Relation between temperature and average translational kinetic energy.

[Nikhil Rajagopalan]

Dear Experts,
I have read from various sources that the temperature of a gas is related to the "average translational kinetic energy" of a molecule of gas. When there are molecules that support motion other than translational ,which may also have rotational and vibrational motion, How does those two modes of motion not contribute to the temperature.

 

[Dale]

When there are molecules that support motion other than translational ,which may also have rotational and vibrational motion, How does those two modes of motion not contribute to the temperature.

They do contribute to the temperature. That is in fact why the statement you first made is actually incorrect. It should be “the temperature of an ideal mono-atomic gas is related to the ‘average translational kinetic energy’ of a molecule of gas”.

Unfortunately, that important restriction is often neglected, which leads students to the mistaken conclusion that this relationship to KE is a general relationship instead of one particular to a specific kind of material. You have done well to identify the problem with that description.

 

[Nikhil Rajagopalan]

Thank you Dale. That was very helpful.