Give reasons for each of the following:
Natural gas is always found about petroleum deposits inside impervious rocks.

Explanation

**Step-by-Step Solution:**

1. **Understanding Natural Gas and Petroleum**:
- Natural gas and petroleum are both fossil fuels, but they have different physical properties. Natural gas is primarily composed of methane (CH₄) and is lighter than petroleum, which consists of a mixture of hydrocarbons.

2. **Density Comparison**:
- Since natural gas is lighter than petroleum, it tends to rise above it when both substances are present in a geological formation. This is due to the principle of buoyancy, where lighter substances rise above heavier ones.

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