Physical significance of temperature

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Heat flow into a monatomic gas at constant volume increases only translational kinetic energy, while diatomic and polyatomic gases require additional energy for rotational and vibrational modes, resulting in larger molar heat capacities. The absolute temperature reflects all types of kinetic energy, but the statement about translational energy applies specifically to monatomic gases. For diatomic molecules, the total kinetic energy is expressed as 5/2 kT, accounting for both translational and rotational energies. The principle of equipartition of energy indicates that each degree of freedom contributes to the total energy, complicating the relationship between temperature and kinetic energy in polyatomic gases. Thus, while temperature relates to all kinetic energies, the specific contributions vary between gas types.
kelvin490
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Some books say when heat flows into a monatomic gas at constant volume, all of the added
energy goes into an increase in random translational molecular kinetic energy. But when the temperature is increased by the same amount in a diatomic or polyatomic gas, additional heat is needed to supply the increased rotational and vibrational energies. Thus polyatomic gases have larger molar heat capacities
than monatomic gases.

Does the absolute temperature reflect translation kinetic energy of gases only? If all types of kinetic energy of gas particles are related to temperature, why polyatomic gases have larger molar heat capacities than monatomic gases?
 
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What confuses me, however, is that the principle of equipartition of energy says every degree of freedom contributes to 1/2 kT so total kinetic energy of diatomic molecule including rotational kinetic energy is 5/2 kT. How can we say absolute temperature relates only to translational degrees of freedom?
 
kelvin490 said:
when heat flows into a monatomic gas at constant volume, all of the added
energy goes into an increase in random translational molecular kinetic energy
Monatomic.

kelvin490 said:
total kinetic energy of diatomic molecule including rotational kinetic energy is 5/2 kT
Diatomic.
kelvin490 said:
How can we say absolute temperature relates only to translational degrees of freedom?
Because that statement is referring only to a monatomic molecule.
 
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