Question

Explain crystalline solids and amorphous solids.

Answer 1

i. Crystalline solids:

a. A crystalline solid usually consists of a large number of small crystals, each of them having a definite characteristic geometrical shape. These tiny crystals are called unit cells.

b. A unit cell is a basic repeating structural unit of a crystalline solid.

c. Crystalline solids have long range order which means that there is a regular pattern of arrangement of particles (atoms, ions or molecules) which repeats itself periodically over the entire crystal.

eg. Sodium chloride and quartz

ii. Amorphous solids:

a. The arrangement of constituent particles (atoms, molecules or ions) in amorphous solids has only short range order. 

b. In such an arrangement, a regular and periodically repeating pattern is observed over short distances only. 

c. Such portions are scattered and in between, arrangement is disordered.

eg. glass, rubber, plastics and amorphous silicon.

Answer 2

Crystalline solids have well-defined edges and faces, diffract x-rays, and tend to have sharp melting points. In contrast, amorphous solids have irregular or curved surfaces, do not give well-resolved x-ray diffraction patterns, and melt over a wide range of temperatures

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