In an experiment, a safety pin is placed on a sheet of paper and the sheet is held over a burning candle until it is yellow and charred. On removing the pin, its white trace is seen on the paper. Explain the observation with reasoning.

Explanation

To explain the observation of a white trace left by the safety pin on a charred sheet of paper, we can break down the reasoning into a step-by-step solution.

### Step-by-Step Solution:

1. **Setup of the Experiment**:
- A safety pin is placed on a white sheet of paper.
- The paper is held over a burning candle until it becomes yellow and charred.

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