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Wave of phase change (MOVIE: Hot ice how-to)

  1. Jun 2, 2009 #1
    Hot ice solidifies instantaneously when its cold...
    http://www.youtube.com/v/aC-KOYQsIvU

    Are there really any oscillations or waves of different states (alternating states) in materials? Perhaps gradient of heat or a bump of pressure spreading? Sound? Electricity?
     
  2. jcsd
  3. Jun 2, 2009 #2

    Mapes

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    It looks like we're seeing the relatively fast (but not instantaneous) solidification of sodium acetate crystals from a supersaturated solution.

    Could you explain what you mean here? Crystallization is just the process of random atoms/molecules attaching to a structure with long-range order. The solid front advances as the atoms attach. The process takes some finite amount of time because the atoms must diffuse to the solid and wait to attach at the right location.
     
  4. Jun 2, 2009 #3
    I agree. It looks like ice in transparent tank with regular, milky rays spreading from the "point of impact". The front is not very regular, because it looks like a cloud, but possesses some straight edges. Then I can say that in nature waves of phase state change exist in lets say, non-equilibrium systems? or in critical state between phases? Maybe this is a mirage of demagnetizing steel magnet with a blow of hammer?

    I am writing a work on Potts model of spin and flows. If some wave can travel across a lattice and change phase (something like that), then my writing is endangered. I don't know anything. :-)
     
  5. Jun 2, 2009 #4

    Mapes

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    I wouldn't call it a wave unless you're speaking colloquially; waves have certain physical properties that these features don't, and scientists would be (justifiably) aggravated.

    Technically, it's a moving interface or boundary.
     
  6. Jun 2, 2009 #5
    Interesting point; perhaps a domino effect?
     
  7. Jun 2, 2009 #6

    Mapes

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    Sure; it's easier for an atom to attach to an existing solid phase than for a bunch of atoms to nucleate a new solid region. Supersaturation, by definition, means that nucleation isn't occurring for one reason or another.
     
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