How can you convert a saturated solution into an unsaturated solution?

When is a compound said to be pure?

Classify the following as physical or chemical properties:
$(a)$ The composition of a sample of steel is: $98\%$ iron,$1.5\%$ carbon,and $0.5\%$ other elements.
$(b)$ Zinc dissolves in hydrochloric acid with the evolution of hydrogen gas.
$(c)$ Metallic sodium is soft enough to be cut with a knife.
$(d)$ Most metal oxides form alkalis on interacting with water.

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

The 'sea-water' can be classified as a homogeneous as well as heterogeneous mixture. Comment.

Classify each of the following as an element,compound,or mixture:
Gold,Air,Marble,Milk,Sugar.