How does vapor convert into the water?

The condensation process entails water vapor in the atmosphere getting converted into water droplets or ice and hence releasing the latent heat locked within them back into the atmosphere.

Condensation

The process of Condensation is basically the reverse of Evaporation. The process of transformation of water vapor (gas) into water (liquid) and ice (solid) is termed condensation. Condensation can only occur when water vapor is added to saturated air or when the temperature falls below the temperature at which the air becomes saturated.

Basically, Condensation begins when the saturated air mass reaches the dew point. Dew point is the level at which the air is not in a position to take up any more moisture. For example at 25 degrees Celcius temperature, air can hold 30 gm of water vapor per cubic meter. Now if the temperature falls to 20 degrees Celcius, it can hold only 24 gm of water vapor. The remaining 6 gm of water vapor will get condensed.

In the atmosphere, the nuclei for the condensation of moisture are provided by smoke and dust particles. Condensation can occur in one of the following ways:

1. When the warm, moist air rises upwards and expands.
2. When the warm moist air comes in contact with the cold surface.
3. When the warm moist air mixes with the air coming from the colder regions.

Once the condensation of water vapor in the atmosphere has taken place, the moisture in the atmosphere may take forms such as dew, frost, fog, mist, clouds, etc., according to the conditions prevalent in the atmosphere.

Dew and Frost

When the relative humidity of the air is low, even a drop in temperature during winter nights fails to saturate the air.

Hence condensation does not take place in the air, but it occurs on some solid surfaces like leaves, flowers, grass-blades, pieces of rocks, etc., which becomes cool due to quick radiation at night. Air in contact may get chilled to dew point and condensation takes place. The deposition of water droplets on these objects is called dew.

Sometimes a surface may cool through loss of infrared radiation to a temperature that is colder than the dew point of the air next to the surface and hence, solid objects become so cold that in place of water droplets, minute crystals of ice gets deposited on these solid objects. This is called frost. Frost is very harmful to plants and can destroy standing crops.

Fog and Mist

Fog is a visible aerosol consisting of very small water droplets which remain suspended in the air close to Earth's surface. During the winter months, excessive radiation at night results in the fall of air temperature. If the fall relative humidity is very high, the fall in temperature causes condensation of moisture in the air resting on the Earth's surface.

The condensation of water vapor takes place around the dust and smoke particles that remain suspended in the air. It is called fog. Mist is nothing but a light fog. According to meteorological practice, such a phenomenon is mist when the visibility is between 1000 meters to 2000 meters and becomes a fog when the visibility falls below 1000 meters.

Questions

1. Which of them is very harmful to plants and can destroy the standing crops?
(i) Fog
(ii) Mist
(iii) Dew
(iv) Frost

2. The deposition of water droplets on objects like flowers, grass blades, leaves, etc. is called
(i) Fog
(ii) Frost
(iii) Mist
(iv) Dew

3. The level at which the air is not in a position to take up any more moisture is called
(i) Saturation point
(ii) Absolute point
(iii) Freezing point
(iv) Dew point

4. In nature, what provides the nuclei for the condensation of moisture?
(i) Water vapor
(ii) Oxygen
(iii) Carbon dioxide
(iv) Smoke and dust particles

5. What is the phenomenon called, in which the visibility is between 1000 meters to 2000 meters?
(i) Fog
(ii) Frost
(iii) Smog
(iv) Mist

Read More: What is Precipitation: Process, Condition Necessary, and Distribution - Class 9