Is glass a liquid or solid?

Hi kylemac:

Despite what "urban legends" say, glass is most definitely a solid,
not some sort of weird, supercooled liquid.

In particular, glass is an amorphous solid:

amorphous
URL: http://dictionary.reference.com/search?q=amorphous
Quote: "Lacking distinct crystalline structure"

The following websites provide details. 

Glass: Liquid or Solid -- Science vs. an Urban Legend
URL: http://dwb.unl.edu/Teacher/NSF/C01/C01Links/www.ualberta.ca/~bderksen/florin.html
Quote: "Glasses are amorphous solids. There is a fundamental
structural divide between amorphous solids (including glasses) and
crystalline solids. Structurally, glasses are similar to liquids, but
that doesn't mean they are liquid. It is possible that the 'glass is a
liquid' urban legend originated with a misreading of a German treatise
on glass thermodynamics."
Note: Read the section "What the Scientists Say."

Search Strategy (on Google):
* glass solid liquid

I hope this helps. 

websearcher

This question is in physics FAQ and different people give different answers.

Other views are described here:
http://answers.google.com/answers/threadview?id=419211
 
In particular it says:
 Different disciplines define terms 'solid' and 'liquid' differently. 
Answer to question (is it a liquid?) depends on definition of liquid.
However, proper discipline for this issue is a bit esoteric field of
material science called Rheology (science of flow).
http://dmoz.org/Science/Physics/Rheology/

 According to this discipline classification 'amorhphous vs crystaline'
 differs from the classification by phase of the material (solid liguid gas):

 Crystals can be solid or liquid and so can be amorphous materials.
 All four combinations exist, but some are rare.
 
Quantitatively - from point of view of material science:
 Crystalinity reffers to 'structure' (a microscopic property), defined
by 'correlation length of order of arrangemenet of atoms' and measured
e.g. by X-ray diffraction.

Phases are classified by 'properties' by 'material functions' of
viscosity and compressibility and measured in macroscopic experiments.

 In everyday life most liquids have structures with short correlation
length, which leads to confusion of these two different properties.
However, even in common language, most people would agree that 'molten
glass' and 'liquid crystals' are both liquids and 'amorphous solids'
are solids.
At least I hope so.

glass is a solid.  but what kind of solid.  it is not crystalline but
amorphous.  to better explain this, both, ruby and glass are solids
but ruby has has a crystalline lattice which has alumina molecules in
it aligned lie in a particular fashion, called the unit cell, and that
particular unit cell repeats itself throughout the 3D space.  whereas
glass does not have any such uniformity - SiO2 (silica)molecules in
them lie in all possible directions and there is no repatability -
because of which it is called "super cooled liquid".  I think the term
supercooled liquid is justified because glass that is solid now will
be a liquid at say 2000 degrees C similar to any liquid that may be
cooled to sub 0 degrees and may not have a crystal lattice.  it is a
super cooled liquid.  where as ice is not supercooled liquid because
they align themselves in an orderly fashion to form a regular 3D
lattice.  Hence ice is not supercooled liquid (though a solid) instead
a crystalline substance.

There are two comments to this question

From: hedgie-ga on 06 Jun 2005 17:59 PDT
From: sciencewiz-ga on 12 Jul 2005 13:08 PDT 

2nd comment by "science wiz" repeates lot of cliches which
1st comment attempted to show to be common errors.

I will therefore summarise the 1st comment in more simple language:

 Solid vs liquid is a different classification then crystaline vs amorphous
 Everybody agrees that glass is amorphous. 
That has nothing to do with it being liquid or solid.

There are different definition of 'solid' and so there is no absolute answer.
Most 'scientific' definition is provided by Rheology (science of flow) .
According to this definition

                     Glass is a viscoelastic liquid

PLASTICS (polymers) ARE CLASSIFIED as thermosets (viscoelastic solids)
                              and     thermoplasts (viscoelastic liquids).

 Examples are vulcanised and unvulcanised rubber -- both flow, but flow
 differently. First is solid, the second a liquid. You can learn more
 about the subtle difference in books on Rheology:
 http://www.ipolytech.com/UKrheology.htm

Glass has very high viscosity E15 Pas and so, at normal temperature
and reasonable time of observation its flow properties are not measurable.

At increased temperature the glass flow can be measured and the difference
between viscoelastic solids and liquids becomes apparent.

The 'supercooled liquid' adjective is not applicable here.
That term describes  metastable pahse, as described here
http://chemserv.bc.edu/Department/faculty/fourkas/Super.html

I am aware that many people consider 'glass is a liquid' an urban legend
http://dwb.unl.edu/Teacher/NSF/C01/C01Links/www.ualberta.ca/~bderksen/florin.html
   
neverthless, the arguments presented there do not address the scientific facts
which I have presented here.
If you do want to argue this point, kindly, at least, read the
references I have listed in my first comment.
 

Hedgie