The teacher instructed three students $A$,$B$ and $C$ respectively to prepare a $50\%$ (mass by volume) solution of sodium hydroxide $(NaOH)$. $A$ dissolved $50\,g$ of $NaOH$ in $100\,mL$ of water,$B$ dissolved $50\,g$ of $NaOH$ in $100\,g$ of water while $C$ dissolved $50\,g$ of $NaOH$ in water to make $100\,mL$ of solution. Which one of them has made the desired solution and why?

$A$ child wanted to separate the mixture of dyes constituting a sample of ink. He marked a line by the ink on the filter paper and placed the filter paper in a glass containing water as shown in the figure. The filter paper was removed when the water moved near the top of the filter paper.
$(i)$ What would you expect to see,if the ink contains three different coloured components?
$(ii)$ Name the technique used by the child.
$(iii)$ Suggest one more application of this technique.

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

Which of the following are homogeneous in nature?
$(i)$ ice $(ii)$ wood $(iii)$ soil $(iv)$ air

When is a solution said to be saturated? How can you change an unsaturated solution to a saturated solution without adding any more solute to it?

Which of the following will show the "Tyndall effect"?