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

Fill in the blanks:
$(a)$ $A$ colloid is a .......... mixture and its components can be separated by the technique known as .........
$(b)$ Ice,water,and water vapour look different and display different ......... properties but they are ......... the same.
$(c)$ $A$ mixture of chloroform and water taken in a separating funnel is mixed and left undisturbed for some time. The upper layer in the separating funnel will be of ......... and the lower layer will be that of .........
$(d)$ $A$ mixture of two or more miscible liquids,for which the difference in the boiling points is less than $25 \, K$,can be separated by the process called .........
$(e)$ When light is passed through water containing a few drops of milk,it shows a bluish tinge. This is due to the ......... of light by milk and the phenomenon is called ......... . This indicates that milk is a ......... solution.

State any one difference between pure and impure substances.

Explain why particles of a colloidal solution do not settle down when left undisturbed,while in the case of a suspension they do.

Iron filings and sulphur were mixed together and divided into two parts,$A$ and $B$. Part $A$ was heated strongly while Part $B$ was not heated. Dilute hydrochloric acid was added to both the parts and evolution of gas was seen in both the cases. How will you identify the gases evolved?

What is the effect of temperature on the solubility of solids in liquids?