Which term describes a substance\'s gaseous form produced from a liquid or solid at ambient conditions?

• A. Gas
• B. Vapor
• C. Steam
• D. Condensation

Answer: (B)

Vapor is the term for the gaseous form of a substance that is typically a liquid or solid at room temperature. The idea is that the gas arises from evaporation or sublimation of something that isn’t normally a gas under ambient conditions. A familiar example is water: liquid water can evaporate into water vapor even at room temperature. Steam is water vapor produced by boiling water and often includes tiny droplets, so it’s a specific kind of vapor. If a substance is already a gas at ambient conditions, we’d simply call it a gas, not a vapor. Condensation, by contrast, is the process of a vapor turning back into a liquid.