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Is water 'supposed' to boil at a lower temperature?

  1. Jul 4, 2013 #1
    A biology teacher once said to his class something to the effect of water posessing qualities that it should not. I don't remember what reasons he gave but my notes say that water 'should' exist as a gas at -90 degrees Celsius at 1 bar.

    Do any of you know why this is?
  2. jcsd
  3. Jul 4, 2013 #2
    I assume what he meant was that if you model water without taking into hydrogen bonding it has much weaker inter-molecular forces?
  4. Jul 4, 2013 #3
    Does that mean a single atom of water evaporates at a lower temperature than 100 degrees Celsius?
  5. Jul 4, 2013 #4


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    a single molecule of water can't form liquid or solid
  6. Jul 4, 2013 #5
    Water can evaporate at temperatures below 100C if its partial pressure in the gas phase in less than 1 atm. Just set out a small bowl of water in your kitchen for a few days and see what happens. Water will always evaporate if its partial pressure in the gas phase is less than the equilibrium vapor pressure at the liquid temperature.

  7. Jul 4, 2013 #6
    Ok, from what I've read from you guys, water exists as a liquid at a pressure of 1 atm at temperatures of 0 degrees Celsius and 100 degrees Celsius because of hydrogen bonding. That means the individual hydrogen atoms in each H20 are attracted to the oxygen atom of other water molecules, right?
  8. Jul 10, 2013 #7
    What he means is that, if you compare water to other molecules of a similar size (ammonia, hydrogen chloride, methane) it has unusually high melting, boiling points and specific heat capacities due to the hydrogen bonding in water.
  9. Jul 11, 2013 #8
    Boiling occurs when the vapour pressure equals the atmospheric pressure. Vapour then forms throughout the body of the liquid. Evaporation occurs from the surface of the liquid at all temperatures.
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