Can Heat Flow from Cold to Hot?

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SUMMARY

This discussion centers on the concept of heat flow, specifically whether it can occur from a colder atom to a hotter atom. It establishes that while energy transfer can happen during oblique collisions between atoms of the same mass, this does not constitute a true flow of heat. A net transfer of energy among multiple molecules is required for heat flow to be classified as such. The distinction between energy transfer and momentum transfer is emphasized as crucial in understanding this phenomenon.

PREREQUISITES
  • Understanding of thermodynamics principles
  • Familiarity with kinetic energy concepts
  • Knowledge of atomic and molecular behavior
  • Basic grasp of momentum and energy transfer
NEXT STEPS
  • Research the laws of thermodynamics, particularly the second law
  • Explore kinetic theory of gases and its implications on heat transfer
  • Study the concept of energy transfer in molecular collisions
  • Investigate the role of temperature gradients in heat flow
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Students of physics, researchers in thermodynamics, and anyone interested in the principles of heat transfer and molecular interactions.

NicholasB54
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If heat flow is the momentum change from a faster moving atom or molecule to a slower moving one, and momentum is mass x velocity is it possible - for a very limited amount - for heat to flow from a slower (colder) heavy atom to a faster moving (hotter) atom ?
 
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(1) It's energy transfer, not momentum transfer, that's relevant.

(2) It is, I believe, possible in an oblique collision for a faster molecule to pick up speed (and hence KE) from a slower molecule of the same mass.

(3) But we wouldn't classify this as a flow of heat. To constitute a flow of heat we'd need a net transfer of energy for many molecules.
 
I was confusing energy change and momentum change alright

Thanks Philip
 

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