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Kinetic energy and heat energy of molecule?

  1. Jul 3, 2014 #1
    I know that .
    Average kinetic energy of a molecule is (f/2)kT (for translational motion.where f=3 )

    In my textbook given that...

    If the degree of freedom of the gas molecule is f then the average heat energy of each molecule of the gas is = E(avg.) = (f/2)kT

    which is same as the average kinetic energy.

    Are the avg. kinetic energy and heat energy both are same or there is difference between them?
  2. jcsd
  3. Jul 3, 2014 #2


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    I think the textbook may just be using slightly sloppy language, using "heat energy" for what should be "kinetic energy". As heat is not a state function, there is no "heat energy" function that can be associated with an equation of state. Heat is energy flow into or out of a system that is not work.
  4. Jul 3, 2014 #3
    Thermal energy might have been a better choice of words.
  5. Jul 3, 2014 #4
    thermal Energy and kinetic energy of molecule is same?
    Last edited: Jul 3, 2014
  6. Jul 3, 2014 #5


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    It depends on the definitions. I would prefer simply the phrase "total energy" of the material. For an ideal (perfect) gas the total energy is the same as the kinetic energy of the molecules, for a non-perfect gas, there can be potential energy contributions to the total energy.

    Thermal energy is often just another word for "heat".
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