What happens when calcium reacts with water?

Calcium is a reactive metal that belongs to Group 2 (alkaline earth metals) of the periodic table. When calcium is added to water, it reacts slowly and forms calcium hydroxide and hydrogen gas.

The chemical equation for this reaction is:

Ca (s) + 2H₂O (l) → Ca(OH)₂ (aq) + H₂ (g)

In this reaction, calcium (Ca) reacts with water (H₂O) to form calcium hydroxide [Ca(OH)₂], which is a slightly soluble base, and hydrogen gas (H₂) is released. You may observe bubbles forming on the surface of calcium due to the release of hydrogen gas.

Observation and Explanation

• When calcium is added to water, it sinks because it is denser than water.
• A mild effervescence is observed as hydrogen gas is slowly released.
• The solution becomes slightly milky due to the formation of calcium hydroxide, which is only slightly soluble in water and forms a suspension.
• The resulting solution is basic in nature and turns red litmus paper blue, indicating its alkalinity.

This reaction is less vigorous than the reaction of alkali metals like sodium and potassium with water. While sodium and potassium react explosively, calcium reacts much more calmly.

Also, the heat produced during the reaction is not enough to ignite the hydrogen gas, which is why flames or explosions are not observed, unlike in the case of sodium or potassium.

Safety Note

Though the reaction is not very violent, it should still be handled carefully in a controlled environment, such as a laboratory, under the supervision of a teacher.

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