- Water is found in the all three states of matter in everyday life. It is found in the solid state as ice form, in the liquid state as water and in the gaseous state as water vapour.
- Different forms of water influence the earth and the living beings.
- Water is found in glaciers, oceans, rivers and streams and in the form of water vapour.
- Global water balance is maintained by the flow of the water in and out of the system.
- Major inflow in the system is through precipitation and the outflow is through evapo-transpiration. It is also referred as water or hydrological cycle. The interchange of the different states of water between the ocean, land and air is called hydrological cycle.
- Physical processes of water cycle are evaporation, precipitation and condensation.
- Evaporation is the process by which water is transformed into the water vapours by the sun’s heat. The factors affecting evaporation are temperature, dry air, clear sky and winds.
- When the air is holding maximum amount of water it can hold, the air is said to be saturated. The temperature at which the air gets saturated is known as dew point.
- Condensation is the process by which water vapour is converted into water. The various forms of condensation are cloud, mist, fog, dew and frost.
- Precipitation is the process through which water from the atmosphere falls down on the earth. The various forms of precipitation are rain, drizzle, snow, sleet and hail.
- In evaporation, water changes into water vapour. In condensation, water vapour changes into the water. In precipitation, water falls down on the earth’s surface.
- Heat is absorbed in the process of evaporation. Heat is released in the process of condensation. No absorption or release takes place in the process of precipitation.
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What is the movement of ocean water?Marks:1
The movements that occur in oceans can be broadly categorised as waves, tides, and currents.
What percentage of Earth's water is in the oceans?Marks:1
Oceans contain about 97.3% of the earth's water while the remaining are classified as freshwater.
What is the amount of salt present in 1000 grams of water known?Marks:1
Salinity is the amount of salt in grams present in 1000 grams of water. The average ocean salinity is 35 ppt. This number varies from 32 to 37 ppt. Rainfall, evaporation, river runoff, and ice formation causes the variations. For example, the Black Sea is so diluted by river runoff; its average salinity is only 16 ppt.
A major source of fresh water isMarks:1
Oceans contain about 97% of the earth's water while the remaining 3% is classified as freshwater. 77% of this surface freshwater is stored as ice and 22% as groundwater and soil moisture. The remaining freshwater, making up less than 1% of the world's total, is contained in lakes, rivers, and wetlands.
Ocean water isMarks:1
As water flows in rivers, it picks up small amounts of mineral salts from the rocks and soil of the river beds. This very-slightly salty water flows into the oceans and seas. Water from the oceans evaporate, but the salt remains in it. So, the remaining water gets saltier and saltier as time passes.