These DAV Class 7 SST Book Solutions Pdf and DAV Class 7 SST Chapter 5 Question Answer – Water Surrounding the Earth are thoughtfully prepared by experienced teachers.
DAV Class 7 SST Ch 5 Question Answer – Water Surrounding the Earth
DAV Class 7 SST Ch 5 Solutions – Water Surrounding the Earth
Something To Know
A. Tick (✓) the correct option.
Question 1.
The water cycle is
(a) the continuous movement of water
(b) passage of water through a house
(c) the life of an organism in water
(d) a static system.
Answer:
(a) the continuous movement of water
Question 2.
The three states of water are
(a) cloud, rain, river
(b) solid, liquid, gas
(c) salt water, fresh water, rainwater
(d) waves, tides, currents
Answer:
(b) solid, liquid, gas
Question 3.
What turns water on the earth into vapours in the water cycle?
(a) the core of the earth
(b) global warming
(c) the sun
(d) nuclear energy
Answer:
(a) the core of the earth
Question 4.
When clouds get too heavy to hold water
(a) the water runs off.
(b) the waterfalls on the earth.
(c) more clouds are formed.
(d) water gets collected.
Answer:
(b) the waterfalls on the earth.
Question 5.
Which is the only warm current from among the following?
(a) Oyashio
(b) Canary
(c) Kuroshio
(d) Labrador
Answer:
(c) Kuroshio
B. Fill in the blanks.
1. The largest natural source of water is ……………
2. When the level of ocean water rises, it is a ……………. tide.
3. …………… port in India is an example of tidal port.
4.The Gulf stream takes its name from the Gulf of ………….
5. ………….. is a cool current on the west coast of South America.
Answer:
1. rain
2. high
3. Kolkata
4. Mexico
5. Humboldt
C. Give a technical term for each of the following statements.
Question 1.
The process in which water is converted to water vapours through the heat of the sun.
Answer:
Evaporation.
Question 2.
The continuous circulation of water in the three spheres of the earth.
Answer:
Water cycle.
Question 3.
A movement in the ocean in which water particles move up and down.
Answer:
Waves.
Question 4.
It is the purest form of water.
Answer:
Rainwater.
Question 5.
Periodic rise and fall in the level of the ocean water.
Answer:
Tides.
D. Answer the following questions in brief.
Question 1.
On what factors does the height of a wave depend?
Answer:
The height of a wave depends on the speed of wind and the duration of wind blowing from a particular direction.
Question 2.
Define an ocean current.
Answer:
An ocean current is a continuous movement of a mass of water in a particular direction.
Question 3.
How are tides caused?
Answer:
Tides are caused due to the gravitational pull of the Moon and the Sun.
Question 4.
Name the important components of the water cycle.
Answer:
Evaporation, Precipitation and Condensation.
Question 5.
Name three valuable resources which are found in abundance in the ocean.
Answer:
Food, mineral oil and energy.
E. Answer the following questions.
Question 1.
How are tides useful to us?
Answer:
(a) Tides help in navigation. High tide enables ships to enter the harbour or sail out of the harbour.
(b) Low tides are used by fishermen to go out into the sea for fishing. They return back with the incoming of high tide.
(c) During high tide, when the water gushes in towards the land, lots of fish comes along with it. This help fishermen to catch fish easily.
(d) Tidal energy can be harnessed to generate electricity in the coastal areas.
Question 2.
How are oceans beneficial to us in improving the quality of life?
Answer:
Oceans are beneficial to us in the following way:
- The oceans facilitate countries and regions to trade with one another. Goods can be moved in a very large quantity by ships and the transportation is cheaper than any other mode of transport.
- The marine environment provides animal and plant life for food and source of food.
- Some of the valuable mineral resources like mineral oil, manganese, nodules, gold, platinum, nickel, etc. are also found in the ocean floor. Several countries are tapping mineral oil as . a source of energy in a big way. However, the exploitation of the deep ocean floor is not an easy task.
Question 3.
Explain the water cycle with the help a diagram.
Answer:
Water is available in abundance on the earth’s surface. This water is converted into water vapours due to the heat of the sun by the process of evaporation. The evaporated vapours rise up in the atmosphere and condense into tiny crystals of ice or droplets of water to form clouds. When the condensed ice crystals or water droplets become too heavy to float into air, they come down as precipitation. This process never stops and is known as water cycle.
Question 4.
Examine three effects of ocean currents.
