# Is glass a liquid, or a solid? **URL:** \ **Category:** Cecil's Columns/Staff Reports\ **Created:** [June 24, 2008, 12:59am UTC](https://boards.straightdope.com/t/is-glass-a-liquid-or-a-solid/453996 "2008-06-24T00:59:41Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [June 24, 2008, 12:59am UTC](https://boards.straightdope.com/t/is-glass-a-liquid-or-a-solid/453996/1 "2008-06-24T00:59:41Z")
[Cecil’s column](http://www.straightdope.com/classics/a1_120.html) [An article on MSNBC today](http://www.msnbc.msn.com/id/25335806/): > [@](#): > > Icosahedron jams > Some materials crystallize as they cool, arranging their atoms into a highly regular pattern called a lattice, Royall said, but although glass “wants” to be a crystal, as it cools the atoms become jammed in a nearly random arrangement, preventing it from forming a regular lattice. > > In the 1950s, Sir Charles Frank in the Physics Department at Bristol suggested that the arrangement of the “jam” should form what is known as an icosahedron, but at the time he was unable to prove it. > > An icosahedron is like a 3-D pentagon, and just as you cannot tile a floor with pentagons, you cannot fill 3-D space with icosahedrons, Royall explained. That is, you can’t make a lattice out of pentagons. > > When it comes to glass, Frank thought, there is a competition between crystal formation and pentagons that prevents the construction of a crystal. If you cool a liquid down and it makes a lot of pentagons and the pentagons survive, the crystal cannot form. > > It turns out that Frank was right… ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [June 24, 2008, 1:34am UTC](https://boards.straightdope.com/t/is-glass-a-liquid-or-a-solid/453996/2 "2008-06-24T01:34:03Z")
I’m not sure I’d put too much stock in that article, since they repeat the tired myth about medieval window glass showing sings of sagging. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [June 24, 2008, 1:36am UTC](https://boards.straightdope.com/t/is-glass-a-liquid-or-a-solid/453996/3 "2008-06-24T01:36:42Z")
[QUOTE=Q.E.D.] I’m not sure I’d put too much stock in that article, since they repeat the tired myth about medieval window glass showing sings of sagging. [/QUOTE] I noticed that. ---
**Author:** ![WarmNPrickly](https://avatars.discourse-cdn.com/v4/letter/w/d78d45/32.png) [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)\ **Post date:** [June 24, 2008, 4:18am UTC](https://boards.straightdope.com/t/is-glass-a-liquid-or-a-solid/453996/4 "2008-06-24T04:18:37Z")
I think it really comes down to definitions. Cecil says some mathemetician did the calculations to determine that glass would thicken 5% at the base over 10 million years. First of all, lets keep in mind that computer modeling isn’t any where near that good. Whatever calculation she did used many assumptions and fudge factors. I’m not saying it wasn’t a reasonable estimate, but I wouldn’t reference it in a paper. _Discover Magazine_ isn’t exactly the same caliber as _Nature_. I would take that estimate with a whole shaker of salt. Strangely, I would call glass a glass. I would define a glass as an amorphous solid. It is different from a crystalline solid and it has some characteristics of a liquid. Still, I think calling glass a liquid reaks of fact dropping to prove your smart. For almost all real world applications, glass behaves like a solid. Plus, calling it a liquid confirms peoples mistaken idea that medeivel windows are sagging. ---
**Author:** ![DSYoungEsq](https://avatars.discourse-cdn.com/v4/letter/d/c6cbf5/32.png) [@DSYoungEsq](https://boards.straightdope.com/u/DSYoungEsq)\ **Post date:** [June 24, 2008, 4:48pm UTC](https://boards.straightdope.com/t/is-glass-a-liquid-or-a-solid/453996/5 "2008-06-24T16:48:23Z")
[We address the issue previously.](http://boards.straightdope.com/sdmb/showthread.php?t=433958&highlight=glass+amorphous) [We address it before that](http://boards.straightdope.com/sdmb/showthread.php?t=329054&highlight=glass+amorphous) And numerous times before that, too many to make links for. ETA: [Ok, I’ll add one more time we discussed it.](http://boards.straightdope.com/sdmb/showthread.php?t=142582&highlight=glass+liquid+solid+windows) ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [June 24, 2008, 5:03pm UTC](https://boards.straightdope.com/t/is-glass-a-liquid-or-a-solid/453996/6 "2008-06-24T17:03:47Z")
