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Glass as a thick liquid, and its relation to Thermodynamics

  1. Feb 15, 2004 #1
    well, im sure most of the readers of this forum would agree with me that glass in not a liquid. for the ones who don't ->

    solids used to be defined as highly organized crystals.

    since glass is not a highly organized crystal it has been refered to being a supercooled liquid that is still melting...

    nowadays there are amorphous solids, where the molecules of these solids are not highly organized, but are fixed in place like any crystalline solid, but in a more or less random arrangement...

    that is the case with glass, its structure does not exhibit long-range order.

    what im sayin is, why is anything refered to as having an 'original' solid or liquid state anyways?

    since all solid matter will eventually spread out into gas when its heat energy is high, and vise versa when its heat energy is low(becoming a solid), why isnt this just looked at as a linear scale that doesnt define anything as a solid, or as a liquid, or as a gas...?

    it doesnt make sense to me that things are referred to as liquid or solid... after all, isnt it based on the heat energy it contains at the time? it is all just matter, and they are in the state they are in because of our bioatmosphere, based on the relationship they have with heat energy...

    in some east ass corner of the universe what we know as iron could be some liquidy blob because of the high concentration of heat energy in that area....

    i guess it makes sense to some extent seeing as the earths temperature is seen to be in a state of balance and equilibrium compared to the masses of chaos that linger in our universe...

    but it seems to me, if we are ever going to understand the universe better, alot of the specific behaviours we see in things must be analyzed to find similarities and relationships-> such as nothing having a set liquid or solid state, because this is directly in contract to the amount of heat energy it contains...

    so defining it as a solid because of the state it takes because of the temperature of our plant in my opinion isn't efficient...

    take it easy on me guys, try not to make a fool outta me ;)

    a quick question before i am proven wrong:

    can all gases reach a heat energy level so low that it becomes liquid, and then solid? and if there are some that cannot, do these gase molecules just cease to vibrate? and wouldnt the ceasing of the vibration in itself be considered a valid phase change from gas to solid? am i missing something? -_-;;

    and i think that it is near impossible to completely stop the vibration of a molecule, but i am unsure and dont remember right now.

    btw, i would like some feedback from intelectuals on my script work with flash.

    if anyones interested-> http://huseyin.kicks-ass.net/htdocs/
  2. jcsd
  3. Feb 15, 2004 #2
    You ask many questions...

    But for a start - Why do we refer to things as Solids or liquids? Well, we live in a world where for most Humans a comfortable temp is 15-20C. We interact with the world and so refer to things as they are in 'everday' life. We also have Standard Temp and Pressure values in data books, to enable calculations to be carried out. Makes sense really. Everyone knows that water can boil or freeze, but for most of us, is always a liquid.

    Glass is a solid at room temp. Why? Because it retains its shape over a long period of time - so it is a solid. Despite what some sources claim, there is no evidence at all of it flowing at room temp. So it is a solid - the structure is irrelevant.

    As for your final question, I believe that Liquid Helium is a liquid, not a solid at the lowest temps at which it has been examined. What it may or may not be at 'absolute zero' is an invalid question as this temp can never be achieved.

    Does this help?
  4. Feb 15, 2004 #3
    What phase a substance is depends not just on the temperature, but pressure. For example, the pressure of the blade of an ice skater on the ice causes the ice to melt. The phase with the lowest Gibb's free energy will be the stable phase (although in some instances it might take eons to reach the stable phase).

    A phase change is a discontinuous change, so it is possible to define a solid, liquid, or gas (except past the critical point where one cannot differentiate between a liquid and gas).

    Liquid helium cannot be solidified at absolute zero except at very high pressures (once again showing why it's not just temperature but also pressure).
  5. Feb 15, 2004 #4
    With respect to the person that said glass doesn't flow at room temperature I must disagree. Glass does indeed flow but veeeeerrrrryyy slowly. If you examine windows in old houses built in the 1700's that have an original glass window pane or two you will notice that the bottom of the pane is always thicker than the top. We try to define and catagorize things from our point of view so that at room temperature for all intent glass is a solid because the material of course doesn't take the shape of any container. ( usually we are using glass as a container) Some have classified glass as an amophorus solid .
  6. Feb 15, 2004 #5


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    Sorry, but please do some research before commenting. What you have said is false, and Adrian is correct. Glass does not flow at room temperature. The reason the windowpanes in old houses are thicker near the bottom is because they were made poorly in the first place, not because they have flowed over time. This is essentially a "physics myth."

    - Warren
  7. Feb 15, 2004 #6
    thanks guys all your replies cleared up alot for me.

    yes i believe baker is right too, it is said that the labourers that built those structures would put the heavier end of the glass on the bottom side, usually being the thicker end.

    im sure you can see the logic in this =]
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