Humidity, evaporation, and condensation

Dew forms when water vapour condenses on a cool surface. Exam tip: understand dew as condensation near the ground.

Clouds form when water vapour condenses into water droplets or ice particles. Exam tip: remember cooling air in cloud formation.

Absolute humidity tells the actual water vapour present in air. Exam tip: remember it as the actual amount type.

More water vapour means higher humidity. Exam tip: remember the direct relation between water vapour and humidity.

Dry air contains very little water vapour, so its humidity is low. Fully saturated air, in contrast, holds the maximum possible water vapour at a given temperature and cannot be called dry. Exam tip: associate dry air with low humidity and low water-vapour content.

High temperature helps water change into vapour faster. Exam tip: remember heat as a factor that increases evaporation.

Condensation becomes more likely when air cools. Exam tip: connect condensation with falling temperature.

After evaporation, water vapour cools and condenses. Exam tip: remember the water cycle sequence from evaporation to condensation.

A barometer measures atmospheric pressure, or air pressure. Relative humidity is measured with a hygrometer, while rainfall is measured with a rain gauge. Exam tip: learn instrument-measurement pairs, such as barometer–air pressure and hygrometer–humidity.

In high humidity, sweat evaporates slowly. Exam tip: understand the link between moisture and discomfort.

More humid air has less capacity to take more water vapour. Exam tip: link high humidity with lower evaporation.

Large water surfaces of seas and oceans cause much evaporation. Exam tip: remember oceans as a major moisture source.

Cool grass helps water vapour change into water droplets. Exam tip: remember a cool surface as the cause of dew formation.

Water vapour is water in its gaseous state and is present invisibly in the atmosphere. Liquid water may form tiny droplets in clouds, fog or dew, but water vapour itself is a gas. Exam tip: associate the word “vapour” with the gaseous state of water.

In evaporation, liquid water becomes gaseous water vapour. Exam tip: remember the state change clearly.

In condensation, water vapour changes into liquid droplets. Exam tip: remember condensation as cooling of vapour.

High relative humidity indicates air is near saturation. Exam tip: link high humidity with the possibility of rainfall.

Water vapour is necessary for clouds and rainfall. Exam tip: treat water vapour as the basic material for rain.

When air cools, its saturation water-vapour holding capacity decreases. Thus, cooling air can reach saturation more easily, and further cooling may lead to condensation. ‘It remains unchanged’ is incorrect because this capacity varies with temperature. Exam tip: lower temperature means lower water-vapour capacity.

Dry and moving air speeds up evaporation. Exam tip: treat drying of sweat as a daily example of evaporation.