7. Which of the following materials fall into the category of pure substances?
(a) Ice, (b) milk,
(c) iron, (d) hydrochloric acid,
(e) calcium oxide, (f) mercury,
(g) brick, (h) wood,
(i) air
7. Which of the following materials fall into the category of pure substances?
(a) Ice, (b) milk,
(c) iron, (d) hydrochloric acid,
(e) calcium oxide, (f) mercury,
(g) brick, (h) wood,
(i) air