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B Condensaion / clouds

  1. Jul 27, 2017 #1
    I understand that condensation occurs when water (in gas form) looses energy and becomes liquid. What I don't understand why some surface is needed to form a liquid water
     
  2. jcsd
  3. Jul 27, 2017 #2
    Here is a wiki article on the phenomenon:
    https://en.wikipedia.org/wiki/Cloud_condensation_nuclei
    Water can condense without a surface - but the water must be chilled well below freezing before that will happen.

    I am not sure if the exact mechanism for this is described, but I would point out that without a surface, most water particles that collide with each other will be at a temperature above the ambient - simply because of the speed of the collision. Then, both the heat of the collision and the latent heat of condensation would need to be somehow surrendered to the environment.
     
  4. Jul 27, 2017 #3

    sophiecentaur

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    What happens at the spout of a boiling kettle?
     
  5. Jul 27, 2017 #4
  6. Jul 27, 2017 #5

    anorlunda

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    Leave it to an Englishman to focus on a boiling kettle. :wink: I love those powerful electric tea kettles you have there.
     
  7. Jul 27, 2017 #6

    sophiecentaur

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    The water needs to nearly boiling when it first comes into contact with the tea. Everywhere else in the World they pour luke warm water - or even dip the tea bag into a cup of water that was heated way back at the bar or in the kitchen. You've no idea, you guys. But you put whisky into ice, too!!!!!:smile:

    I scanned through it but couldn't actually find that statement and I also looked at the other article. We all know that you can form fog and mist without the temperature being very low so they must be looking deeper and considering large droplet formation. It'll be the temperature that determines whether large enough drops can form to cause rain, probably because there will be an equilibrium when the evaporation rate is the same as the condensation rate.
     
  8. Jul 27, 2017 #7
  9. Jul 27, 2017 #8
    From the first paragraph of the wiki article:
    At low altitudes and certainly indoors at a residence, there are always lots of airborne particles.
    The second article I cited (the college Meteorology text) also notes that very humid conditions are unusual in polluted urban areas - because there are so many seeds available in the air.
     
  10. Jul 27, 2017 #9

    davenn

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    it doesn't say must be super cooled

    "can be cooled ..... before" big difference


    this is all related to dew point
    https://en.wikipedia.org/wiki/Dew_point
     
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