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Gas that turn into liquid have a boiling point?

  1. Nov 4, 2009 #1
    I now know that gas can turn into liquid when condition are met (temperature and pressures)
    But I wonder, Is these liquid from gas have a boiling point?
    and since at normal temp (room temperature) these liquid turn back to gas state, dose that mean their boiling point are below zero?

    For liquid that boiling at temperature below than zero celcius... I'm bit confues here.


    and another, The lower pressures there are, lower boiling point of water there be right?
    than If I go into space that zero pressures, Is water will boiled instant? or turn into ice cube? is astronaut in space station have these kind of problem?

    and last, Is all gas can also turn into liquid?

    PS. English is not my native language, please forgive me if i'm wrong in gramma or spelling.
  2. jcsd
  3. Nov 4, 2009 #2
    Every compound has three major states: solid, liquid, and gas. If something exists as a gas at room temperature (about 25 degrees), that just means that the boiling point is below 25 degrees.

    Pressure has a lot to do with the phase change between liquid and gas, but not so much between liquid/gas and solid. I would suggest learning how to read phase diagrams, and looking at some samples (water is a simple one to start with). This was one of the first things I learned to do in my university general chemistry course, and it will help you understand these ideas much better.
  4. Nov 6, 2009 #3
    Well... I do look into phase diagrams like you just said, but it's not quite awnser my curious.

    To be hornest, I'm not people in science field Just a writer who want infomation for my sci-fi story, so can't say I completely understand that phase diagrams.

    First, that diagram alway show above zero temperature, so I still don't know If it gonna boiled at below zero temp.

    second and last question still on clue.


    okay, at least this.
    If temperature in room has drop down to -270 degree celcius (not absolute zero yet) are all gas in that room will turn into liquid? or more, freeze and tune into solid gas?
  5. Nov 6, 2009 #4
    Some compounds do boil at below zero. For example, diatomic nitrogen (N2), oxygen (O2), and helium exist as gases well below zero, which means their boiling points are well below zero.

    If you get that close to absolute zero (in the range of 3 degrees above it), most compounds will turn to solid state. For example, at my university, a physicist recently observed supersolid helium-4. These types of solids usually have some very interesting properties. If you are writing a sci fi story, you should definitely look into more information about "superfluids" and "supersolids."
  6. Nov 6, 2009 #5
    Thank you, most of my curious is clear. normal people think about boiled is must be HOT but it can be freeze too, surely interesting.

    and I also look into superfluid and supersolids, pretty amazing. Liquid than can creep verticaly and atom that can exchang position.


    Oh,What about water at zero pressures in room temprature (or in space)?

    and superfluid, if it really are zero viscosity, does that mean we can't not swim in it? no metter how well we can swim in normal water, it no use in superfluid right? or we can still swim it normaly.
    Last edited: Nov 6, 2009
  7. Nov 8, 2009 #6
    Water in a zero pressure environment (at room temperature, ~25C) will exist in the gas phase. Since it is at room temperature, it has a fair amount of kinetic energy, which means that the vapor pressure is greater than zero. When the vapor pressure is greater than the ambient pressure, that's when liquids begin to turn to gases. So if you had a glass of water in space, it would boil pretty quickly.

    As for superfluids, I doubt you could swim in one. The low viscosity would make it impossible to use any type of swimming motion to move your body, so you would probably just sink. Of course, this is assuming you could find a superfluid warm enough to swim in without freezing to death :)
  8. Nov 8, 2009 #7
    That's the type of awnser I like to hear.

    Thanks you, now I have better idea for my work.
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