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Water vapor at approx. 300 degrees Celsius

  1. Jul 26, 2010 #1
    Ive heard that at somewhere around 300 degrees Celsius (cant remember the exact number), you cant liquidise it anymore. Is this fact correct?

    Thanks in advance,
  2. jcsd
  3. Jul 26, 2010 #2
    You can liquidise a vapour by applying a high enough pressure but only if the vapour is at a temperature lower than its "critical temperature".If the temperature is higher than the critical temperature then applying pressure results not in a liquid but in a compressed vapour.
  4. Jul 26, 2010 #3
    Thats what I thought. Thanks !
  5. Jul 26, 2010 #4
    This shows up the difficulty with using common terms in science - a supercritical fluid is neither liquid nor gas. (And yet it's both at the same time).

    Is a liquid crystal a solid or a liquid? - Same problem.
  6. Jul 26, 2010 #5
    I'd need to check a book of steam tables but I'm pretty sure that water can still be aliquid at a lot more then 300 Deg C
  7. Jul 26, 2010 #6
    I just checked and the critical temperature of water is 374Deg C.
  8. Jul 26, 2010 #7
    Ah, yes, the critical point is 374 degrees C. (The OP did say 'about' 300)
    It's surprisingly low though.
  9. Jul 26, 2010 #8


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    I'm pretty sure what OP heard is a mention of critical point. Sounds like it. Past these 374°C, there is no phase transition from vapor to liquid, and that might come out as "can't liquidise" to someone who didn't quite get the point.
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