Does all combustible substances give out a flame while burning?

Explanation

**Step-by-Step Solution:**

1. **Understanding Combustible Substances**: Combustible substances are materials that can burn in the presence of oxygen. However, not all of them produce a flame when they burn.

2. **Definition of Flame**: A flame is produced when a substance vaporizes and burns. This vaporization is essential for the formation of a flame.

3. **Examples of Combustible Substances**:
- **LPG (Liquefied Petroleum Gas)**: When LPG burns, it produces a blue flame. This is because LPG is vaporized when it is burned, allowing it to produce a flame.
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