The temperature at which the water vapor in the air saturates the air and begins to condense is known as

Step 1: Analyze the question The question asks for the temperature at which air becomes saturated with water vapor and the vapor starts to condense into liquid water (like the droplets on a cold bottle of "Coke" or morning dew on grass).

Step 2: Explain the concept Air can hold only a certain amount of water vapor at a given temperature. Cooler air holds less. If air is cooled enough, it reaches a temperature where it is fully saturated (100% relative humidity). Cooling it further makes the vapor condense into liquid droplets. This temperature is called the dew point.

Step 3: Check each option

• A. Dew point: The temperature at which air becomes saturated and water vapor begins to condense. This matches the question.
• B. Critical point: The temperature and pressure above which a gas cannot be liquefied by pressure alone. It has nothing to do with air humidity.
• C. Boiling point: The temperature at which a liquid's saturated vapor pressure equals the external pressure, so the liquid boils.
• D. Triple point: The unique temperature and pressure at which solid, liquid, and gas phases of a substance coexist in equilibrium (for water, 0.01 °C).

Step 4: Answer The correct option is A. dew point.

Exam tip: Remember "Dew forms at the Dew point." Whenever you see condensation, saturation, humidity, or fog, think dew point. Also remember that relative humidity is 100% at the dew point, and that hygrometers are used to find it.