Water: Let's learn

 Water

Q.1. Answer the following questions briefly.

(a) What is precipitation?

(b) What is the water cycle?

(c) What are the factors affecting the height of the waves?

(d) Which factors affect the movement of ocean water?

(e) What are tides and how are they caused?

(f) What are ocean currents?

Ans.

(a) Precipitation refers to the falling of moisture in the form of rainfall, snow, fog, sleet, and hailstone.

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

(c) The factors affecting the height of the waves are winds, earthquakes, volcanic eruptions, or underwater landslides. The stronger the wind blows, the bigger the wave becomes.

(d) The factors affecting the movement of ocean water are temperature, winds, the gravitational pull of the sun, the earth, and the moon, as well as warm and cold currents.

(e) Tides are the rhythmic rise and fall of ocean water that occurs twice a day. The strong gravitational pull exerted by the sun and the moon on the earth's surface causes the tides.

(f) Ocean currents are streams of water flowing constantly on the ocean surface in definite directions.

Q.2. Give reasons:

(a) Ocean water is salty.

(b) The quality of water is deteriorating.

Ans.

(a) Ocean water is salty because it contains a large amount of dissolved salts.

(b) The quality of water is deteriorating due to industrial effluents and untreated water from industries mixing into streams and rivers, as well as sewerage water. As a result, the quality of water is deteriorating day by day.

Very Short Answer Type Questions-

Q.1. What is a terrarium?

Ans. A terrarium is an artificial enclosure for keeping small house plants.

Q.2. Which type of water do the ocean bodies and the seas contain?

Ans. They contain salty water.

Q.3. What do you mean by salinity?

Ans. Salinity is the amount of salt in grams present in 1000 grams of water.

Q.4. What is the average salinity of the oceans?

Ans. The average salinity of the oceans is 35 parts per thousand.Here is the rest of the text:

Q.5. What is the salinity of the Dead Sea?

Ans. The salinity of the Dead Sea is 45 parts per thousand.

Q.6. Why do swimmers float in the Dead Sea?

Ans. Swimmers float in the Dead Sea because the increased salt content makes it dense.

Q.7. What is the significance of World Water Day?

Ans. On the occasion of World Water Day (22nd March) the need to conserve water is reinforced in different ways.

Q.8. What is a Tsunami?

Ans. Tsunami is a Japanese word that means 'Harbour Waves' as the harbours get destroyed whenever there is a tsunami.

Q.9. What happens during high tide?

Ans. During high tide, waves rise high and water covers much of the shore.

Q.10. What happens during low tide?

Ans. During low tide, water falls to its lowest level and recedes from the shore.

Q.11. How are tides caused?

Ans. The strong gravitational pull exerted by the sun and the moon on the earth's surface causes tides.

Q.12. Name one warm current and one cold current.

Ans. Warm current — The Gulf Stream

Cold current — The Labrador Ocean current.

Q.13. What happened to the Indira Point during the tsunami of 2004?

Ans. It got submerged.

Short Answer Type Questions:-

Q.1. How are spring and neap tides formed?

Ans. 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. But when the moon is in its first and last quarter, the ocean waters get drawn in diagonally opposite directions by the gravitational pull of the sun and earth resulting in low tides. These tides are called neap tides.

Q.2. How are high tides important?

Ans. High tides are important for various reasons:

They help in navigation

They 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. Much more fish come closer to the shore during the high. This enables the fisherman to get a plentiful catch.

The rise and fall of water due to tides is being used to generate electricity in some places.

Q.3. What are the waves? Write a short note on it.

Ans. Waves are the rise and fall of the water on the surface of the ocean. 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 destructive. They may cause huge devastation.

Q.4. Write a brief note on Tsunami.

Ans. Tsunami is a Japanese word that means 'harbour waves' as the harbours get destroyed whenever there is a tsunami. An earthquake, a volcanic eruption, or underwater landslides can shift large amounts of ocean water. As a result, a tsunami occurs which may be as high as 15 m. The tsunami of 2004 is still in our minds. 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.

Q.5. Write a note on the importance of water.

Ans. Water is life. Without water, we cannot think of life. Its scarcity may create numerous problems, but its absence would definitely lead to the non-existence of all living beings on earth. It is a precious resource of nature. We drink water whenever we feel thirsty. We use water in numerous activities such as washing clothes, cleaning house floors, watering the garden, etc. Industries also need water for their functioning. Thus, water is very essential, and therefore, we must conserve it. Our careless use of water has created several problems. Whatever water is there, it is not of good quality. We should think about the ways of its conservation for our own sake.

Q.6. Explain the water cycle with a neat and labelled diagram.

Ans. The sun's heat causes evaporation of water, flowing down to stream or drains into water vapour. When the water vapour cools down, it condenses and forms clouds. These clouds, when they 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 continually changes its form and circulates between oceans, atmosphere, and land is known as the water cycle.