Forms of condensation: dew, frost, fog, and mist

Frost forms when the temperature falls to or below freezing and water vapour deposits as tiny ice crystals. These crystals and the freezing conditions can damage tender cells in leaves, buds and flowers, harming crops. Frost does not directly increase soil fertility. Exam tip: associate frost with freezing temperature, ice crystals and crop damage.

Mist has less dense droplets, so visibility is not reduced as much as in fog. Exam tip: treat mist as lighter fog.

Fog is a mass of tiny water droplets suspended in air. Exam tip: connect fog with water droplets.

Dew forms when a surface cools to the dew point and water vapour condenses into tiny liquid water droplets. Frost forms when the temperature is below freezing and water vapour deposits directly as ice crystals. Option A is incorrect because dew is not a gas; it is liquid water. Exam tip: dew means liquid droplets, while frost means ice crystals.

Mist forms when air near the ground cools to its dew point and the water vapour in it condenses into tiny suspended water droplets. These droplets reduce visibility. Fog is a denser form produced by the same process; underground fire, earthquakes, and melting rocks do not cause mist. Exam tip: associate both mist and fog with condensation of water vapour.

At night, surfaces such as grass, leaves, and the ground cool by radiation. When the moist air near them cools to its dew point, water vapour condenses into tiny droplets, which are most noticeable in the morning. In strong afternoon heat, the droplets evaporate. Exam tip: associate dew with cool surfaces after clear, calm nights and with early morning.

Fog is a collection of very tiny water droplets suspended in air near the Earth’s surface. Hence, it is often called a ground-level cloud. A cloud forming high above mountain peaks is not fog. Exam tip: remember fog as a cloud that forms close to the ground.

On a clear calm night the surface can cool enough to form dew. Exam tip: remember clear calm night as a dew condition.

Dew forms when surfaces near the ground cool at night and bring the adjacent air to its dew point. Water vapour then condenses as tiny water droplets on those surfaces, so dew is a surface form of condensation. Frost also forms on surfaces, but it consists of ice crystals formed by direct deposition of water vapour. Fog and mist consist of droplets suspended in the air. Exam tip: droplets on a cool surface indicate dew.

Frost forms when atmospheric water vapour changes directly into tiny ice crystals at very low temperatures. Therefore, water in frost is in the solid state. Dew is different because it forms as liquid water droplets. Exam tip: dew means liquid droplets, while frost means ice crystals.

When moist air cools to dew point, fog can form. Exam tip: connect moist cooling with fog.

Mist is lighter, so seeing distance is greater than in fog. Exam tip: remember mist means better visibility.

In dew, water vapour condenses into liquid droplets. Exam tip: understand dew as liquid condensation.

Frost needs both moisture and a very cold surface. Exam tip: remember moisture plus freezing surface for frost.

In fog, water vapour changes into tiny droplets. Exam tip: treat fog as a condensation process.

Fog reduces seeing distance because of tiny droplets in air. Exam tip: remember fog impact as low visibility.

Grass and leaves can cool quickly at night. Exam tip: connect cool surfaces with dew formation.

The icy solid form on a cold surface is called frost. Exam tip: identify icy deposit as frost.

Mist is seen when very tiny water droplets remain suspended in the air. These droplets scatter light and reduce visibility. Completely dry air does not have enough moisture for condensation. Exam tip: remember mist as a light form of fog near the ground.

Dew point is the temperature where air can become saturated. Exam tip: connect dew point with condensation.