Calcium reacts slowly but noticeably with water, unlike its neighbor magnesium which is much less reactive with cold water. The reaction is exothermic, meaning it releases heat.
The Reaction
The reaction between calcium and water produces two products:
- Calcium hydroxide (Ca(OH)₂): This forms a cloudy, milky white precipitate in the water, as it's only slightly soluble.
- Hydrogen gas (H₂): This is released as bubbles and can be ignited, producing a small flame. As noted in one YouTube demonstration Reaction between Calcium and Water - YouTube, the hydrogen gas produced can be observed burning.
The balanced chemical equation for this reaction is:
Ca(s) + 2H₂O(l) → Ca(OH)₂(aq) + H₂(g)
Reaction Speed and Temperature
The reaction speed is influenced by temperature. While calcium reacts with cold water, it reacts more vigorously with hot water. Does calcium react with hot water? - Quora This is a common characteristic of many chemical reactions; higher temperatures increase the rate of reaction.
Practical Observations
Several sources describe observable changes during the reaction:
- The water becomes cloudy due to the formation of the slightly soluble calcium hydroxide.
- Bubbles of hydrogen gas are visibly released.
- Heat is generated, making the water slightly warmer.
A YouTube video demonstrates this reaction visually. Reaction between Calcium and Water - YouTube Calcium Reacts with Water - YouTube
