DELHI PUBLIC SCHOOL TAPI

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1 DELHI PUBLIC SCHOOL TAPI CLASS VII Learning Partnership 5 (KEY) Water : LESSON 5: Water (KEY) Writing Task: W.B (pp-136) 1. What are the 3 main process involved in the water cycle. Evaporation, Condensation, Precipitation 2. What is water cycle? The water cycle is the process by which water continually changes its form and circulates between oceans, atmosphere and land 3. What is a terrarium? Why is the Earth compared to it? It is an artificial enclosure for keeping small house plants. Earth is the place that supports life and is so compared to a terrarium. 4. Name the major sources of fresh water. Rivers, ponds, springs, glaciers 5. Why is the water in the oceans and sea salty? The water of the oceans is salty as it contains large amount of dissolved salts. 6. ¾ of the earth surface is covered with water. 7. Define salinity. Salinity is the amount of salt in grams present in 1000 grams of water 8. What is the average salinity of the oceans? The average salinity of the oceans is 35 parts per thousand Writing Task: W.B (pp136,137) 1. Why can the swimmers float in the Dead Sea? Swimmers float in Dead sea because the increased salt content makes it dense. 2. Why is water important to us? As it is the main component for the existence of life on earth. 3. Why is March 22 nd celebrated as World Water Day? On the occasion of World Water Day (22nd March) the need to conserve water is reinforced in different ways. 4. In which forms does the water move in the oceans? Waves, tides, currents Writing Task: W.B (pp- 137) 1. What are waves? Waves are the rise and fall of the water on the surface of the ocean 2. How are waves caused? Waves are formed when winds scrape across the ocean surface. The stronger the wind blows, the bigger the wave becomes. During the storm, the winds blow at very high speed and therefore huge waves are formed. These waves are very strong, hence very destruction. They may cause huge devastation.

2 3. What determines the size of the waves? Winds 4. A huge tidal wave caused by an earthquake is called Tsunami. 5. What is a tide? The rhythmic rise and fall of ocean water twice in a day is called a tide. 6. When the water falls to its lowest level and recedes from the shore it is low tide. 7. How are tides caused? The strong gravitational pull exerted by the sun and the moon on the earth s surface causes tides. 8. What is the difference between high tide and low tide? During high tide waves rise high and water covers much of the shore During low tide water falls to its lowest level and recedes from the shore 9. Define spring tides. During the full moon and new moon days, the sun, the moon and the earth are in the same line and the tides are highest. These tides are called spring tides. 10. What are neap tides? When the moon is in its first and last quarter, the ocean waters get drawn in diagonally opposite directions by the gravitational pull of sun and earth resulting in low tides. These tides are called neap tides. Writing Task: W.B (pp-139) Differentiate between: 1. Evaporation and Condensation The sun s heat causes evaporation, heating of the water vapour. When water vapour cools down it causes condensation 2. Fresh water and Saline water Water in the rivers, lakes, ponds, springs etc are ex. Of fresh water as they are not saline. The ocean water is saline because of the dissolved salts in high amount. 3. Water of ponds and that of oceans. (Written earlier) 4. Waves and Tides. (Written earlier) Give Reasons: 1. Ocean water is salty. The water of the oceans is salty as it contains large amount of dissolved salts. 2. The quality of water is deteriorating Water is being used injudiciously. Whatever potable water is available, its quality is not good. It is because industrial effluents and untreated water of industries get mixed into streams and rivers. Swerage water also gets mixed into these water bodies. As a result, the quality of water is deteriorating day by day 3. The size of the wave is much larger on a windy day than on a normal day. As the winds blow at a huge speed effecting the size of the waves too. Answer: a) Spring Tide b) i- Sun ii- Moon iii- Earth W.B (pp- 137,138) 1. What does the word Tsunami mean? Tsunami is a Japanese word that means harbour waves as the harbours get destroyed whenever there is tsunami. 2. To what height has a Tsunami wave risen so far? 1720 ft tall 3. What destruction was caused in India by the Tsunami in 2004? The tsunami of 2004 is still in our mind. It caused huge death and destruction in the coastal areas of India. The Indira point in the Andaman and Nicobar Islands got submerged after the tsunami

