State whether the following statement is true or false:
$A$ compound is a substance composed of two or more elements,chemically combined with one another in a fixed proportion.

Smoke and fog both are aerosols. In what way are they different?

Calculate the mass of sodium sulphate required to prepare its $20\%$ (mass percent) solution in $100\,g$ of water. (in $,g$)

You are given two samples of water labelled as $A$ and $B$. Sample $A$ boils at $100\,^{\circ}C$ and sample $B$ boils at $102\,^{\circ}C$. Which sample of water will not freeze at $0\,^{\circ}C$? Comment.

Give an example each of a mixture that shows the following characteristics:
$(i)$ $A$ mixture of two coloured components.
$(ii)$ $A$ mixture of two volatile components with a boiling point difference of less than $25\ K$.
$(iii)$ $A$ mixture of a volatile and a non-volatile solid component.

You are provided with a solution of substance $'X'$. How will you test whether it is saturated or unsaturated with respect to $'X'$ at a given temperature? What happens when a hot saturated solution is allowed to cool?