How can you convert a saturated solution into an unsaturated solution?

Suggest separation technique$(s)$ one would need to employ to separate the following mixtures:
$(a)$ Mercury and water
$(b)$ Potassium chloride and ammonium chloride
$(c)$ Common salt,water and sand
$(d)$ Kerosene oil,water and salt

How is heating of sugar and heating of ammonium chloride different from each other? Explain your answer.

$A$ solution contains $50 \, g$ of sugar in $350 \, g$ of water. Calculate the concentration of the solution in terms of mass by mass percentage of the solution. (in $\%$)

How is a pure substance different from a mixture?

Why is the interconversion of states of matter considered a physical change? Give three reasons to justify your answer.