Why is glass brittle?
930979
If you are talking about regular soda-lime glass, the reason why it is brittle is because its molecular structure resembles that of a liquid.  HOWEVER, it does not have a liquid structure.  Glass is composed of tetrahedral crystals.  That these crystals did not achieve regular, repeating crystalline structure does not mean glass is a permanent liquid.  My Glass Ceramics prof nearly shot me for saying that in class one day.\n\nBut that's exactly it:  Glass is brittle because it does not have good large-area orderly crystalline structure.  If it did, it would be like sheetmetal steel, where it dents and deforms instead of shattering.\n\nI would like to point out something else though:  The strongest fiber ever tested was a glass fiber drawn and tested in an inert atmosphere.  Also, you can take a glass fiber by the ends and bend it into a circle, much like any metal wire.  Hence it is elastic.  BUT if you touch that same fiber in several places, then try to bend it again it will shatter in your hands.
353454
Depending on it's composition, it can have a melting point of about 1400-1600 °C. However, there are glasses that will melt at lower temperatures but those are not common among commercial nor industrial usage.
77153
Glass is composed of mainly silicone, heated to a high temperature until it forms a supercooled liquid. Sand is the most common form of raw material used in making glass though silica is sometimes used. Other materials can be added in to give extra strength or changes in its composition to make specialized products such as pyrex, coloration and certain metals are added to add colour to it.
385147
As you've realised, glass isn't totally transparent. It lets through most frequencies of light in the VISIBLE region of the spectrum, but blocks UV. \n\nSo glass is just like a blue piece of transparent plastic. The plastic is blue because it only lets through the blue visible light and blocks everything else. The only difference with glass is that it blocks the UV and lets most of the visible spectrum through.\n\nAt the atomic level, transparency occurs because atoms, and the electrons whizzing round them, have particular (or "discrete") energy levels. Only light of the correct frequencies can actually interact with atoms, and excite the electrons to a higher energy level, in which case the light of that frequency is absorbed. \n\nThe energy levels that exist in glass are such that UV light can excite the electrons and therefore gets absorbed, whereas for visible light there aren't any electrons that can absorb that frequency and get excited, so the visible light effectively passes straight through.
525142
Plastic vs. Glass\nfirst off it isn't too fair to compare plastic to glass. You're comparing a category of materials against one single material. Plastics have almost an infinite range of properties where as glass has one set of properties. There are some plastics such, as acrylics, that behave very similarly as glass with respect to impact strength, clarity, etc. And there are some plastic that behave nothing like glass. Such as polyurethane, very ductile and rubbery even. \nTo conclude, depending on the plastic there can be many differences between plastic and glass, or they can be quite similar.
960255
Tempering can cause glass to explode. Tempering means that there are internal stresses within the glass that result from uneven cooling from its molten state during the manufacturing process due to the glass's thermal expansion characteristics. This can occur due to carelessness or intentionally. So called "safety glass", like that used in autos, is intentionally tempered. If the glass is even slightly nicked, the tempering resulting is stress concentration that can cause a chain reaction releasing all the stress in the glass  in a great low energy "explosion" of glass pellets. The idea is that no one shard of broken glass is large enough to cause serious injury.
390529
If the unmovable object is not unbreakable, it WILL be broken. \nI believe this is an unanswerable question.
1128
This is pretty much a question of the definition you are using.\n\nIn a strict definition, conventional solids have a crystalline structure. Under this definition, glass is a supercooled, highly viscous liquid rather than a conventional (crystalline) solid. \n\nIn many ways, glass acts like a solid. Using that behaviour as a criterion, glass is a solid.
623497
Glass and SiO2 are chemically same. But the glass is sytematic arrangement of atomic structure and can happen as a slow physical process
672330
Glass is made from silica and sand, heated at very high temperatures.  Different colors come from adding different metals and other elements.
58505
The surface temperature of the glass is lower than that of your hand, thus causing the expansion of the molecules to compensate in order to equalize the surface tension in both the glass and your hand.
1068890
carbon steel will become brittle and break easily of it is subjected to high temperatures. It requires further heat treatment (tempering) to make it a bit softer and reduce brittleness.
151415
It is sometimes said that glass in very old churches is thicker at the bottom than at the top because glass is a liquid, and so over several centuries it has flowed towards the bottom.  This is not true.  In Mediaeval times panes of glass were often made by the Crown glass process.  A lump of molten glass was rolled, blown, expanded, flattened and finally spun into a disc before being cut into panes.  The sheets were thicker towards the edge of the disc and were usually installed with the heavier side at the bottom.  Other techniques of forming glass panes have been used but it is only the relatively recent float glass processes which have produced good quality flat sheets of glass.\n\nTo answer the question "Is glass liquid or solid?" we have to understand its thermodynamic and material properties.\n\nThermodynamics of glass\n\nThere is still much about the molecular physics and thermodynamics of glass that is not well understood, but we can give a general account of what is thought to be the case.\n\nMany solids have a crystalline structure on microscopic scales.  The molecules are arranged in a regular lattice.  As the solid is heated the molecules vibrate about their position in the lattice until, at the melting point, the crystal breaks down and the molecules start to flow.  There is a sharp distinction between the solid and the liquid state, that is separated by a first order phase transition, i.e. a discontinuous change in the properties of the material such as density.  Freezing is marked by a release of heat known as the heat of fusion. \n...\nConclusion\n\nThere 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.  Examples of Roman glassware and calculations based on measurements of glass visco-properties indicate that these claims cannot be true.  The observed features are more easily explained as a result of the imperfect methods used to make glass window panes before the float glass process was invented.
1006328
Because of the difference in the index of refraction, with everything else equal, the glass should be brighter because it is less diffuse.\n\n\nhttp://www.findarticles.com/p/articles/mi_rlg4413/is_SLGG0003/ai_n15607430\n\nhttp://www.madsci.org/posts/archives/Jan2003/1042659817.Ph.r.html
372151
If you tint it, it adds to the heat being absorbed to the glass.  Dark things absorb more light, light colors reflect more.  So the window should then start becoming hotter than before and hence why you should start seeing it crack now.  Also is the window facing east, it would explain the time of day it is cracking.  Now the window will not only heat to a high temperature, it will do it faster from the however cold it will have gotten overnight.
273848
There are many types of glass. Different mixures creates different optical densities. These different optical densities will make the refractive index of glass vary. However, in GCSE 'O' Level, the refractive index of glass is usually 1.5. (hope this helps you)
973045
Concrete, as it cures, forms a complex and insoluble "crystalline" structure.  Crystalline materials such as this have atoms that are more or less "locked" in place by the kinds of chemical bonds that formed during the curing process.  Since the atoms are more or less fixed in space relative to one another, they can't slip and slide to dissipate stresses.  So, when a large enough force is applied, the strong chemical bonds finally break and a "brittle fracture" occurs.  One observes concrete shatter, creating splinters and dust, and the material is described as brittle.