Which of the following is a compound?

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

$(i)$ Name the process or the separation technique you would follow to separate:
$(a)$ Dyes in black ink
$(b)$ Butter from cream
$(c)$ Ammonium chloride and common salt
$(d)$ Iron filings and sand
$(ii)$ State the principle used in separation by centrifugation.

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

$(a)$ Both smoke and fog are aerosols. In what way are they different?
$(b)$ How do sol and gel differ from each other? Give one example for each.

$(a)$ Illustrate with an example that physical and chemical changes can take place together.
$(b)$ Which of the following are chemical changes?
$(i)$ Mixing of iron filings and sand
$(ii)$ Growth of plant
$(iii)$ Rusting of iron
$(iv)$ Freezing of water