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

Among solids,the highest melting point is established by

Which among the following statements is $NOT$ true about covalent network solids?

Soldiers of Napoleon's army while at the Alps during a freezing winter suffered a serious problem regarding the tin buttons of their uniforms. White metallic tin buttons got converted to grey powder. This transformation is related to

Which of the following characteristic properties is $NOT$ true for crystalline solids?

In $n$-type semiconductors,the conduction of electricity is primarily due to which of the following?