Explain why: Rainwater does not leave behind concentric rings when boiled.

Explanation

**Step-by-Step Solution:**

1. **Understanding Rainwater Composition**: Rainwater is primarily composed of pure water and typically does not contain significant amounts of dissolved salts or minerals. This is an important factor in understanding its behavior when boiled.

2. **Boiling Process**: When rainwater is boiled, the heat causes the water to evaporate. In the case of water that contains dissolved salts, the salts do not evaporate with the water. Instead, they remain in the container.

3. **Formation of Concentric Rings**: In water that contains dissolved salts, as the water evaporates, the salts are left behind and can accumulate in specific areas. This accumulation can lead to the formation of concentric rings on the surface of the container due to the uneven distribution of the salts.

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