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Glass is classified as a :
Crystalline material
Amorphous solid
Polycrystalline
Composite
Amorphous solid
Glass is classified as an amorphous solid because its constituent particles lack a long-range repeating ordered structure. Unlike crystalline solids, which have a sharp melting point, glass softens over a range of temperatures.
Glass is classified as an amorphous solid because its constituent particles lack a long-range repeating ordered structure. Unlike crystalline solids, which have a sharp melting point, glass softens over a range of temperatures.
Think of a crystalline solid like a perfectly stacked pile of oranges in a grocery store, while glass is like a crowd of people who have suddenly frozen in place while moving chaotically.
SiO2тАЛ тАФ Chemical formula for pure silica (quartz glass)
╬ФHfusтАЛ тАФ Heat of fusion, which is sharp for crystalline solids but absent/diffuse for amorphous materials
Glass is formed by the rapid cooling of molten silica (SiO2тАЛ) or other inorganic mixtures. Because the cooling occurs too quickly for the atoms to arrange themselves into a stable lattice structure, they are 'frozen' in a disordered, liquid-like state. This is why glass is often referred to as a supercooled liquid.
Amorphous solids possess short-range order but lack long-range order.
They exhibit isotropic properties, meaning physical properties like refractive index are identical in all directions.
Glass does not have a defined geometric shape like crystals.
Upon heating, amorphous solids gradually soften rather than melting at a specific temperature.
Transparency due to lack of grain boundaries.
Tunable properties by adding oxides like Na2тАЛO or CaO.
Brittle nature leading to fracture under stress.
Lack of sharp melting point makes precise casting difficult.
Optical lenses and windows.
Fiber optics for telecommunications.
| Feature | Crystalline | Amorphous |
|---|---|---|
Structural Order | Long-range repeating pattern | Random, disordered arrangement |
Quartz (crystalline SiO2тАЛ) can be turned into fused silica (amorphous glass) by melting and rapid quenching.
Option A is wrong because crystals have well-defined periodic lattices.
Option C is wrong because polycrystalline materials are made of many small crystallites, which glass lacks.
Option D is wrong because composites are materials made from two or more constituent materials with significantly different properties.
B is correct тАФ Glass is an amorphous solid, a state of matter characterized by the absence of a long-range, ordered internal structure.
Always remember that 'anisotropic' properties (varying with direction) are a hallmark of crystals, whereas glass is 'isotropic'.
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