What is the effect of temperature on the solubility of solids in liquids?

What is meant by concentration of a solution?

How can we separate a mixture of two immiscible liquids?

What would you observe when:
$(a)$ a saturated solution of potassium chloride prepared at $60^{\circ} C$ is allowed to cool at room temperature?
$(b)$ an aqueous sugar solution is heated to dryness?
$(c)$ a mixture of iron filings and sulphur powder is heated strongly?

Why does a copper sulphate solution in water not show the Tyndall effect,while a mixture of water and milk does?

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?