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    Temperature dependence of heat capacity of diatomic gas

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    Describe the temperature dependence of the heat capacity of a diatomic gas.

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    You should just draw the sketches qualitatively, don't do any complicated computations here.

    At zero temperature the heat capacity is zero. All the degrees of freedom are "frozen", i.e. k T is smaller than the spacing of the energy levels. Then, if we raise the temperature, the heat capacity of the translational degrees of freedom rises to it's asymptotic value of 3/2 k. Depending on the volume this transition from zero to 3/2 k happens over the course of
    10^(-10) K. So, this would be the first part of the sketch.

    Next the rotational degrees of freedom start to kick in. This happens at a few tens of K, you can take e.g. 40 K. So, what you see is that the value of the heat capacity slowly starts to rise from 3/2 k to 5/2 k around 40 K ...

    Solution Summary

    A detailed explanation is given. The expert examines temperature dependence of heat capacity of diatomic gas.