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-   -   Glass: Liquid or solid (http://www.physicsforums.com/showthread.php?t=9226)

mceddy2001 Nov19-03 02:57 PM

Glass: Liquid or solid
 
Ive heard some arguments for and against glass being a liquid. But what is it officially?

Mr. Robin Parsons Nov19-03 03:18 PM

An 'amorphis' liquid. (means 'without shape')

Moni Nov19-03 03:24 PM

It's also heard by me....

But first we have to purely define

WHAT IS SOLID AND WHAT IS LIQUID ???

What's your opinion?

Mr. Robin Parsons Nov19-03 03:30 PM

Quote:

Originally posted by Moni
It's also heard by me....
But first we have to purely define
WHAT IS SOLID AND WHAT IS LIQUID ???
What's your opinion?
It's NOT an opinion, 'solids' do not (generally speaking) change shapes, 'liquids' take on the shape of the vessel that they are deployed within, but do not change volume, as a 'gas' would......see chemistry; 101

BoulderHead Nov19-03 03:35 PM

Supercooled liquid is the way I had it explained to me.

LURCH Nov19-03 04:21 PM

It is my understanding that this entire debate get started because certain very large very old (400 years plus) panes of glass in the old cathedrals and the like were found to be significantly thicker at the bottom then they were at the top. This led to the conclusion that the glass was actually a highly viscous fluid and over its 400-500 years of existence was slowly "flowing" to the bottom of the pane.

However, I later heard that further research revealed some of 400-year-old panes of glass that were thicker at the top then at the bottom. Still others were thicker on the right side or the left.

Turns out, 400 years ago glassmakers simply did not have the technology to extrude a large pane of glass of uniform thickness. After that, I rather lost track of the subject.

Adrian Baker Nov19-03 05:56 PM

Quote:

Originally posted by LURCH
It is my understanding that this entire debate get started because certain very large very old (400 years plus) panes of glass in the old cathedrals and the like were found to be significantly thicker at the bottom then they were at the top. This led to the conclusion that the glass was actually a highly viscous fluid and over its 400-500 years of existence was slowly "flowing" to the bottom of the pane.

However, I later heard that further research revealed some of 400-year-old panes of glass that were thicker at the top then at the bottom. Still others were thicker on the right side or the left.

Turns out, 400 years ago glassmakers simply did not have the technology to extrude a large pane of glass of uniform thickness. After that, I rather lost track of the subject.


Too right. I'm sick of hearing that glass is a liquid. This is one of those stupid urban myths that just gets retold all the time. What other scientific 'fact' depends on the study of old artefacts. (actually I can think of many...but you know what I mean)
Evidence please!

BoulderHead Nov19-03 06:25 PM

Learn something new every day...
 
Interesting reading;

http://math.ucr.edu/home/baez/physic...***/glass.html

According to that site I may have to change my view.

benzun_1999 Nov20-03 05:53 AM

glass is a supercooled liquid.
 
Glass is amorphous substances that has no crystalline form. Amorphous substances can be thought of as supercooled liquids. The application of an external force over a period of time causes these materials to flow and become permanently deformed.

-Benzun
All for god.

russ_watters Nov20-03 08:34 AM

Re: Learn something new every day...
 
Quote:

Originally posted by BoulderHead
Interesting reading;

http://math.ucr.edu/home/baez/physic...***/glass.html

So essentially, glass isn't a solid or liquid, its a glass.

BoulderHead Nov20-03 08:39 AM

Pretty slick, heh?


Adrian Baker Nov20-03 08:58 AM

Yes - thats one way out of a conumdrum, redefine things!

And as I said - it DOESN'T flow!

Mr. Robin Parsons Nov20-03 09:24 AM

So I stand corrected.

mceddy2001 Nov20-03 10:42 AM

So.... A liquid can be defined as a substance that flows? How many liquids flow in outerspace and thefore would glass be a liquid if the gravity of the planet it was on, was not strong enough to accelerate the particles down towards the ground. At a certain pressure would glass be a solid and what is the freezing point of glass?

Chi Meson Nov20-03 01:07 PM

Quote:

Originally posted by mceddy2001
So.... A liquid can be defined as a substance that flows? How many liquids flow in outerspace and thefore would glass be a liquid if the gravity of the planet it was on, was not strong enough to accelerate the particles down towards the ground. At a certain pressure would glass be a solid and what is the freezing point of glass?
regular glass does not have a freezing point, per se. (and I'm talking about normal pressures; I don't know what the deal is in very high or very low pressures). Glass changes its viscocity as temperature increases. Most things do, but glass never hits a point where temperature stops going up while it melts. So the opposite is also true: temperture does not stop going down while it freezes.

So glass will go from a "solid" that will change its shape if pressure is applied slowly, to a thick fluid, to a thinner fluid, and etc.

By the way, a "fluid" is defined as anything that flows. THis includes gasses as well as liquids.

Adam Nov20-03 09:42 PM

The chemistry textbook in front of me classes glass as an amorphous solid. Same class as rubber and butter.

Mr. Robin Parsons Nov21-03 09:43 AM

Quote:

Originally posted by Adam
The chemistry textbook in front of me classes glass as an amorphous solid. Same class as rubber and butter.
Isn't that an oxymoron?

russ_watters Nov21-03 11:56 AM

Quote:

Originally posted by Mr. Robin Parsons
Isn't that an oxymoron?
No. "Amorphous" just means "Lacking distinct crystalline structure." Though most solids have a distinct chrystal structure, it isn't required. And even those that do have many flaws in the structure. A perfect chrystal is extremely difficult to achieve. However, given what we have seen in this thread, I'd say the definition of "glass" in Adam's textbook may be incomplete. What level is the book, Adam?


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