Why is copper used to make hot water tanks but steel (an alloy of iron) is not used?

Explanation

### Step-by-Step Solution:

1. **Understanding the Materials**:
- Copper and steel (an alloy of iron and carbon) are two different materials with distinct properties.

2. **Reactivity of Iron in Steel**:
- Steel contains iron, which is known to react with water, especially when it is in the form of steam.
- The reaction can be represented as:
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