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

Rusting of an article made of iron is called:

How are mixtures different from compounds?

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

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?

Which of the following will show Tyndall effect? Why?
$(a)$ Salt solution
$(b)$ Milk
$(c)$ Copper sulphate solution
$(d)$ Starch solution.