(i) The sun’s heat vaporises water into vapour. This vapour cools down and condenses to become clouds. This may then fall on the surface of Earth in the form of rain, snow or sleet. This phenomenon of water falling back onto the surface of the earth in the form of rain, snow or sleet is called precipitation.
(ii) The process by which water continually changes its form and circulates between oceans, atmosphere and land is known as the water cycle.
(iii) The factors affecting the height of the waves are as follows:
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Speed of the wind
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Earthquake, volcanic eruptions or underwater landslides
(iv) The factors affecting the movement of ocean water are as follows:
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Temperature
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The gravitational pull of sun and moon
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Warm and cold currents
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Wind
(v) The rhythmic rise and fall of ocean water, twice in a day, is called a tide. Tides are caused by the gravitational force exerted by the sun and the moon on the earth’s surface.
(vi) The streams of water flowing constantly on the ocean surface in a definite direction are called ocean currents. The ocean currents may be warm or cold.