Give reasons: $Sodium$,$potassium$,and $lithium$ are stored under oil.

What would you observe when zinc is added to a solution of iron $(II)$ sulphate? Write the chemical reaction that takes place.

Give an example of a metal which:
$(i)$ is a liquid at room temperature.
$(ii)$ can be easily cut with a knife.
$(iii)$ is the best conductor of heat.
$(iv)$ is a poor conductor of heat.

Samples of four metals $A$,$B$,$C$ and $D$ were taken and added to the following solutions one by one. The results obtained have been tabulated as follows.

Metal	Iron $(II)$ sulphate	Copper $(II)$ sulphate	Zinc sulphate	Silver nitrate
$A$	No reaction	Displacement	No reaction	Displacement
$B$	Displacement	Displacement	No reaction	Displacement
$C$	No reaction	No reaction	No reaction	Displacement
$D$	No reaction	No reaction	No reaction	No reaction

Use the table above to answer the following questions about metals $A$,$B$,$C$ and $D$:
$(i)$ Which is the most reactive metal?
$(ii)$ What would you observe if $B$ is added to a solution of Copper $(II)$ sulphate?
$(iii)$ Arrange the metals $A$,$B$,$C$ and $D$ in the order of decreasing reactivity.

What are alloys?

Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).