal gas laws can be derived from the five postulates of kinetic molecular theory
• Fast moving particles