Inquisitive Stone Posted February 1, 2011 Posted February 1, 2011 Well, I've been thinking recently about the fact that I was always told that glass was a supercooled liquid. So I went online to do some research of my own and turned up with a conclusion that people still have no clue what glass really is. Also, all these terms like glass transition and some things about transistion phases. I'd really like some help in clearing up the mess about glass, and some explainantions. And maybe some conclusions and opinions of yours. Thanks guys.
swansont Posted February 1, 2011 Posted February 1, 2011 Amorphous solid. It doesn't have a "traditional" phase change from liquid to solid, so that causes some confusion. It has a … wait for it … glass transition. http://en.wikipedia.org/wiki/Glass_transition
mississippichem Posted February 1, 2011 Posted February 1, 2011 The silicon dioxide conglomerate particles are large enough and shaped so that they are prevented from being mobile enough to be a liquid and at the same time unable to lock into a rigid crystal lattice to form a true "solid" with a defined melting temperature. Check my blog, I had a short entry about this with a link to a relevant article.
Mr Skeptic Posted February 1, 2011 Posted February 1, 2011 It helps to know what terms mean. If glass was a supercooled fluid it could easily be disturbed with a nucleation site and form a crystalline structure, and like supercooled water would be still liquid. Glass doesn't do that. Some people thought glass was a viscous liquid, but there is no evidence of that. Contrary to myth, glass does not seem to flow, although it will if you heat it up enough to soften it. On the other hand, amorphous solid describes it very well, since glass has no specific crystalline structure and like a solid does not flow on its own. Me, I just call it glass.
imatfaal Posted February 2, 2011 Posted February 2, 2011 It helps to know what terms mean. If glass was a supercooled fluid it could easily be disturbed with a nucleation site and form a crystalline structure, and like supercooled water would be still liquid. Glass doesn't do that. Some people thought glass was a viscous liquid, but there is no evidence of that. Contrary to myth, glass does not seem to flow, although it will if you heat it up enough to soften it. On the other hand, amorphous solid describes it very well, since glass has no specific crystalline structure and like a solid does not flow on its own. Me, I just call it glass. "Contrary to myth, glass does not seem to flow" - Mr S - are you referring to the seeming thickening and distortion towards the bottom of panes of old glass, cos (although I won't assert a reason) lots of old glass does have a noticeable change. I work on a road with buildings that are all 300+ years old and listed - most of the glass is original and does seem to vary quite considerably down the pane (small panels around 8-12 inches wide by 15-18 inches high). It is possible this lack of uniformity was part of the manufacturing process 300 years ago and the panes were glazed in a manner to put the distortions at the bottom; but this anecdotal evidence would alternatively seem to be able to lend credence to the myth that you say is disproved.
Mr Skeptic Posted February 2, 2011 Posted February 2, 2011 "Contrary to myth, glass does not seem to flow" - Mr S - are you referring to the seeming thickening and distortion towards the bottom of panes of old glass, cos (although I won't assert a reason) lots of old glass does have a noticeable change. I work on a road with buildings that are all 300+ years old and listed - most of the glass is original and does seem to vary quite considerably down the pane (small panels around 8-12 inches wide by 15-18 inches high). It is possible this lack of uniformity was part of the manufacturing process 300 years ago and the panes were glazed in a manner to put the distortions at the bottom; but this anecdotal evidence would alternatively seem to be able to lend credence to the myth that you say is disproved. Yes, back in the day glass windows were not of uniform thickness. Usually when installing the window, the thicker part is placed on the bottom so that it isn't top-heavy. Some old installations have the thicker glass on top.
imatfaal Posted February 3, 2011 Posted February 3, 2011 Yes, back in the day glass windows were not of uniform thickness. Usually when installing the window, the thicker part is placed on the bottom so that it isn't top-heavy. Some old installations have the thicker glass on top. Appreciate that clarification. I always liked the idea that glass was flowing unbelievably slowly and causing the distortions on old glass; such a shame it isn't true.
alpha2cen Posted February 4, 2011 Posted February 4, 2011 (edited) Well, I've been thinking recently about the fact that I was always told that glass was a supercooled liquid. Thanks guys. The term "Supercooled liquid" has some problem. Supercooled means it is very cold and thermodynamically sufficient to be a solid crystal. It means far away from the transition state to solid state. Supercooled water means that the water is thermodynamically sufficient low temperature to be an ice, but there is no nucleus to be an ice. So, I think, it is better to state huge viscosity liquid at room temperature. Edited February 4, 2011 by alpha2cen
swansont Posted February 4, 2011 Posted February 4, 2011 The term "Supercooled liquid" has some problem. Supercooled means it is very cold and thermodynamically sufficient to be a solid crystal. But solid crystals don't have to be cold to form, so supercooled does not imply "very cold." So, I think, it is better to state huge viscosity liquid at room temperature. If you want to be consistent with accepted definitions, then no, it's not better.
alpha2cen Posted February 5, 2011 Posted February 5, 2011 (edited) But solid crystals don't have to be cold to form, so supercooled does not imply "very cold." This site provides you "supercooling" definition. http://en.wikipedia....ki/Supercooling There are no reports about old glass changes to glass crystal. Old building window glass have a flowing phenomena. And, high temperature glass have high viscosity, too. So,glass at the room temperature considers as very very high viscosity liquid. Edited February 5, 2011 by alpha2cen
swansont Posted February 5, 2011 Posted February 5, 2011 This site provides you "supercooling" definition. http://en.wikipedia....ki/Supercooling Glass is a solid above room temperature. Even if it were a supercooled liquid, it would not have to be "very cold" There are no reports about old glass changes to glass crystal. Which is further proof that it isn't a supercooled liquid. Old building window glass have a flowing phenomena. Did you read the rest of this thread? This is debunked above. And, high temperature glass have high viscosity, too. So,glass at the room temperature considers as very very high viscosity liquid. No, it's an amorphous solid. From the link in my very first post in the topic An amorphous solid that exhibits a glass transition is called a glass. Tar pitch is a high viscosity liquid http://en.wikipedia.org/wiki/Pitch_drop_experiment Does glass do that?
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