Give an example of a very slow combustion.

Explanation

### Step-by-Step Solution:

1. **Understanding Slow Combustion**: Slow combustion is a type of combustion that occurs at a very slow rate and releases very little heat. It often involves the gradual reaction of a substance with oxygen over time.

2. **Identifying an Example**: One common example of very slow combustion is the rusting of iron. This process occurs when iron reacts with oxygen in the presence of moisture over an extended period.

3. **Describing the Reaction**: The chemical reaction for the rusting of iron can be represented as follows:
- Iron (Fe) reacts with oxygen (O2) and water (H2O) to form iron(III) oxide hydrate, commonly known as rust (Fe2O3·2H2O).
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