Answer:
(a) The ocean currents influence the climate of the coastal regions of the continents. If a warm current passes along the coast, it brings about warm temperature over land surface. Similarly, cold currents make the adjoining coastal region colder.
(b) In coastal areas, warm ocean currents cause rainfall and, therefore, influence its climate, making it warm and moist. The cold currents tend to make the climate cool and dry. Thus, ocean currents modify the climate in the coastal regions.
(c) The areas where the warm and cold currents meet provide ideal conditions for plentiful growth of plankton, which is a food for the marine life. These areas serve as the best fishing grounds.
Question 5.
Suggest four ways to help people affected by devastation due to Tsunami.
Answer:
- Providing relief to the victims by donating money, clothes, etc.
- Making relief camps for the affected people.
- Making arrangements for dropping food and medicines via air.
- Making arrangements for boats and other floating objects so that people can be rescued to safer places.
- Epidemics of diseases like cholera, malaria very quickly after tsunami. So, advising people to be careful is also important.
Value Based Question
Question 1.
We should respect and protect our oceans and seas. Oceans made Earth a habitable planet by giving birth to life. But
- we are turning our oceans into dumping grounds of waste material.
- What steps should be taken to prevent loss of precious marine life?
Give two suggestions to ban the disposal of waste material into oceans and seas.
Answer:
Do yourself with the help of Internet and other sources.
Map Skill
Locate and label the following on the outline map of the world.
(a) Labrador Current
(b) Gulf Stream
(c) North Atlantic Drift
(d) Grand Banks Fishing Ground
(e) Dogger Banks Fishing Ground
Answer:
Something To Do
Question 1.
Prepare a small working model of ocean currents over a thermocol sheet. Use coloured electric wires to show the distribution of cold and warm currents.
Answer:
Do yourself with the help of the map of major ocean currents.
Question 2.
Collect pictures of different marine resources present in the ocean.
Answer:
Do yourself.
Question 3.
Collect pictures of a coastal region showing the devastation of land, trees, houses and lives caused by huge oceanic waves.
Answer:
‘Do yourself. Take help of the Internet.
Question 4.
Collect pictures of coastal region in India where corrective action has been taken to preserve water bodies and natural vegetation and wildlife.
Answer:
Do yourself.
DAV Class 7 Social Science Chapter 5 Question Answer – Water Surrounding the Earth
A. Tick (✓) the correct option.
Question 1.
Plants return water to the atmosphere in the form of moist air through their
(a) leaves
(b) barks
(c) roots
(d) branches
Answer:
(a) leaves
Question 2.
Water can be saved by
(a) making slanting roofs of the houses
(b) storing of surplus water in reservoirs
(c) curtailing our needs of water
(d) None of the above
Answer:
(b) storing of surplus water in reservoirs
Question 3.
Cold currents make the climate of the coastal area
(a) cool and dry
(b) cool and moist
(c) moist
(d) warm and dry
Answer:
(a) cool and dry
Question 4.
Tides occur
(a) once a day
(b) twice a day
(c) thrice a day
(d) quarter a day
Answer:
(b) twice a day
Question 5.
Which one of the following is an example of warm ocean current?
(a) Labrador
(b) California
(c) Gulf Stream
(d) Peru
Answer:
(c) Gulf Stream
B. Very Short Answer Type Questions
Question 1.
How is groundwater formed?
Answer:
A small part of rainwater percolates inside the earth. This forms groundwater.
Question 2.
In which form is water present in high-altitude regions?
Answer:
Water is present in high-altitude regions in the form of ice crystals.
Question 3.
How are ocean currents formed?
Answer:
Ocean currents are formed due to the heating and cooling of the ocean water.
Question 4.
Why does cold water sink down below the warm water?
Answer:
The density of cold water is higher than that of warm water.
Question 5.
What happens when a warm current passes along the coast?
Answer:
The temperature of coastal regions raises making the place warmer than its surrounding areas.
Question 6.
What is the time interval between a high tide and a low tide?
Answer:
It is 6 hours 13 minutes.
Question 7.
Mention one advantage of the ocean currents.
Answer:
The ocean currents help in navigation.
Question 8.
When is it a high tide and when is it a low tide?
Answer:
When the level of ocean water rises, it is a high tide and when the level falls, it is a low tide.
Question 9.
How is high tide good for big ships?
Answer:
High tide enables big ships to enter the harbour or sailent of the harbour.
Question 10.
