Class 7 Social Studies

Chapter Water: Our Lifeline Solution & Ans

A. Darken the correct option in OMR sheet:

1. The largest ocean is the ________ ocean.

(a) Pacific

(b) Atlantic

(c) Indian

(d) None of these

Answer: (a) Pacific

2. ________ of the earth's surface is covered with water.

(a) 71%

(b) 60%

(c) 90%

(d) None of them

Answer: (a) 71%

3. The ________ water is saline.

(a) Sea

(b) Tap

(c) Pond

(d) None of these

Answer: (a) Sea

B. Fill in the blanks:

1. All water bodies on the earth's surface are collectively called __________.

Answer: Hydrosphere

2. __________ occurs in a variety of forms hail, rain, sleet, fog, mist and dew.

Answer: Precipitation

3. Many living beings need __________ to survive.

Answer: Water

4. Only 1% of the fresh water is found in liquid form on the surface of the Earth as __________ and __________.

Answer: Rivers and Lakes

5. The ocean water is __________.

Answer: Saline

6. Some of the chemicals that are flown into ocean water act as __________ to the growth of __________.

Answer: Nutrients, Plankton

7. Labrador (North America) which is in the same latitude, remains frozen for nine months due to __________ current.

Answer: Labrador Cold

C. Write 'T' for true and 'F' for false statements:

1. North Atlantic Current is a cold current.

Answer: F

2. The salinity of water is same everywhere.

Answer: F

3. Tides are caused by wind.

Answer: F

4. Big waves do not depend on the force of the wind.

Answer: F

D. Answer the following questions in short:

1. What is the hydrosphere?

Answer: The hydrosphere is the total amount of water present on the Earth, including oceans, seas, rivers, lakes, glaciers, groundwater and water vapour in the atmosphere.

2. What do you mean by watershed management?

Answer: Watershed management is the proper planning, conservation and management of water and land resources in a drainage area to prevent soil erosion and conserve water.

3. What are tides?

Answer: Tides are the regular rise and fall of sea water caused mainly by the gravitational pull of the Moon and the Sun.

4. What is called drift?

Answer: The movement of ocean water driven by the prevailing winds over long distances is called drift.

E. Answer the following questions in detail:

1. Why is the earth known as 'watery planet'?

Answer:

The Earth is known as the 'Watery Planet' because about 71% of its surface is covered with water. Most of this water is found in oceans and seas, while only a small part is available as fresh water in rivers, lakes and groundwater. Water is essential for all living organisms, making the Earth unique among the known planets.

2. What is water cycle?

Answer:

The water cycle is the continuous movement of water between the Earth's surface and the atmosphere. It includes evaporation, condensation, precipitation and collection. This natural process ensures a continuous supply of fresh water on Earth.

3. How are tides useful?

Answer:

Tides help in navigation by allowing ships to enter and leave harbours safely. They also help fishermen in fishing activities, prevent the accumulation of pollutants near the coast and are used to generate electricity through tidal energy.

4. In what ways the ocean currents influence the climate?

Answer:

Ocean currents influence the climate by transferring heat from one region to another. Warm currents increase the temperature of nearby coastal areas, while cold currents lower it. They also affect rainfall, humidity and weather conditions, making some regions warmer, cooler, wetter or drier.