Correct Option
The correct option is Hydrogen bubbles adhere to its surface.
Explanation
The reaction of calcium with water is a characteristic chemical property of alkaline earth metals. While calcium is denser than water, its interaction with water produces specific physical observations due to the nature of the products formed.
Detailed Analysis
When calcium reacts with water, it forms calcium hydroxide and releases hydrogen gas according to the following equation:
Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g)
- The reaction is exothermic but less violent compared to alkali metals like sodium or potassium. The heat evolved is not sufficient for the hydrogen to catch fire.
- As the reaction proceeds, bubbles of hydrogen gas are produced.
- These gas bubbles adhere to the surface of the calcium metal.
- The buoyancy provided by the attached hydrogen bubbles counteracts the density of the metal, causing the calcium to float on the surface of the water.
Key Takeaway: Calcium floats on water during the reaction because bubbles of hydrogen gas formed stick to the metal surface, providing the necessary buoyancy.