$(a)$ State the difference between a pure substance and a mixture. Give one example of each.
$(b)$ Identify homogeneous mixtures from the following:
$(i)$ Smoke
$(ii)$ Brass
$(iii)$ Tincture of iodine
$(iv)$ Milk

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?

$A$ sample of water under study was found to boil at $102\,^{\circ}C$ at normal temperature and pressure. Is the water pure? Will this water freeze at $0\,^{\circ}C$? Comment.

What would you observe when
$(a)$ a saturated solution of potassium chloride prepared at $60\,^{\circ}\text{C}$ is allowed to cool to room temperature.
$(b)$ an aqueous sugar solution is heated to dryness.
$(c)$ a mixture of iron filings and sulphur powder is heated strongly.

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.

Explain the following giving examples:
$(a)$ Saturated solution
$(b)$ Pure substance