Which metal does not react with water ?

Options

A. Na
B. Mg
C. Cu
D. Fe

Explanation

To determine which metal does not react with water, we will analyze the reactivity of each of the given options: sodium, magnesium, copper, and iron.

### Step-by-Step Solution:

1. **Identify the Metals**: The metals given in the options are:
- A) Sodium (Na)
- B) Magnesium (Mg)
- C) Copper (Cu)
- D) Iron (Fe)

2. **Check Reactivity of Sodium**:
- Sodium reacts vigorously with cold water. The reaction can be represented as:
\[ \text{Na} + \text{H}_2\text{O} \rightarrow \text{NaOH} + \frac{1}{2}\text{H}_2 \]
- Since sodium reacts with water, it is not the correct answer.

3. **Check Reactivity of Magnesium**:
- Magnesium reacts with warm water but does not react with cold water. The reaction with warm water is:
\[ \text{Mg} + 2\text{H}_2\text{O} \rightarrow \text{Mg(OH)}_2 + \text{H}_2 \]
- Since magnesium does react with water (even if only warm), it is also not the correct answer.

4. **Check Reactivity of Copper**:
- Copper does not react with cold, warm, or steam forms of water. The reaction can be summarized as:
\[ \text{Cu} + \text{H}_2\text{O} \rightarrow \text{No Reaction} \]
- Since copper does not react with water, it is a potential correct answer.

5. **Check Reactivity of Iron**:
- Iron reacts with boiling water (steam). The reaction can be represented as:
\[ 3\text{Fe} + 4\text{H}_2\text{O} \rightarrow \text{Fe}_3\text{O}_4 + 4\text{H}_2 \]
- Since iron does react with water (specifically steam), it is not the correct answer.

6. **Conclusion**:
- The only metal that does not react with water is **Copper (Cu)**.

### Final Answer:
**Copper (Cu) does not react with water.**