Introduction About Water An Essential Resource:
Water is essential for all living things, plants and animals. All organisms need water to maintain life processes. Some organisms live in water, some others breed only in water. Though the amounts of water required are different for different organisms, none can do entirely without it.
Water In Human Body:
Blood is mostly water, and muscles, lungs, and brain all contain a lot of water. Body needs water to regulate body temperature and for nutrients to travel to all organs. Water also transports oxygen to cells, removes waste, and protects your joints and organs. It is therefore very important to drink enough water everyday. For children the required intake of water is about 1-1.5 litres of water daily.
Water In Earth:
97% of the Earth’s water is in oceans. The ocean water cannot be directly used for daily needs because it is salty. 2% of the Earth’s water is frozen as ice-caps and glaciers. This cannot be easily used either. 1% of water is present in lakes, ponds, rivers, and under the ground. This is what we call fresh water. And that is what the entire Earth has for its use.
Three Forms of Water:
Liquid water is found in many places. Liquid water coming out of the faucet, when it rains, and running in a river are examples. Pure liquid water is free of salt, rocks, soil, and garbage.
Ice, snow, and frost are examples of water in the solid state. Liquid water freezes at 0 degrees Celsius. Celsius is scale that measures temperature.
Water as a gas—vapor is always present in the air around us. When you boil water, the water changes from a liquid to a gas or water vapor.
Sources of Water:
Rainwater, oceans, rivers, lakes, streams, ponds and springs are natural sources of water. Dams, wells, tube wells, hand-pumps, canals, etc, are man-made sources of water.
Water Cycle :
During part of the water cycle, the sun heats up liquid water and changes it to a gas by the process of evaporation. Water that evaporates from Earth’s oceans, lakes, rivers, and moist soil rises up into the atmosphere. The process of evaporation from plants is called transpiration. (In other words, it’s like plants sweating.) As water (in the form of gas) rises higher in the atmosphere, it starts to cool and become a liquid again. This process is called condensation. When a large amount of water vapor condenses, it results in the formation of clouds. When the water in the clouds gets too heavy, the water falls back to the earth. This is called precipitation. The rainwater runs over the ground’s surface runs into streams. It runs into rivers. With enough time, all the water makes its way back to the ocean. Water flows to the oceans. It has gone all the way around the water cycle. All the water that flows into the ocean once came out of the ocean.
Useful for CBSE, ICSE, NCERT & International Students
Grade : 2
Subject : Evs
Lesson : Air and Water
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