What happens when calcium is treated with water? (i) It does not react with water. (ii) It reacts violently with water. (iii) It reacts less violently with water. (iv) Bubbles of hydrogen gas formed stick to the surface of calcium.

Calcium reacts with cold water, but the reaction is less violent than that of sodium or potassium. It forms calcium hydroxide and hydrogen gas: Ca + 2H2O → Ca(OH)2 + H2↑. During the reaction, bubbles of hydrogen gas formed stick to the surface of calcium. As a result, calcium starts floating on the surface of water. Therefore, statement (iii) is correct because calcium reacts less violently with water, and statement (iv) is also correct because hydrogen bubbles adhere to its surface. Thus, statements (iii) and (iv) are correct.