Theory:

Water Cycle
What is the water cycle?
The constant movement of water from the earth to the atmosphere as water vapour and back again to the earth in the form of rain is known as the water cycle.
The sun and the water bodies such as the oceans, seas, rivers and lakes are the components of the water cycle.
What happens during this cycle?
During the day time a portion of the earth's surface gets heated up due to the heat produced by the sun.
 
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The water here evaporates into the atmosphere as water vapor. Later it cools down as returns back to the earth in the form of rain that later on forms rivers, streams and underground water.
The water that again returns back to the earth does not have any salts with it and hence can be used in daily life. This is because when the saltwater vaporizes, it loses its salinity.
Processes involved in water cycle
The three major processes that are involved in the water cycle are evaporation, transpiration and condensation.
  
1. Evaporation:
 
The process in which the water converts into water vapour due to heating is known as evaporation.
It is process through which the saline water vaporizes and reaches the atmosphere after losing its salts.
  
2. Transpiration:
  
Plants use water for the preparation of their food during photosynthesis.
The release of the remaining water into the air by the plants is known as transpiration.
Important!
The water vapour enters the atmosphere by the processes of evaporation and transpiration.
3. Condensation:
The process by which a vapour becomes a liquid by cooling down is known as condensation.
This is the process through which the water returns back to the earth in the form of rain, snow or hail. The water vapor cools down and forms water droplets that come closer together and form clouds.
 
4. Precipitation:
 
When the size of these droplets increase they fall on the earth as rainfall. This is known as precipitation.
Important!
The water that is lost from the earth returns back to the earth through the process of the water cycle.