Part-1. Properties of crystalline solids | M.pt & B.pt, Cleavage and anisotropy | ch#4 | 11th class

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I have discussed about the properties of crystalline solids in 11th class Chemistry, punjab text book chemistry.
Properties of Crystalline Solids
1. Geometrical Shape
All the crystalline solids have a deinite, distinctive geometrical shape due to deinite and
orderly arrangement of atoms, ions or molecules in three-dimensional space. For a given crystal,
the interfacial angles, at which the surfaces intersect, are always the same no matter in which shape
they are grown. The faces and angles remain characteristic even when the material is ground to a ine powder.
2. Melting Points
Crystalline solids have sharp melting points and can be identiied from their deinite melting
points.
3. Cleavage Planes
Whenever the crystalline solids are broken they do so along deinite planes. These planes
are called the cleavage planes and they are inclined to one another at a particular angle for a given
crystalline solid. The value of this angle varies from one solid to another solid.
Anisotropy
Some of the crystals show variation in physical properties depending upon the
direction. Such properties are called anisotropic properties and the phenomenon is referred
to as anisotropy. The physical properties of crystalline solids like refractive index, coeicient of
thermal expansion, electrical and thermal conductivities are sometimes anisotropic in nature for some crystals.