Explain anisotropy in crystalline solids.

(A): Crystalline solids are anisotropic (R): Crystalline solids are not as closely packed as amorphous solids.

Mention various types of ·crystalline solids. Give examples.

Example of crystalline solid .

(A) Crystalline solids can cause X-rays to diffract. (R) lnteratomic distance in crystalline solids is of the order of 0.1 nm.

Mention four important porperties of crystalline solids.

An X-ray beam (lambda = 70.9 p m) was scattered by a crystalline solid. The angle (2theta) of the diffraction for a second order reflection is 14.66^(0) . Calculate the distance between parallel planes of atoms of the crystalline solid.

Classify the following as amorphous or crystalline solids : polyurethane , naphthalene , benzoic acid , teflon , potassium nitrate , cellophane , polyvinyl chloride , fibre glass , copper .