Sodium cannot be preserved in water. However, sodium amalgan can be kept in water. Justify.

Explanation

### Step-by-Step Solution:

1. **Understanding Sodium's Reactivity**: Sodium is a highly reactive alkali metal. When it comes into contact with water, it reacts vigorously to form sodium hydroxide and hydrogen gas. This reaction is exothermic, meaning it releases a significant amount of heat.

2. **Reaction of Sodium with Water**: The chemical reaction can be represented as:
\[ 2 \text{Na} + 2 \text{H}_2\text{O} \rightarrow 2 \text{NaOH} + \text{H}_2 \uparrow \]
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