Give one advantage of tidal energy.
Answer:
Tidal energy is harnessed nowadays to generate electricity in the coastal areas.
Question 11.
What role did media play during the time of tsunami?
Answer:
It mobilised public help for the victims.
Question 12.
Name one warm current and one cold current.
Answer:
Warm current-Kuroshio; cold current-canary.
Question 13.
What is plankton?
Answer:
Plankton is a food for the marine life.
Question 14.
Name four major oceans on the earth.
Answer:
The Pacific, Atlantic, Indian and Arctic.
Question 15.
Why is the temperature in the coastal area different from that in the interior of the continent?
Answer:
It is because in coastal areas warm ocean currents influence its climate but the interior of the continent remains unaffected.
C. Short Answer Type Questions
Question 1.
Why is it necessary to make judicious use of water?
Answer:
Water is not uniformly distributed on the earth. Some areas receive heavy rainfall or snowfall which increases water supply and makes it surplus there. On the other hand, there are areas which receive poor rainfall or snowfall. In these areas people suffer due to scarcity of water. Hence, it is necessary to regulate water resource by storing of surplus water in larger reservoirs. Water can be conserved in several other ways too. Thus, it is necessary to use water judiciously otherwise the problem of water scarcity would persist.
Question 2.
What do you mean by ocean currents? How are they caused?
Or
Write a short note on ocean currents.
Answer:
Ocean currents are streams of water moving continuously on the ocean surface in a particular direction. Ocean currents are of two types – cold currents and warm currents. These are formed due to heating and cooling of the ocean water. Cold water being denser than the warm water sinks down below the warm water. Thus, the cold water of the polar region moves slowly towards the equator along the bottom of the ocean. The warm water near the equator moves along the surface of the ocean towards the poles. In this way, ocean currents are caused.
Question 3.
What are tides? Mention any three advantages of high tides.
Answer:
Tides are the periodic rise and fall in the level of ocean water. They are cuased due to the gravitational pull of the moon and the sun. When the level of water rises, it is a high tide and when the level falls, it is a low tide.
Advantages of High Tides:
- High tides help in navigation. They raise the water level close to the shores. This helps the ships to arrive at the harbour or sailout of the harbour more easily.
- High tides help in fishing. Fishermen get a plentiful catch.
- Tidal energy is harnessed to generate electricity in the coastal areas.
Question 4.
What happens to the rain water when it falls on the earth’s surface?
Answer:
The sun’s heat causes water to evaporate. The evaporated vapours rise up in the atmosphere and condense into tiny crystals of ice or droplets of water to form clouds. When the condensed ice crystals or water droplets grow in size and are unable to float, they fall down over the earth’s surface as precipitation.
Question 5.
Differentiate between warm and cold ocean currents.
Answer:
(a) The warm ocean currents originate near the equator and move towards the poles. The cold currents carry water from polar or higher latitudes to tropical or lower latitudes.
(b) The warm currents flow along the east coast of the continents while cold currents flow along the west coast.
D. Long Answer Type Questions
Question 1.
Describe various movements of ocean water.
Answer:
The various movements of ocean water are-waves, ocean currents and tides.
(i) Wave. They are the movements in water body where water particles move up and down. The height of waves depends on the speed of wind and the duration of wind blowing from a particular direction. It also determines the size of a wave. During storms, the winds belowing at very high speed form huge waves. These may cause huge destruction.
(ii) Ocean Currents. The are streams of water moving continuously on the ocean’s surface in a definite direction. These are of two types— cold currents and warm currents. They are formed due to heating and cooling of the ocean water. The warm ocean currents originate near the equator and move towards the poles. The cold currents carry water from polar or higher latitudes to tropical or lower latitudes.
(iii) Tides. The are the periodic rise and fall in the level of coean water. They are caused due to the gravitational pull of the moon and the sun. They occur twice a day when the level of water rises, it is a high tide and when the level falls, it is a low tide.
Question 2.
Prepare a small report on the destruction caused by Tsunami, 2004 in India.
Answer:
The earthquake and resulting tsunami affected many countries in Southeast Asia and beyond, including Indonesia, Sri Lanka, India, Thailand, the Maldives, Somalia, Myanmar, Malaysia, Seychelles and others. Many other countries, especially Australia and those in Europe, had a large number of citizens travelling in the region on holidays. Sweden lost 543 citizens in the disaster, while Germany identified 539 victims. (Students can add more information to this).