Glass- Solid or Liquid??

Question

Is glass really a solid or a liquid? I've seen old glass that looked like it was dripping, but it was still really hard. And how can a liquid crack? Also, if it was a liquid, how come we can't put our hand or foot or whatever through it easily like we can with water? Yeah we can do it easily but it'd break. I think it's a solid, but I am curious to know other's opinions.

Answer 1

its a very slow moving liquid

Answer 2

Good question.

In a "zero-gravity" atmosphere, if you spurt drops of water into the air, the water droplets will stay stay together and float around like little sphere.

Why is this? Its because there is no aparrent force (gravity, atmospheric pressure) present. If you do this on Earth, the water will drop to the ground and flow.

All materials ("solids, gases, liquids") are subject to to flowing in the presence of a force, some materials require a much greater force than others until you can see a response though. Look at chocolate, if its in a candy bar, its solid. When you put some pressure on it, it'll eventually melt and flow.

In the case of glass, gravity and atmospheric pressure are acting upon it. The force is making the glass reorder and go to a lower thermodynamic state.

So in essence, its a solid that flows (very slowly) or a highly viscous liquid (which has been said before), its all semantics.

Answer 3

Here's one answer:

"There is no clear answer to the question "Is glass solid or liquid?". In terms of molecular dynamics and thermodynamics it is possible to justify various different views that it is a highly viscous liquid, an amorphous solid, or simply that glass is another state of matter which is neither liquid nor solid. The difference is semantic. In terms of its material properties we can do little better. There is no clear definition of the distinction between solids and highly viscous liquids. All such phases or states of matter are idealisations of real material properties. Nevertheless, from a more common sense point of view, glass should be considered a solid since it is rigid according to every day experience. The use of the term "supercooled liquid" to describe glass still persists, but is considered by many to be an unfortunate misnomer that should be avoided. In any case, claims that glass panes in old windows have deformed due to glass flow have never been substantiated."
http://math.ucr.edu/home/baez/physics/General/Glass/glass.html

JMB

Answer 4

Solid. More or less.

Ordinary glass does NOT flow. For example, ancient Roman glass has been found in its original shape and form.

The idea that glass flows is a persistent myth. Much old glass LOOKS like it has flowed, because it WAS liquid when it was heated and made, and assumed a "flow" like shape as it cooled. Old windows made with older methods of manufacture often cooled with "waves" or inconsistencies in thickness. Once it cooled, however, it became an amorphous non-crystalline solid.

Granted, the distinction between a highly viscous liquid and an amorphous solid is somewhat arbirtrary, but it is easy enough to show that ordinary glass does not "flow" or show other properties commonly associated with fluids.

Answer 5

Glass is a very cold liquid in some senses: it's composition is not crystaline but amorphic. However, the story about it flowing is hokum. Old glass was produced by - well - old methods. Rather than being rolled as it is today, it was pressed or drawn, the latter being a common process; it resulted in ripples and air bubbles in the finished product. Perhaps that's why this idea started.

Answer 6

How can a liquid crack? Ever see crushed ice? The viscosity of glass is much stiffer than that of liquid water. Mercury at room temperature is also a liquid, but it sure isn't the same as water. The key to your question is in the word "viscous" or "viscosity" - check it out!

Answer 7

Glass is classified as a super-viscous liquid. Over time, glass will succumb to outside forces and distort. If the force is applied too quickly, the glass can't distort fast enough to dissipate the energy and cracks form.

Everyone knows what will happen if you hit a piece of glass with a hammer...it shatters, right? But if you apply the same impact energy over a long period, the glass will just flatten.

We've all played with Silly Putty at one time or another...it's very plaible, very putty-like. Get a lump of silly Putty and whack it with a hammer. If it's not too warm, it will shatter like glass....or, if you prefer, like a super-viscous liquid.

Answer 8

It's a solid, it just acts like a liquid over long periods of time. Most other solids do the same thing, glass just does it over the course of decades rather than eons. It's a solid, just a little more liquid than most solids (just as molasses is a liquid, just a little more solid than most liquids :P).

Answer 9

It's a solid but is still subject to the laws of gravity... Very old windows in old buildings can be brittle at the top because some of the glass has flowed to the bottom of the window... This happens over the course of many years....

Answer 10

It's a highly viscous liquid! It flows very slowly indeed so you don't even notice it. It has more order than most liquids but it's crystalline structure is not ordered enough to classify it as a solid.

Answer 11

Glass is a solid. It is a liquid when its being made, but ends up as a solid.