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Thread: Super-cooled Liquid

  1. #1 Super-cooled Liquid 
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    Are super-cooled liquids fact or fiction. I heard from a teacher years ago that old glass is rippled and thicker at the bottom bc it slowly flows downward then I heard that was false on some myth-buster type programme. Which is true?


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  3. #2  
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    yeah its as far aa i know jst one of these urban legends that doesnt seem to go away. glass is definately a solid due to way it reacts to force at normal tempretures its molecular composition is rigid and doesnt flow either


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    On wikipedia it describes a supercooled liquid as a liquid cooled below it's freezing point without becoming solid which has nothing to do with glass or wax or any of those things that I was falsely told to be the mysterious "fifth state of matter". sounds like witchcraft to me.
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  5. #4  
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    Yes, supercooled liquids exist and glass is an example of a supercooled liquid.

    But the old story about glass being thicker on the bottom because it flows is a myth. A super-cooled liquid is still a solid. It's just a solid without any ordering in its atoms.
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  6. #5  
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    Yep I agree with Scifor, glass is reckoned to be a supercooled liquid, when you heat it, it just softens more as the temperature rises. Compare that with lead for example which just seems almost to 'burst' into a lquid as it is heated. Iron softens as heated yet it too has a melting point where it turns to liquid.
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    Why do I know glass as an amorphous(sp?) solid then? I don't think that glass is a super cooled liquid because there is a second order phase transition as it cools. Also, in glass while the molecules are not in a rigid lattice structure, but they are rigidly bound unlike in fluids where the molecules are not rigidly bound. Supercooled liquids have no structure by definition.

    I've read that thicker glass at the bottom is a result of the glass making process that was used in antiquity, before float glass.
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  8. #7  
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    glass isn't a supercooled liquid. A supercooled liquid is what zythum said, and glass is what Keith said. And yes, supercooled liquids exist, but only for short periods of time: something doesn't stay supercooled. On a cooling curve, it would be that little point that's below the final, constant temperature.

    Edit: HERE is a good wikipedia article on supercooling.
    Whence comes this logic: no evidence = false?

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  9. #8  
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    The conclusion of this article is probably closer to the truth ie it appears the jury is still out pending a greater understanding of the molecular structure. So I 'll change from "supercooled" to I don't know!

    http://math.ucr.edu/home/baez/physic...ass/glass.html
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    Quote Originally Posted by Megabrain
    The conclusion of this article is probably closer to the truth ie it appears the jury is still out pending a greater understanding of the molecular structure. So I 'll change from "supercooled" to I don't know!

    http://math.ucr.edu/home/baez/physic...ass/glass.html
    Oh yea, I forgot about that debate...we were talkin' 'bout it in my Chemistry class. I'd like to change my opinion too...I don't know
    (my definition of a supercooled liquid still sticks, though :wink: )
    Whence comes this logic: no evidence = false?

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  11. #10  
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    There is also super hot liquids.
    or something.

    When a liguid heats above is boiling point with no nucleation points within the liquid then it doesnt boil but rather explodes..

    Trust me that i know this

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  12. #11  
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    I suppose you could cool say water to a couple of degrees below freeazing point by cooling it and simultanously moving the liquid around ?
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  13. #12  
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    Sheeeesh! Still that oooooooooooold story (legend) that glass in the old church windows is flowing

    That supercooled liquid was just meant to be a crutch to describe to the non-materials-scientist what the structure resembles. Just like the analogies in th estring theory or similar. This analogy dates back in time to the 1910s and 1920ies when the structural anlysis with x-rays came up and nobody quite understood the structure of amorphous solids.

    And the most common definition nowadays is that the distribution function in glasses is non-periodical or that the physical properties (not only the TCE but also electrical conductivity, optical density etc.) change steady but not homogeniously during heating.




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  14. #13 Re: Super-cooled Liquid 
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    Quote Originally Posted by zythum
    Are super-cooled liquids fact or fiction. I heard from a teacher years ago that old glass is rippled and thicker at the bottom bc it slowly flows downward then I heard that was false on some myth-buster type programme. Which is true?
    Maybe you can be interested in the famous "Pitch Drop Experiment":
    http://www.physics.uq.edu.au/pitchdrop/pitchdrop.shtml

    I don't know if glass has a similar behaviour.
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  15. #14 Re: Super-cooled Liquid 
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    Quote Originally Posted by blue star
    Maybe you can be interested in the famous "Pitch Drop Experiment":
    http://www.physics.uq.edu.au/pitchdrop/pitchdrop.shtml

    I don't know if glass has a similar behaviour.
    NO, for all practical and theoretical purposes - @ room temperature glass is a SOLID no supercooled liquid, it is under no circumstances behaving remotely like a liquid - newtonian or non-newtonian - at these temperatures.
    That's also the reason why the temperature-viscosity-diagrams for glass end at some point below the annealing temperature i.e. below a viscosity of 1014.5 Poise. It does not make sense to continue the graph to room temperature. At the working temperature where the viscosity is 104 Poise glass has the viscosity of honey and for ordinary SLS-glass this happens at a temperature of arounnd 900° C, annealing is at around 500° C. If you imagine the viscosity curve beeing continued down to room temperature, the viscosity would probably be around 1030 Poise. For a body to show visible deformation under it's own weight at this viscosity the age of the universe would not suffice, let alone the time passed from medival times until today.

    NO LIQUID @ 20°C - NEVERRRRRRR

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  16. #15 Re: Super-cooled Liquid 
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    Quote Originally Posted by Twaaannnggg
    P.S. Why the heck does the [sup]-code for this BB not work??!! AAARGGGHH
    do you mean superscript? I believe it works just <sup>fine</sup>.
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  17. #16  
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    Let's try this here123 and here321


    Nope

    Please ChemBoy, what's the trick??
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