Question

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

Answer 1

$\bf{Polyurethane}$ => amorphous solid
$\bf{Naphthalene}$ => crystalline solid
$\bf{Benzoic\:acid}$ => crystalline solid
$\bf{Teflon}$ => amorphous solid
$\bf{Potassium nitrate}$ => crystalline solid
$\bf{Cellophane}$ => amorphous solid
$\bf{Polyvinylchloride}$ => amorphous solid
$\bf{Fibre\:glass}$ => amorphous solid
$\bf{Copper}$ => crystalline solid

amorphous solid :- amorphous solids are not a true solids, they do not have definite heat of fusion , they are isotropic in nature and they are in irregular shape.
crystalline solid :- crystalline solids are true solids, they have definite and characteristics hea of fusion, they are anisotropic in nature and they have definite characteristics geometrical shape.

Answer 2

→ Amorphous Solids : They consist of particles (atoms, ions or molecules) of irregular shape. These have short range order, i.e, regular repeating pattern is observed over short distance only. These are isotropic, do not have sharp melting point, have irregular cleavage.

→ Crystalline Solids : They consist of regular 3D arrangement of atoms, ions or molecules and have well defined geometrical shape. These have long range order. These are anisotropic. They have cleavage property, sharp melting point.

_____________________________

Answer :

Crystalline solids : Benzoic acid, naphthalene, potassium nitrate, copper.

Amorphous solids : Polyurethane, teflon, cellophane, polyvinyl chloride, fibre glass.