Which of the tubes in Fig. $(a)$ and $(b)$ will be more effective as a condenser in the distillation apparatus?

$A$ 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.

$(i)$ 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.

How can we obtain different gases from air?

How will you separate a mixture of naphthalene powder and common salt? Draw a neat and labelled diagram to show the process.

What is meant by crystallisation? How is impure copper sulphate purified by the process?