The substances that sublime easily are

Three students $A, B$ and $C$ prepared mixtures using chalk powder,common salt and milk respectively in water. Whose mixture
$(i)$ would not leave residue on filter paper after filtration?
$(ii)$ would show Tyndall effect?
$(iii)$ would give transparent/clear solution?
$(iv)$ would settle down at the bottom when left undisturbed?
$(v)$ could be filtered by filter paper?

Why does a mixture not have a fixed melting or a fixed boiling point?

Sucrose (sugar) crystals obtained from sugarcane and beetroot are mixed together. Will it be a pure substance or a mixture? Give reasons for the same.

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.

Explain why particles of a colloidal solution do not settle down when left undisturbed,while in the case of a suspension they do.