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Mechanisms of Supercooling and Supersaturation

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  1. Sep 18, 2014 #1
    I have a couple of questions:

    The homogeneous freezing temperature of water is listed at -42C. However, from the equations formulated to find critical radius here, I did not see any factors which restricts the homogeneous nucleation temperature to a certain value. How is the homogeneous nucleation temperature defined? I can see how the probability of a nuclei of critical radius increases with decreasing temperatures. However, in the absence of heterogeneous nucleation sites, would a block of water left at say -20C never freeze, or would it eventually freeze after a very long time? Microscopically how is a solid nucleus formed?

    In the same Wikipedia article, I did not understand this statement:
    what is meant by solid and liquid pressure, and since they are different, can phase change be considered isobaric?

    How is supersaturation achieved? I think one way is to lower the temperature of some water vapour inside an enclosed container with no nucleation sites. Is it possible to generate a supersaturated system by evaporation, such that water continue to evaporate even when P > P_sat(T_system)?

    Similar to the above question, if I have liquid water in equilibrium with its vapour (P_vapour = P_sat(T)) inside an closed system with no nucleation sites at temperature T, if I lower the temperature, does the system supersaturate, or does vapour begin condensing?

    Thank you
     
  2. jcsd
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