Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Temperature & molecule speed

  1. Jul 12, 2008 #1
    Can someone explain if my understanding is correct- that temperature of say a liquid is proportional to the speed of the molecules?

    My idea is if there was a way to sort different molecules by speed, could you say in theory, take 1litre of water at 30degrees and pick out the fastest molecules and say have 50mls of water at 50degrees C leaving the remainder 950mls at 28 degrees centigrate etc???
  2. jcsd
  3. Jul 12, 2008 #2
  4. Jul 13, 2008 #3
    Excuse me ??? No one asked to contribute to my question, so that sort of attidude not required thanks. The post you reference does not answer the point about 'sorting out' the fasted moving molecules.

    My question is if there was some way to sort molecules could you get some hotter water out of some colder water - in theory
  5. Jul 13, 2008 #4
    why the hell are you going off at me for? remember this question:
    that link I gave you answered that question. Not to mention, all I said was search your questions before asking - it's a sticky thread if you havn't noticed.

    to your molecule question: If there was a way to sort out molecules; the question would then be how do you separate the hotter molecules from the colder ones?

    rough estimates or exactly?
  6. Jul 13, 2008 #5


    User Avatar
    Gold Member

    It's a tricky question, with an answer that is more subtle than one might think. The short answer is: no, it won't work. As to why, you'll have to do some more reading, as this the answer is more involved than a forum will really allow.

    Read up on Maxwell's Demon - it deals directly and exactly with what you are asking.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook