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Important questions based on NCERT syllabus for Chapter 14 - Water:
Question-1: Why water from oceans and seas is unfit for drinking purpose?
Solution: Water in ocean and seas are salty because, many salts are dissolved in it. Salt dehydrates, so the more saltwater you drink, the more water your body loses. As you drink seawater, the water already present in your body is rerouted to help your body dilute the excess of salt. It is due to this fact water from oceans and seas are unfit for drinking.
Question-2: What happens to the water that rain and snow bring to different regions of earth?
Solution: Some of the water flows in the form of rivers and streams, the rain water also fills up the lakes and pond, a part of rain water gets absorbed by the ground and seems to disappear in the soil. Some of this water is brought back to the air by the process of evaporation and transpiration while the rest of it is stored underground in the form of groundwater.
Question-3: We have seen clouds countless number of times in our lives. How are clouds formed?
Solution: The water vapour present in sky are gas and cannot be seen. When air is cooled, each water vapour gathers and ties with neighbouring water vapour. Thus vapour forms many water drops, each of which consists of many water molecules. One drop is very small and can float in the air. (But when a drop is large enough they begin to fall as rain.) It cannot be seen but when very large number of drops gathers they are visible like fog or smoke. This is known as cloud. There are many chances when cloud is formed. For example towering thundercloud is formed when air rises high up in the sky.