Certified Fire Investigator Practice Exam

What is the definition of vapor?

1. The liquid phase of a substance

2. The gas phase of a substance

3. A solid state of a substance

4. A mist created by a substance

The correct answer is: The gas phase of a substance

The definition of vapor refers specifically to the gas phase of a substance when it is in a state that is typically a liquid or solid at standard conditions. This transition from liquid or solid to gas occurs through processes such as evaporation or sublimation. Vapor is distinct from the liquid phase, which is when the substance remains in its liquid form. It is also different from the solid state, which describes a substance that retains a fixed shape and volume. Additionally, while a mist can be formed when tiny droplets of liquid are suspended in the air, it does not accurately represent the gas phase of the substance. Therefore, defining vapor as the gas phase of a substance is the only definition that correctly captures its scientific meaning.