Glass is a liquid in the same sense that it’s an electrical conductor. Yes, it has a finite viscosity, but it also has a finite resistivity. It’s just that both of them, while finite, are still really, really high. So if you’re going to divide substances into “liquid” and “solid” based on their viscosity, or into “conductors” and “insulators” based on their resistivity, then it makes sense to call glass a solid and an insulator. ---
**Author:** ![SeanArenas](https://avatars.discourse-cdn.com/v4/letter/s/df705f/32.png) [@SeanArenas](https://boards.straightdope.com/u/SeanArenas)\ **Post date:** [June 24, 2008, 11:30pm UTC](https://boards.straightdope.com/t/is-glass-a-liquid-or-a-solid/453996/7 "2008-06-24T23:30:28Z")
It depends on how you define liquid from solid. Is anything that can be made liquid at a temperature before it combusts considered a liquid? Is it considered a liquid because it is a liquid at most temperatures we’re likely to deal with it at? Is it a liquid because more of it’s liquid than solid on this planet right now? Where exactly is the definition? Perhaps it’s a solid because of the type of crystalline structure after it forms? That’s like saying that metal is a liquid because it’s liquid at certain temperatures. “Really, really high ones?” “Sometimes … what about mercury?” What about water - there’s plenty of it in a solid state right now … and what about “rocks” ? Solid or liquid? I wonder what percentage of the earth is made of solid “rock”-like material, and what is liquid (right now)? ---
**Author:** ![Rhubarb](https://avatars.discourse-cdn.com/v4/letter/r/59ef9b/32.png) [@Rhubarb](https://boards.straightdope.com/u/Rhubarb)\ **Post date:** [June 25, 2008, 2:47am UTC](https://boards.straightdope.com/t/is-glass-a-liquid-or-a-solid/453996/8 "2008-06-25T02:47:48Z")
[QUOTE=SeanArenas] It depends on how you define liquid from solid. Is anything that can be made liquid at a temperature before it combusts considered a liquid? Is it considered a liquid because it is a liquid at most temperatures we’re likely to deal with it at? Is it a liquid because more of it’s liquid than solid on this planet right now? Where exactly is the definition? Perhaps it’s a solid because of the type of crystalline structure after it forms? That’s like saying that metal is a liquid because it’s liquid at certain temperatures. “Really, really high ones?” “Sometimes … what about mercury?” What about water - there’s plenty of it in a solid state right now … and what about “rocks” ? Solid or liquid? I wonder what percentage of the earth is made of solid “rock”-like material, and what is liquid (right now)? [/QUOTE] The liquid and solid determinations are made at STP - Standard Temperature and Pressure, which would be 25 °C and 760 mm Hg (298 K, 101.5 kPa), or in some instances at a specifically defined condition. So glass is a solid, albeit an amorphous one, at standard conditions. ---
**Author:** ![Saint\_Cad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saint_cad/32/18907_2.png) [@Saint\_Cad](https://boards.straightdope.com/u/Saint_Cad)\ **Post date:** [June 28, 2008, 8:48am UTC](https://boards.straightdope.com/t/is-glass-a-liquid-or-a-solid/453996/9 "2008-06-28T08:48:36Z")
Then what is [pitch](http://www.physics.uq.edu.au/pitchdrop/pitchdrop.shtml)? ---
**Author:** ![Contrapuntal](https://avatars.discourse-cdn.com/v4/letter/c/e274bd/32.png) [@Contrapuntal](https://boards.straightdope.com/u/Contrapuntal)\ **Post date:** [June 28, 2008, 12:16pm UTC](https://boards.straightdope.com/t/is-glass-a-liquid-or-a-solid/453996/10 "2008-06-28T12:16:28Z")
[QUOTE=Saint Cad] Then what is [pitch](http://www.physics.uq.edu.au/pitchdrop/pitchdrop.shtml)? [/QUOTE] That’s kind of a screwball experiment. ---
