Question about Temperature and KE

[Benman44]

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I have notes saying that KE is the same for all things at the same temp and also some saying that no they are not the same please help!

 

[Cool Beans]

Two gases will have the same kinetic energy if they are at the same temperature. Note that this does NOT mean that they will have the same speed as the lighter one will have a higher rms speed and will effuse and diffuse faster (according to Graham's Law of Effusion).

 

[Kahr]

Two gases will have the same kinetic energy if they are at the same temperature. Note that this does NOT mean that they will have the same speed as the lighter one will have a higher rms speed and will effuse and diffuse faster (according to Graham's Law of Effusion).

👍 Very concise.

Average kinetic energy changes directly with temperature.

 

[Benman44]

thats what i thought but destroyer claiims that all molecules of an ideal gas have the same KE at a constant temp is false..... is it because its = to the average KE? not each ones KE separately?

 

[Kahr]

thats what i thought but destroyer claiims that all molecules of an ideal gas have the same KE at a constant temp is false..... is it because its = to the average KE? not each ones KE separately?

Ahh, yes, that caveat. I believe that's correct, it's the average, not that all of them are the same individually. (Will eventually cross-reference with Chad's chem videos, and re-post if something conflicts here)

 

[Jackson-Ave-Dental]

The keyword here is AVERAGE.

The formula for KEavg is:
KEavg = 3/2 KT

As you can see... the KEavg is proportional to the temperature. This only means that the average of all the molecules are the same but each individual molecule does NOT have the same KE. This is evident in boltzman's distribution.

Please take a look at that graph if you have not done so (boltzman). Also please note that the KEavg is slightly to the right of the peak on the graph; it is not equal to the peak!