Crystalline & Amorphous Solid – Definitions and it’s Examples – NeetHelp

Solids can be broadly classified into two categories according to it’s crystal structure.

  1. Crystalline Solid
  2. Amorphous Solid
Types of solids

Crystalline Solid

  • In a crystalline solid the structural units (atoms molecules or ions) are arranged in a definite pattern.
  • This definite pattern is repeated constantly throughout the solid. on account of the constant repetition of this definite pattern, a crystalline solid has a definite geometrical configuration which is characteristic of the nature of the substance.
  • Crystalline solid possess sharp melting points and characteristic heat of fusion. If a molten crystalline solid is cooled, the original geometric configuration reappears again.
  • These solids are incompressible.
  • They possess planar surface and characteristics angles between the faces. A crystalline solids can be cleaved only a long definite planes and on cleavage gives a clean cut.
  • The crystalline solid are anisotropic in nature, that is they may possess different magnitudes of physical properties in different direction.
  • Crystalline solids are regarded as true solids
Crystaline solid

Examples – Table Salt (NaCl), sugar (sucrose), Diamond, Quartz, Silver iodide

Amorphous Solids

  • In an amorphous solid the structural units are not arranged in a definite pattern.
  • In an amorphous solid there may be and orderly arrangement of its structural units, but this arrangement is not very regular and is extended only a few Angstroms.
  • The amorphous solids are said to possess only short range order.
  • The amorphous solid do not have sharp melting point.
  • This solid do not possess characteristics of heats of fusion.
  • This solid do not give a regular cut when cut with a knife.
  • The amorphous solid can be compressed to some extent.
  • The amorphous solids are isotropic in nature, that is they show the same value of an property in all direction.
  • Amorphous solids are generally regarded as supercooled liquid, because the arrangement of structural units in them is almost similar to that in the liquid.
amorphous solid

Examples – Glass, Wax, Rubber, Starch, Plastics

Difference between Crystalline & Amorphous Solid

PropertiesCrystalline SolidsAmorphous Solids
Arrangement of Structural UnitsVery RegularNot Regular
Geometrical ConfigurationDefiniteNot Definite
Melting PointsVery SharpNot Sharp
Heats of FusionDefinite and characteristicNeither definite nor characteristic
Cleavage with a knifeRegular clean cutIrregular cut
CompressibilityGenerally incompressibleGenerally compressible to some extent
AnisotropyAnisotropic in natureIsotropic in nature

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