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

During an experiment, students were asked to prepare a $10\%$ (mass/mass) solution of sugar in water. Ramesh dissolved $10\,g$ of sugar in $100\,g$ of water, while Sarika prepared it by dissolving $10\,g$ of sugar in water to make $100\,g$ of the solution.
$(a)$ Are the two solutions of the same concentration?
$(b)$ Compare the mass percentage of the two solutions.

Identify the dispersed phase and dispersing medium in the following colloids:
$(a)$ Fog
$(b)$ Cheese
$(c)$ Coloured gemstone

Why is the interconversion of states of matter considered a physical change? Give three reasons to justify your answer.

$(a)$ $7\, g$ of iron filings and $4\, g$ of sulphur powder is treated with dilute sulphuric acid at room temperature. Name the gas produced.
$(b)$ The same mixture is heated strongly,cooled and then treated with dilute sulphuric acid. Which gas would be produced?
$(c)$ What is the cause of this difference in results of chemical reaction in different conditions?

$(i)$ 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.