In a crystal,the atoms are located at the position of

Classify the following materials into superconductors,conductors,semiconductors,and insulators: $Cu$,$Al$,$Si$,$Ge$,glass,Teflon,$Au$,$Pt$,$CuO$ (at low temperature),graphite,carbon black,and alloys at low temperature.

What type of substances would make better permanent magnets,ferromagnetic or ferrimagnetic? Justify your answer.

Identify the incorrect set from the following:

The value of the heat of fusion of $NaCl$ is:

What is the main use of $Quartz$?