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