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Is osmosis a thermal machine?

  1. Mar 24, 2016 #1
    I have read that osmosis " works like a machine ". It lifts weight ( this is obvious ) on the expense of thermal energy.

    Does anyone has any thoughts about how it consumes thermal energy?
    Thank you in advance.
  2. jcsd
  3. Mar 24, 2016 #2


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    Staff: Mentor

    Could you give a reference for that?

    I don't see how this can be correct. Osmosis is based on a difference of chemical potential, not temperature. I wouldn't know how to qualify the kind of energy it consumes, but it is not thermal, nor chemical (in the usual sense of that word).
  4. Mar 24, 2016 #3
    Thanks for your answer. I don't remember the text where i met this expression but per example the hyperphysics article defines osmosis as a diffusion process driven by internal energy and internal energy is defined as energy associated with random motion of molecules.

    That is something like thermal energy if i understand what i read.
  5. Mar 25, 2016 #4
    Osmosis is a pressure gradient, caused by chemical potential. Think potassium and sodium.
  6. Mar 25, 2016 #5
    When you have time, could you explain what you mean?
  7. Mar 27, 2016 #6


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    Gold Member

    I don't know what you mean by "consumes thermal energy."
    But anyways, yes osmosis can be considered as being a phenomenom of thermodynamics.

    If you take the ideal gas equation, PV=nRT, and arrange it just a bit, you get,

    Replace P with π, and n/V and you get the osomotic pressure equation
    π = cRT, where c is the concentration of the solute in moles per liter.

    You can read some discussion here,
  8. Mar 27, 2016 #7
    Thank you for your answer and especially for the link
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