Humidity, evaporation, and condensation

Evaporation occurs from the surface of water in an open container. Exam tip: remember open water as a simple example of evaporation.

Humidity represents the amount of water vapour present in air. Exam tip: always connect humidity with moisture in air.

The change of liquid water into vapour is called evaporation. In exams connect it with heat and open surface.

When water vapour cools and changes into droplets it is called condensation. In exams treat clouds and dew as examples of condensation.

Warm air can hold more water vapour. For exams remember that air moisture holding capacity increases with temperature.

Relative humidity compares present water vapour with the maximum capacity of air. For exams remember it is expressed as a percentage.

A hygrometer measures humidity of air. For exams keep hygrometer for humidity and rain gauge for rainfall separate.

High temperature and dry air make evaporation faster. For exams remember heat and low humidity favour evaporation.

Wind increases evaporation by removing moist air near the surface. For exams connect wind with faster drying of clothes.

Air is called saturated when it holds water vapour up to its capacity. For exams connect saturated air with maximum water vapour.

At night water vapour condenses on a cooled surface and forms dew. For exams treat dew as condensation on a surface.

At height water vapour condenses in cool air to form clouds. For exams connect cloud formation with cooling and condensation.

Oceans are the largest source of water on Earth so they contribute greatly to evaporation. For exams remember oceans as the main moisture source of the water cycle.

Evaporation needs heat so the surface feels cooler. For exams use sweating and cooling as a simple example.

In high humidity air is already moist so evaporation becomes slow. For exams remember clothes dry slowly on humid days.

When water vapour cools it changes into droplets. For exams remember cooling as the main cause of condensation.

Fog forms by condensation as tiny droplets near the ground. For exams think of fog as a cloud near the surface.

Absolute humidity gives the actual amount of water vapour present in air. For exams identify it by actual water vapour amount.

Specific humidity is related to the amount of water vapour in a mass of air. For exams remember it with mass of air.

Dew point is the temperature at which air becomes saturated and condensation may start. For exams treat dew point as saturation temperature.