Question

Which of the following materials fall in the category of a “pure substance”?

(a) Ice
(b) Milk
(c) Iron
(d) Calcium oxide
(e) Mercury
(f) Brick
(g) Wood
(h) Air

Answer 1

Pure substances are substances which consist of a single type of particles. Pure substances have constant composition and have constant properties throughout the samples.

Among the given options: Ice, iron, calcium oxide and mercury are classified as pure substances, where ice and calcium oxide are compounds and mercury is an element.

Milk, wood, brick and air are constituted by physical combination of two or more substances having variable composition. Hence these are classified as mixtures.