A ____ is produced only by those substances that vaporize on heating.

Options

A. Combustion
B. Flame
C. Heating
D. Burning

Answer

To solve the question "A ____ is produced only by those substances that vaporize on heating," we need to identify the term that fits the description provided.

### Step-by-Step Solution:

1. **Understanding the Question**: The question states that a certain phenomenon occurs only when substances vaporize upon heating. This indicates that we are looking for a specific result of this vaporization.

**Hint**: Think about what happens when a substance is heated and turns into a gas.

2. **Identifying the Process**: When a substance vaporizes, it typically undergoes a phase change from liquid to gas. This process is often associated with the release of energy in the form of heat and light.

**Hint**: Consider what is produced when a gas is formed from a heated liquid.

3. **Connecting to Combustion**: Substances that vaporize can often be combustible, meaning they can react with oxygen to produce heat and light. This reaction is known as combustion.

**Hint**: Recall what happens during combustion and what is produced as a result.

4. **Determining the Correct Term**: The term that describes what is produced when a substance vaporizes and then burns is "flame." A flame is the visible, gaseous part of a fire, which is produced by the combustion of vaporized substances.

**Hint**: Think about examples of substances that produce flames when heated.

5. **Final Answer**: Therefore, the correct answer to fill in the blank is "flame."

### Final Answer:
A **flame** is produced only by those substances that vaporize on heating.

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