3 4. What are Ocean currents? Ocean currents are streams of water flowing constantly on the ocean surface in definite directions. The ocean currents may be warm or cold. 5. How are Ocean currents caused? The ocean currents may be warm or cold. The warm ocean currents originate near the equator and move towards the poles. The cold current carry water from polar or higher latitudes to tropical or lower latitudes. For example the Labrador Ocean current is cold current while the Gulf Stream is a warm current. The ocean current influence the temperature conditions of the area. Warm currents bring about warm temperature over land surface. The areas where the warm and cold currents meet provide the best fishing grounds of the world. For example seas around Japan and the eastern coast of North America. The areas where a warm and cold current meet also experience foggy weather and therefore navigation becomes difficult. 6. Give an example of a warm current and a cold current. The Labrador Ocean current is cold current while the Gulf Stream is a warm current. 7. What is the effect of cold and warm currents on the neighbouring lands? The ocean current influence the temperature conditions of the area. Warm currents bring about warm temperature over land surface. The areas where the warm and cold currents meet provide the best fishing grounds of the world. For example seas around Japan and the eastern coast of North America. The areas where a warm and cold current meet also experience foggy weather and therefore navigation becomes difficult. 8. Which is the most important occupation in areas where warm currents meet the cold ocean currents? Fishing W.B (pp- 140, 141) Very Short Answer: a) What is the percentage of ground water found on the Earth? 0.68% b) Give the location of the Labrador current. North Atlantic Ocean c) Name the areas, which were worst affected by Tsunami in India. AP, Tamil Nadu, Kerela, Puducherry, Andaman and Nicobar Islands Short Answer: a) Name 2 areas in the world where the fishing grounds are famous. Give reason regarding their location. Seas around Japan and the eastern coast of N. America This is the place where warm and cold currents meet. b) Mention 2 ways in which water is polluted. Factory outlets, Bathing in the water c) What are the different movements that occur in the oceans. Waves, currents, Tides d) Which factors affect the movement of ocean water. ) Temperature, winds, 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 is precipitation? Falling of moisture in the form of rainfall, snow, fog, sleet and hailstone is termed as precipitation Writing Task: W. B (pp-141, 142) Long Answers (In N.B) a) What is water cycle? The sun s heat causes evaporation of water, flowing down to stream or drains into water vapour. When the water vapour cools down, it

4 condenses and forms clouds. These clouds, when become too heavy to float, start falling on the land or sea in the form of rain, snow or sleet. Thus, the process by which water continuously changes its form and circulates between oceans, atmosphere and land is known as the water cycle. b) What are the factors affecting the height of the waves? When the water on the surface of the ocean rises and falls alternately, they are called waves. Waves are formed when winds scrape across the ocean surface. The stronger the wind blows, the bigger the wave becomes c) What causes the formation of Tsunami in the Indian Ocean? Explain. After thrusting of the Indian plate below the Burma plate, the water mass rushed back towards the coastline. Tsunami travelled at a speed of 800km per hour. Comparable to speed of commercial aircraft and completely washed away some of the islands in the Indian Ocean. The Indira Point in thje Andaman and Nicobar islands got completely submerged. d) How are high tides beneficial to man? : High tides are important for various reasons: They help in navigation The raise the water level close to the shores. This helps the ships to arrive at the harbour more easily. The high tides also help in fishing. Many more fish come closer to the shore during the high. This enables the fisherman to get a plentiful catch.

5 The rise and fall of water due to tides is being used to generate electricity in some places. e) What are the main reasons behind the major damage caused by Tsunami? Suggest any 2 ways to minimize the casualities. (1 st part written earlier) 2 nd Part: a) It is possible to give a three hour notice of the tsunami b) One should not go for navigation or catching fish in such situations (W.B pp- 138,139) Multiple Choice: a) Warm currents generally originate near the equator. b) Tides which occur during full moon and new moon are known as spring tides. c) The rise and fall of ocean water twice in a day is called a _tide. d) World Water Day is celebrated on 22 March. e) Tsunami is a _japanese_word. Tick the correct answer: a) The process by which water continually changes its form and circulates between oceans, atmosphere and land : i b) Generally the warm ocean currents originate near equator c) The rhythmic rise and fall of ocean water twice a day is called tide Fill in the blanks: a) The condensation of water vapour causes the formation of rain. b) The circulation of water between oceans, atmosphere and land is known as the water cycle c) The river Amazon flows in S. America. d) The southern ocean surrounds the continent of Antarctica True/False: a) The Ganga is among the ten dying rivers.t b) The Indira Point was submerged after the Tsunami in T c) An earthquake can be predicted. T d) Tides are caused by the gravitational pull of the moon only. F Match the following: a) Salt ii i) Bigger waves b) Dead Sea iii ii) Sodium Chloride c) Stronger winds i iii) Israel Match the following: a) Caspian Sea i i) Largest Lake b) Tide ii ii) Periodic rise and fall of water c) Tsunami iii iii) Strong Seismic waves d) Ocean Currents iv iv) Streams of water moving along definite Paths v) Water Cycle CONCLUDED