Arun has prepared a $0.01\%$ (by mass) solution of sodium chloride in water. Which of the following correctly represents the composition of the solution?

Which of the two will scatter light: soap solution or salt solution?

$A$ group of students took an old shoe box and covered it with black paper from all sides. They fixed a source of light (a torch) at one end of the box by making a hole in it and made another hole on the other side to view the light. They placed a milk sample contained in a beaker/tumbler in the box as shown in the figure. They were amazed to see that the milk taken in the tumbler was illuminated. They tried the same activity by taking a salt solution but found that light simply passed through it.
$(a)$ Explain why the milk sample was illuminated. Name the phenomenon involved.
$(b)$ Same results were not observed with a salt solution. Explain.
$(c)$ Can you suggest two more solutions which would show the same effect as shown by the milk solution?

Describe any three properties of colloids. Categorise the following examples of colloids into different categories of colloids: Jelly,fog,milk,shaving cream.

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.

Which of the following are homogeneous in nature?
$(i)$ ice $(ii)$ wood $(iii)$ soil $(iv)$ air