Physical significance of temperature

  • #1
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?
 

Answers and Replies

  • #3
kelvin490
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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?
 
  • #4
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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.

total kinetic energy of diatomic molecule including rotational kinetic energy is 5/2 kT
Diatomic.
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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