Crystallisation is a better technique than simple evaporation. Give one reason to justify the statement.

$A$ 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.

Which of the following statements are true for pure substances?
$(i)$ Pure substances contain only one kind of particles.
$(ii)$ Pure substances may be compounds or mixtures.
$(iii)$ Pure substances have the same composition throughout.
$(iv)$ Pure substances can be exemplified by all elements other than nickel.

$(i)$ 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 is a compound?

Colloidal solution appears to be homogeneous but actually it is heterogeneous. Give justification for this statement.