Which term describes the actual amount of water vapor in a mixture of air and water?

Which term describes the actual amount of water vapor in a mixture of air and water?

• A. The weight of water vapor per cubic meter
• B. Absolute humidity
• C. Relative humidity
• D. Vapor pressure

Answer: (B)

What matters here is how much water vapor is actually present in the air. The term that best names that exact quantity is absolute humidity. It is defined as the mass of water vapor per unit volume of air, typically measured in grams per cubic meter. This tells you the real amount of water vapor in the air, independent of how hot or cold the air is. As temperature changes, the air can hold more or less water vapor, so relative humidity (the portion of that capacity that's currently filled) will shift even if the absolute amount stays the same. Vapor pressure refers to the pressure contributed by the water vapor and relates to evaporation tendency rather than the actual mass in the air. Specific humidity describes the mass of water vapor per unit mass of moist air, which is a different way to quantify the moisture content. So for the actual amount of water vapor present, absolute humidity is the most direct and appropriate term.

What matters here is how much water vapor is actually present in the air. The term that best names that exact quantity is absolute humidity. It is defined as the mass of water vapor per unit volume of air, typically measured in grams per cubic meter. This tells you the real amount of water vapor in the air, independent of how hot or cold the air is.

As temperature changes, the air can hold more or less water vapor, so relative humidity (the portion of that capacity that's currently filled) will shift even if the absolute amount stays the same. Vapor pressure refers to the pressure contributed by the water vapor and relates to evaporation tendency rather than the actual mass in the air. Specific humidity describes the mass of water vapor per unit mass of moist air, which is a different way to quantify the moisture content. So for the actual amount of water vapor present, absolute humidity is the most direct and appropriate term.