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Q & A: temperature dependence of gas thermal conductivity

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Most recent answer: 08/17/2013
Q:
Why Coefficient of Thermal Conductivity of a gas is inversely proportional to temperature?
- HARMISH (age 17)
RAJKOT,GUJARAT,INDIA
A:

I can't explain why, because it isn't true. The thermal conductivity is the product of the heat capacity per volume and the thermal diffusion constant. The thermal diffusion constant in a gas is roughly the typical molecule speed times the typical distance it travels before hitting another molecule. That distance grows inversely with the number density of the gas. The heat capacity per volume grows proportional to the number density of the gas. So the density doesn't matter. The typical molecule speed grows as the square root of the absolute temperature, so the thermal conductivity does the same.

Mike W.


(published on 08/17/2013)

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