Which of the following metals expands on solidification?

Which of the following is the composition of glass?

Choose the correct option for crystalline solids based on the following statements:
$(1)$ They do not have a sharp melting point.
$(2)$ They gradually soften upon heating.
$(3)$ They have an irregular three-dimensional arrangement.
$(4)$ They show a rapid change in volume upon heating.

Which of the following dopant is used in silicon to produce $p$-type semiconductor?

Write a note on the classification of materials based on their conductivity.

$A$ clock spring is heated to redness and then plunged into cold water. This treatment will cause it to become