Water

Q19. Why rain clouds look grey in color?

Ans. As more and more water droplets gathers, clouds gets thicker, denser and less transparent. Thus, rain clouds look grey in color.

Q20. Where water in the taps comes from?

Ans. Water that we get from taps is drawn from a lake or a river or a well. It is then supplied through a network of pipes.

Q21. Sea water is not fit for drinking. Why?

Ans. Sea water is not fit for drinking because it has many salts dissolved in it which is not good for human body.

Q22. Water from wet roads, rooftops and a few other places disappears after the rains. Where does this water go?

Ans. Evaporation takes place from all open surfaces after the rains and water vapors gets continuously added to air. Thus, water disappears.

Q23. Dia kept two similar plates with equal amount of water, one in sunlight and other in her room. From which plate does water disappear first? Give reason.

Ans. Water disappears first from the plate kept in sunlight because in sunlight, evaporation takes place faster.

Q24. What would happen if we do not have easy access to water for a long period of time?

Ans. If we do not have easy access to water for a long period of time then we would not able to cook, clean utensils, wash clothes or bathe.

Q25. What are the two main natural sources of water?

Ans. The two main natural sources of water are:

      1.   Surface water – It includes rain water, river and lake water and sea water.

      2.   Underground water

 
Q26. How rain water is important?

Ans.  The rainwater fills up the lakes and ponds. A part of the rainwater gets absorbed by the ground. Some of this water is brought back to the air by the process of evaporation and transpiration.

Q27. Write two harmful effects of drought on plants?

Ans. Without adequate water, photosynthesis in plants are greatly reduced which affects the plants growth adversely. After many weeks of such condition, plants die out.

Q28. What do you understand by ground water?

Ans. A part of the rainwater gets absorbed by the ground and seems to disappear in the soil. This water available beneath the surface of the earth is called ground water.

Q29. List some of the activities for which we use water in a day.

Ans. We need water for many activities such as for drinking, bathing, brushing teeth, washing utensils, washing clothes, for toilet purpose, for cleaning floor etc.

Q30. First shower of rain water is not pure. Why?

Ans. First shower of rain water is not pure because while coming down through the air, the first showers collect dust particles, germs, bacteria and dissolve some of the gases which are present in the atmosphere.

 
Q31. Why water disappears from the bowl kept in the shade?

Ans. During the daytime air in surrounding gets heated. This warm air provides heat for evaporation of water in the shade. Thus, water disappears from the bowl kept in the shade.

Q32. From where do water drops appear on the outer side of the glass containing ice cubes?

Ans. The cold surface of the glass containing ice cools the air around it, and the water vapor of the air condenses on the surface of the glass. So, drops of water appear on outer surface of the glass containing ice.

Q33. How are clouds formed?

Ans. When the air moves up, it gets cooler and cooler. At sufficient heights, the air becomes so cool that the water vapor present in it condenses to form tiny drops of water called droplets. It is these tiny droplets that remain floating in air and appear to us as clouds.