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Kinetic Molecular Theory

The Kinetic Molecular Theory

Table of Contents

Terms and Formulae

While the ideal gas law deals with macroscopic quantities of gas, the kinetic molecular theory shows how individual gas particles interact with one another. The kinetic molecular theory contains a number of statements compatible with the assumptions of the ideal gas law. It is worthwhile to list them here:

  • Molecules are point masses (they have no volume)
  • Gas molecules exert no force on each other unless they collide
  • Collisions of molecules with each other or the walls of the container do not decrease the energy of the system
  • The molecules of a gas are in constant and random motion
  • The temperature of a gas depends on its average kinetic energy avg(1/2mv 2) = 3/2kT . In other words, the energy of an ideal gas is entirely kinetic.

The amazing thing about the kinetic molecular theory is that it can be used to derive the ideal gas law. Such a derivation links the microscopic claims of the kinetic molecular theory to the very visibly macroscopic behavior of the ideal gas law. The derivation is beyond the scope of this note, but you should ask your instructor to show you if you're interested.