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.

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(i) and (iv)

(ii) and (iii)

(i) and (ii)

(iii) and (iv)

answer is D.

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Detailed Solution

When calcium is treated with water:

Calcium reacts less violently with water compared to highly reactive metals like sodium or potassium. This rules out option (ii).
Calcium produces hydrogen gas, which forms bubbles on its surface. These bubbles stick to the surface of calcium, causing hydrogen to float. This confirms option (iv).
The reaction produces calcium hydroxide, which slightly dissolves in water to make the solution alkaline.

Hence, the correct answers are (iii) It reacts less violently with water and (iv) Bubbles of hydrogen gas formed stick to the surface of calcium.

Key Concept:

What happens when calcium is treated with water is that it reacts moderately, forming hydrogen gas and calcium hydroxide. Unlike more reactive metals, this reaction is not violent but steady. The hydrogen gas produced adheres to calcium, making it appear as though bubbles are sticking to the surface.