**Author:** ![andros](https://avatars.discourse-cdn.com/v4/letter/a/e480ec/32.png) [@andros](https://boards.straightdope.com/u/andros)\ **Post date:** [June 29, 2008, 11:01pm UTC](https://boards.straightdope.com/t/is-glass-a-liquid-or-a-solid/453996/11 "2008-06-29T23:01:02Z")
. How is is screwball? . ---
**Author:** ![DSYoungEsq](https://avatars.discourse-cdn.com/v4/letter/d/c6cbf5/32.png) [@DSYoungEsq](https://boards.straightdope.com/u/DSYoungEsq)\ **Post date:** [June 29, 2008, 11:21pm UTC](https://boards.straightdope.com/t/is-glass-a-liquid-or-a-solid/453996/12 "2008-06-29T23:21:28Z")
[QUOTE=andros] . How is is screwball? . [/QUOTE] A “screwball” is a type of [pitch](http://en.wikipedia.org/wiki/Pitch_%28baseball%29). ---
**Author:** ![andros](https://avatars.discourse-cdn.com/v4/letter/a/e480ec/32.png) [@andros](https://boards.straightdope.com/u/andros)\ **Post date:** [June 30, 2008, 4:39pm UTC](https://boards.straightdope.com/t/is-glass-a-liquid-or-a-solid/453996/13 "2008-06-30T16:39:18Z")
. Hmmm. I’ll accept the whoosh, but I think it’s a stretch. . ---
**Author:** ![WhyNot](https://avatars.discourse-cdn.com/v4/letter/w/c77e96/32.png) [@WhyNot](https://boards.straightdope.com/u/WhyNot)\ **Post date:** [June 30, 2008, 5:13pm UTC](https://boards.straightdope.com/t/is-glass-a-liquid-or-a-solid/453996/14 "2008-06-30T17:13:41Z")
[QUOTE=SeanArenas] It depends on how you define liquid from solid. [/quote] My chem101 teacher defined states of matter as follows: A solid is a substance with a definite volume and a definite shape A liquid is a substance with a definite volume and no definite shape A gas is a substance with no definite volume and no definite shape While this may be oversimplifying when you get into higher levels of chemistry and physics, it’s certainly clear enough for an article written for laypeople. Laypeople can recognize that heated, molten glass is certainly a liquid. What they’re addressing is glass at room temperature. So once again, we’re back to the question - does glass at room temperature change shape? Most people say no, or not at rates meaningful within a human lifespan, and so therefore we might as well call it a solid. > [@](#): > > Is anything that can be made liquid at a temperature before it combusts considered a liquid? Yes, it is liquid at that temperature. Any element which maintains its molecular stability can be made gas, solid or liquid by changing the temperature and/or pressure. (In theory, anyway, I’m not sure if it’s practical to do so for all substances.) > [@](#): > > Is it considered a liquid because it is a liquid at most temperatures we’re likely to deal with it at? Nothing is always a liquid. You need to be more specific about the substance, temperature and pressure. Are we talking about water? Water, unlike most things, is found on our planet, without human fiddling, in all three forms. Water isn’t a liquid, water is \*sometimes \*a liquid. Sometimes it’s a gas and sometimes a solid. In my kitchen, it’s found in all three forms at once. > [@](#): > > Is it a liquid because more of it’s liquid than solid on this planet right now? Where exactly is the definition? See above. It has nothing to do with quantity, only the properties of the specific sample in question. “Water is liquid” is a meaningless and false statement. “This sample of water is liquid.” or “Water is liquid between 1 and 99 degrees Centigrade at 1 atm” are meaningful statements. > [@](#): > > That’s like saying that metal is a liquid because it’s liquid at certain temperatures. “Really, really high ones?” “Sometimes … what about mercury?” Metals can be liquid, although each has its own temperature at which it becomes liquid. “Metals” is not a substance, it’s a group of substances which have certain characteristics in common (they are shiny, they conduct electricity, they are generally (but not always) solid at STP and they generally (but not always) have a relatively high melting point when compared to non-metals and metaloids. > [@](#): > > What about water - there’s plenty of it in a solid state right now … and what about “rocks” ? “Water” doesn’t tell us enough - we need the temperature and pressure to determine the state. “Rocks” is, again, not a substance. You must be more specific about the substance and the temperature and pressure. ---
