Talk:Supercooling

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[edit] Supercooling and glass transition

There was an incorrect information about the possibility of supercooling dow to the glass transition. Liquid water, for example, cannot be supercooled down to its glass transition, but only down to its crystal homogeneous nucleation temperature at ~150 K at atmosferic pressure. By fast cooling it is possible to avoid the crystall nucleation, going directly to the glass phase below ~136 K. I also added a reference (Debenedetti and Stanley) with all these informations. (Giancarlo Franzese, http://www.ffn.ub.es/gfranzese/) 16 Oct 2005.

[edit] Amorphous?

will is so cool thatI doubt whether supercooled compounds solidify into amorphous solids in general. Water in any case will always freeze to the Ih phase under atmospheric pressure, though the crystals will be quite small after such a rapid freezing process. -- Hankwang 19:48, 20 Mar 2004 (UTC)

The general statement is that aliquid will either crystallize or solidify into an amorphous solid. As an example [ortoterphenyl] (popular among experimental glass physicists) will often crystallize spontaneously at very low temperature (AC

[edit] Which liquids can be supercooled

It is correct that many liquids cannot be supercooled... Well in principle you can call this an experimental problem or a problem of choosing the right time scale and examining a small system, but in many cases the [metastable] supercooled state is just not meaningful, because it does not last very long. (AC)

[edit] Supercooled Water

In the temperature interval from -39 C to -120 C water freezes almost instantaneously. However in the temperature interval between -120C and -138C it is possible to have a stable supercooled phase. Below -138C the water becomes solid again. Many researchers believe that this is a glass transition. I have heard people claim that recent neutron scattering experiments suggest that there is a real phase transition at -138C (rather than a glass transition), but I know too little about that. (AC)

www.digibio.com/archive/RedHerring_com-Why_water_is_weird.htm

[edit] Dynamic arrest -> glass transition

I think that it is better to use the word [glass transition] instead of dynamic arrest

[edit] Glass is supercooled

The article contains an inaccuracy: If you chill a supercooled liquid below the glass transition temperature, then it becomes a disordered solid, but it is still supercooled. Therefore it would be better to write

"Supercooling is the process of chilling a liquid below its freezing point, without crystalization."

[edit] Contradiction?

From the article:

Its glass transition temperature is much colder and harder to determine, but studies estimate it at about 165 K (−108°C).[2] Glassy water can be heated up to approximately 150 K (−123°C).

How can glassy water only be heated up to 150 K if it can form at the higher temperature of 165 K?--kenb215 01:26, 9 December 2005 (UTC)

[edit] The application

Despite the reference, the application listed in the article is an example of exothermic crystalization from supersaturated solution, not supercooling. Supercooling is defined as cooling a fluid below its freezing point. This example is cooling a liquid below the crystalization point of a solute, not below the solution's freezing point.

The reference is filled with inaccurate uses of terminology. The reference confuses being liquid with being in solution. The heat of crystalization of NaAc is what causes the jump in temperature. Given a crystalization seed, the solution in the heat bags would begin to crystalize at 130F (it doesn't freeze at 130).Dusty78 20:18, 1 October 2006 (UTC)

This article isn't clear to a reader not au fait with super cooling. A bit of fleshing out may make it a bit more approachable.

[edit] One application of supercooling

http://www.youtube.com/watch?v=SfkHS_58yvs

"Hulk looks at beer... Hulk thinks really cool... Hulk wants beer NOW!"

This could be a very nice wedding prank. lol --Wxyrty 23:05, 19 March 2007 (UTC)

Anybody know how they chill it to get it to solidify like that? (It also looks like sodium acetate coming out of a supersaturated state.) Arc88 21:58, 15 April 2007 (UTC)

[edit] If cooled at a rate of the order of 1 million kelvins per second

This is really fast - I expect the article meant to say "milli-kelvin", but i'm not sure so I didnt change it. —The preceding unsigned comment was added by 24.68.227.168 (talk) 07:36, 22 April 2007 (UTC).

THIS IS FAKE

unless prooven i do not believe because most supercool experiments i have viewed look like they have has sodium asitate dissolved into the water... attempt to proove me wrong —The preceding unsigned comment was added by 84.66.129.246 (talk) 22:51, August 21, 2007 (UTC)

[edit] Melting point or freezing point ?

The first line says "Supercooling is the process of chilling a liquid below its melting point..." but the next line says "A liquid below its freezing point will crystallize ...". IMHO for a liquid, the 'freezing point' is applicable. If there are no objections, I'll change the 'melting point' to 'freezing point' -- WikiCheng | Talk 04:47, 27 August 2007 (UTC)

I changed it as the article melting_point clearly mentions "When considered as the temperature of the reverse change from liquid to solid, it is referred to as the freezing point." -- WikiCheng | Talk 04:53, 27 August 2007 (UTC)

i want some 1 to tell me how to do this all i know is that its kool —Preceding unsigned comment added by 75.108.40.89 (talk) 22:20, 13 November 2007 (UTC)

[edit] Superheating citation

Why is a citation needed in the part about superheating (under "Description" at the end) when there is a link to another adequately cited Wikipedia page describing the phenomenon itself? Or is the missing citation referring to another part of the paragraph? --The Sphinx (talk) 21:34, 6 January 2008 (UTC)

[edit] "Can be supercooled"

There is an unclarity both in this article and in Water about the definition of freezing point for water, and also a misunderstanding regarding melting/freezing point.

  1. What IS the freezing point for water? what are the 'certain conditions' in which water can supercool, besides the lack of nucleation points? Aren't these conditions more accurate for defining that the freezing point of water is indeed minus 42 degrees celcius?
  2. As we can see in water, the freezing point isn't always the melting point. In Wikipedia, Freezing point refers to Melting point which seems incorrect.

I'm not a chemistry guy and want to know whether these can be corrected in Wikipedia. Gil_mo (talk) 18:14, 4 February 2008 (UTC)

Melting and freezing point are statistically defined. That is, they refer to the phase transition between most probable macrostates in a thermodynamically random sample. Mathematically, they occur at the same temperature due to thermodynamic laws. If you control the randomness (by cooling really fast), you can achieve less-likely macrostates, and I believe supercooling is an example of this phenomenon. SamuelRiv (talk) 17:54, 6 February 2008 (UTC)
Mmm. I dunno. We got taught that although melting point is well defined, because of the above couple of points, "freezing point" is in fact not well defined, period. Gzuckier (talk) 19:38, 6 February 2008 (UTC)