5. Water

NCERT Solutions For Class 7 Geography Social Science Chapter 5 Water.

WATER-CYCLE
WATER CYCLE


Questions.1.Answer the following questions.  

 (a) What is precipitation?
Answer.- Falling of moisture in the form of rainfall, snow, fog, sleet, and hailstone is termed as precipitation.

(b) What is water cycle?
Answer.- The water cycle is the process by which water continually changes its form and circulates between oceans, atmosphere, and land.

 (c) What are the factors affecting the height of the waves?
Answer.- Winds, earthquakes, volcanic eruption, or underwater landslides are the factors affecting the height of the waves. The stronger the wind blows, the bigger the wave becomes.

 (d) Which factors affect the movement of ocean water?
Answer.- Temperature, winds, the gravitational pull of the sun, the earth, and the moon; warm and cold currents are the factors that affect the movement of ocean water.

 (e) What are tides and how are they caused?
Answer.- Tides are the rhythmic rise and fall of ocean water that occurs twice in a day. The strong gravitational pull exerted by the sun and the moon on the earth’s surface cause the tides.

 (f) What are ocean currents?
Answer.- Ocean currents are streams of water flowing constantly on the ocean surface in definite directions.
                                   
Question.2  Give reasons.

(i) Ocean water is salty.
Answer.-The ocean bodies and the seas contain salty water. The water of oceans is salty or saline as it contains large amount of dissolved salts. Most of this salt is sodium chloride.
 
(ii) The quality of water is deteriorating.
Answer.- Though three-fourth of the Earth’s surface is covered with water, almost 98% of it is unfit for use. Oceans and seas, which constitute the major portion of the hydrosphere, contain saline water. The fresh water reserves of the Earth are mostly made up of ice-caps, ground water, lakes and rivers. The quantity of water on Earth remains the same. It constantly changes form and circulates between oceans, atmosphere and land. Considering that the fresh water reserves remain constant and that the world population rises day-by-day, it is important that we use these water resources judiciously. However, due to factors like deforestation, industrial and agricultural pollution of rivers and lakes, wastage of water, pollution of ground water, etc., the quality of water that is available to many people in this world today is not suitable for human consumption.
                               
Question.3 Tick the correct answer.
 
(i) The process by which water continually changes its form and circulates between oceans, atmosphere and land
(a) Water cycle
(b) Tides
(c) Ocean currents
 
(ii) Generally the warm ocean currents originate near
(a) Poles
(b) Equator
(c) None of these
 
(iii) The rhythmic rise and fall of ocean water twice in a day is called
(a) Tide
(b) Ocean current
(c) Wave
 
Answer.-
(i)- (a) Water cycle
(ii)- (b) Equator
(iii)- (a) Tide
 
Question. 4 Match the following.
Answer.-
 

(i) Caspian Sea

(a) Largest lake

(ii) Tide

(b) Periodic rise and fall of water

(iii) Tsunami

(c) Strong seismic waves

(iv) Ocean currents

(d) Streams of water moving along definite paths
 
EXTRA QUESTION
 
1. What is the salinity of the Dead sea?
Answer.-  45 parts per thousand.
2. What is a Tsunami?
Answer.- Tsunami is a Japanese word that means ‘Harbour Waves’ as the harbors get destroyed whenever there is a Tsunami.
3.What happened to the Indira point during the tsunami of 2004?
Answer.- It got submerged.
4. What is the significance of World Water Day?
Answer.- World Water Day (22nd March) the need to conserve water
5. What do you mean by salinity?
Answer.- Salinity is the amount of salt in grams present in 1000 grams of water.
6. What is a terrarium?
Answer.- It is an artificial enclosure for keeping small house plants. .