**Author:** ![Contrapuntal](https://avatars.discourse-cdn.com/v4/letter/c/e274bd/32.png) [@Contrapuntal](https://boards.straightdope.com/u/Contrapuntal)\ **Post date:** [July 1, 2008, 7:27pm UTC](https://boards.straightdope.com/t/is-glass-a-liquid-or-a-solid/453996/15 "2008-07-01T19:27:55Z")
[QUOTE=andros] . Hmmm. I’ll accept the whoosh, but I think it’s a stretch. . [/QUOTE] Only if there’s a man on base. ---
**Author:** ![mlees](https://avatars.discourse-cdn.com/v4/letter/m/ba8739/32.png) [@mlees](https://boards.straightdope.com/u/mlees)\ **Post date:** [July 1, 2008, 7:52pm UTC](https://boards.straightdope.com/t/is-glass-a-liquid-or-a-solid/453996/16 "2008-07-01T19:52:58Z")
[QUOTE=Saint Cad] Then what is [pitch](http://www.physics.uq.edu.au/pitchdrop/pitchdrop.shtml)? [/QUOTE] A little over one drop per decade. Wow! ---
**Author:** ![FoieGrasIsEvil](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/foiegrasisevil/32/16638_2.png) [@FoieGrasIsEvil](https://boards.straightdope.com/u/FoieGrasIsEvil)\ **Post date:** [July 2, 2008, 5:44pm UTC](https://boards.straightdope.com/t/is-glass-a-liquid-or-a-solid/453996/17 "2008-07-02T17:44:53Z")
Glass is a liquid? What, are you going to tell me a tomato is a fruit next? ---
**Author:** ![WhyNot](https://avatars.discourse-cdn.com/v4/letter/w/c77e96/32.png) [@WhyNot](https://boards.straightdope.com/u/WhyNot)\ **Post date:** [July 2, 2008, 5:59pm UTC](https://boards.straightdope.com/t/is-glass-a-liquid-or-a-solid/453996/18 "2008-07-02T17:59:05Z")
[QUOTE=FoieGrasIsEvil] Glass is a liquid? What, are you going to tell me a tomato is a fruit next? [/QUOTE] Yep! But that’s okay, 'cause pineapple isn’t. (Nor does it grow on trees.) ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [July 2, 2008, 6:38pm UTC](https://boards.straightdope.com/t/is-glass-a-liquid-or-a-solid/453996/19 "2008-07-02T18:38:25Z")
> [@](#): > > What, are you going to tell me a tomato is a fruit next? I don’t get it. Nobody ever asks “Is a carrot a vegetable, or a root?”, or “Is lettuce a vegetable, or a leaf?”. But both of those questions have exactly the same structure as “Is a tomato a vegetable, or a fruit?”. For that matter, nobody ever seems to ask the vegetable/fruit question about peppers, cucumbers, eggplants, green beans, or any of the other fruit vegetables, either. It’s only ever tomatoes. ---
**Author:** ![Half\_Man\_Half\_Wit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/half_man_half_wit/32/21766_2.png) [@Half\_Man\_Half\_Wit](https://boards.straightdope.com/u/Half_Man_Half_Wit)\ **Post date:** [July 2, 2008, 11:51pm UTC](https://boards.straightdope.com/t/is-glass-a-liquid-or-a-solid/453996/20 "2008-07-02T23:51:44Z")
I’d say that for most, if not all, practical considerations the question of whether or not glass is a liquid is pretty moot. Except, of course, as a stoner conversation topic: Stoner A: “Dude, did you know that glass is, like, a liquid?” Stoner B: “No way, man!” _pause as the topic is briefly forgotten_ Stoner A: _pours some water into a glass_ Stoner B: “Dude…” Stoner A: “What?” Stoner B: “You just, like, poured a liquid into another liquid!” Stoner A: “…Whoa. Far out, man.” Stoner A: _proceeds to take a sip_ Stoner B: “I mean, how can you even do that?” Stoner A: “Do what?” Stoner B: “Drink _one_ liquid, but not the _other_!” _astonished silence_ Stoner A: “That must be why it’s called ‘drinking a glass of water’!” Stoner B: “But now… is it half full, or half empty?” Stoner A: “Oh, just shut up.” This is totally not based on a conversation I once had with a friend. Don’t take drugs, kids! [Next page](https://boards.straightdope.com/t/is-glass-a-liquid-or-a-solid/453996.md?page=2)