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

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Discussion Overview

The discussion revolves around the phenomenon of phase change in materials, specifically focusing on the solidification of sodium acetate and the potential existence of oscillations or waves during this process. Participants explore theoretical implications, crystallization dynamics, and the nature of phase transitions in non-equilibrium systems.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that the solidification of sodium acetate crystals occurs relatively quickly, but not instantaneously, and involves a process of atoms/molecules attaching to a structured solid.
  • There is a suggestion that oscillations or waves of different states might exist in materials, potentially linked to gradients of heat or pressure, sound, or electricity.
  • One participant questions whether the observed solid front during crystallization could be considered a wave, arguing that it is more accurately described as a moving interface or boundary.
  • Another participant mentions the possibility of phase state changes occurring in non-equilibrium systems and raises the idea of a "domino effect" in the context of crystallization.
  • Concerns are expressed about the implications of these discussions on theoretical models, such as the Potts model of spin and flows, particularly if waves can travel across a lattice and induce phase changes.

Areas of Agreement / Disagreement

Participants express differing views on whether the phenomena observed can be classified as waves, with some arguing for a colloquial interpretation while others emphasize the technical distinctions. The discussion remains unresolved regarding the existence of oscillations or waves during phase changes.

Contextual Notes

Participants note that crystallization involves finite time processes due to atomic diffusion and attachment, and there is an acknowledgment of the complexities involved in defining phase transitions in non-equilibrium systems.

giann_tee
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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?
 
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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.

giann_tee said:
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?

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

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 let's 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. :-)
 
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.
 
Mapes said:
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 (rightly) aggravated.
Technically, it's a moving interface or boundary.

Interesting point; perhaps a domino effect?
 
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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