Question

Which of the following materials is the best example of Amorphous material
1. Silver
2. Brass
3. Mica
4. Glass

Answer 1

Correct Answer - Option 4 : Glass

Explanation:

Amorphous material:

• An amorphous material (AM) has a non-crystalline structure that differs from that of its iso-chemical liquid and does not undergo structural relaxation and the glass transition when heated. Examples are: Glass, Gels, plastics, various polymers, wax, thin films.
• The terms amorphous and non-crystalline are synonymous under this definition. The term glassy has the same structural meaning, but besides it also usually implies that the material exhibits a ‘glass transition’. Although the presence of dynamic disorder in the case of liquids complicates matters, the average atomic structure of liquids can be described in similar ways to that of amorphous solids.
• Amorphous alloys are a class of metal alloy that, unlike ordinary metals do not have a long-range crystal structure.
• Amorphous alloys have no grain boundaries.

Properties of Amorphous Solids:

Amorphous solid are sometimes described as supercooled liquid because their molecules are arranged randomly somewhat as in a liquid state.

1. Lack of long-range order: Amorphous Solid does not have a long-range order of arrangement of their constituent particles. However, they may possess small regions of orderly arrangement. These crystalline parts of an otherwise amorphous solid are known as crystallites.
2. No sharp melting point: An amorphous solid does not have a sharp melting point but melts over a range of temperatures. For example, glass on heating first softens and then melts over a temperature range. Glass, therefore, can be molded or blown into various shapes. Amorphous solid does not possess the characteristic heat of fusion.
3. Conversion into a crystalline form: Amorphous solid, when heated and then cooled slowly by annealing, becomes crystalline at some temperature. That is why glass objects of ancient times look milky because of some crystallization having taken place.

Difference between Crystalline and Amorphous Solid:

Properties	Crystalline solid	Amorphous solid
Structure	The constituent particles, atoms, ions, or molecules are arranged in regular and definite three-dimensional patterns. For example, sodium chloride, diamond, sugar, etc.	The constituent particles are arranged in irregular three-dimensional patterns.
Cutting with a knife	Gives clean, sharp cleavage.	Unclean cleavage.
Compressibility	Rigid and incompressible	Usually rigid and cannot be compressed to any appreciable extent.
Melting point	They have a sharp and definite melting point.	The melting point is not definite. Melt over a range of temperatures.
Heat of fusion	Definite	Not definite.
Physical properties	These are anisotropic in that their physical properties are not identical in all directions.	These are isotropic, that is their physical properties are identical in all directions.