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Air is pumped into clarified water to help aerobic bacteria to grow.

The impurities in water are called contaminants.

Water on the earth can exist in three forms 

ice (solid form), water (liquid form) and water vapour (gaseous form).

Nitrates, Phosphates, metals… etc are the inorganic impurities in water.

correct option is D) Rivers

Correct option is C) Evaporation

Correct option is B) Cucumber

Correct option is D) Phosphates

1. Microbes are doing a lot of service in breaking down the complex organic compounds in waste materials to simple structured substances. 

2. These substances ultimately becoming a manure. 

3. If there were no microbes, our life will be in danger. 

4. All the waste organic material remain as it was and pollute air and water posing a big problem to our survival.

Correct option is B) Chlorination

Correct option is C) aeration

Correct option is C) Aeration

Aquatic plants and animals make use of oxygen dissolved in water. Water gets polluted as the amount of oxygen in it decreases. Air is introduced into water to make up the quantity of oxygen.

Water in a landscape may be compared with the eyes on a human face because like the eyes, water reflects the mood of the hour. It looks bright and gay when the sun shines. It turns to dark and gloomy when the sky is overcast.

1. We dispose of wastewater in our daily life in different ways and means. 

2. We often see water stagnated near bore wells or beside houses. 

3. Sometimes human and animal excretions also mix with this water. 

4. We get a foul smell when we walk near those areas. 

5. To prevent this we need a proper drainage system.

1. Normally a lot of water flows out of the kitchen as well as bathrooms in our houses. 

2. Many of us do not know that water is being wasted in this way. 

3. We must make a channel of water to flow from kitchen to the garden around. 

4. We cannot wastewater from the bathroom also. It could be used after purification.

1. Water management :

• Bringing awareness to the people.
• Recycling water by separating pollutants.
• Minimize the use of fertilizers.
• Controlling deforestation.
• Adopt drip and sprinkler irrigation in agriculture.

2. Rainwater harvesting:

• Collecting water from where it falls:
• Collecting water from the roof tops.
• Collecting flowing rain water :
• Collecting rain water by constructing dams.

The year 2003 was observed as the International year of fresh water to make the people about the scarcity of fresh water.

Saving water for the future generations by using water carefully and in a limited way is conservation of water.

About 71% of the earth’s surface is covered with water and even then we face scarcity of water. 

Reasons:

1. 97% of total water is found in seas and oceans, which is salty and not fit for human consumption. 

2. Only 3% found is the freshwater and that too available in polar ice caps and glaciers. 

3. Out of 3% fresh water, only 0.3% is available to us as surface water, in lakes, rivers, and swamps.

Correct answer is (c) i and iv

1. On World Water Day, that is 22 March 2005, the period 2005 – 2015 was declared as the International Decade for action on “Water for Life”.

Polar ice-caps, Ice sheets and glaciers in Artie region arid Antarctica

The main reasons for scarcity of water are:

1. Population explosion.
2. Uneven distribution of rainfall.
3. Decline of ground watertable.
4. Pollution of water.
5. Careless use of water.

Correct answer is b. groundwater

(b) use it for watering plants

1. False. Water present in rivers, lakes and ponds is fit for use by human beings.

2. False. Ponds are formed when the water table meets the land surface.

3. True

4. True

5. False. Sea water cannot be used for irrigation as such.

Correct answer is (b) 0°C

Correct answer is (b) 3 – 4 litres

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 destruction. They may cause huge devastation.

Ponds, pools, rivers, tube wells have fresh water.

1. The sewage water treatment is to be adopted. 

2. Decrease the usage of pesticides, insecticides, and fertilizers in agriculture. 

3. Protect forest and trees. 

4. Adopt drip irrigation and sprinkler irrigation in agriculture. 

5. Rainwater harvesting should be implemented in every building. 

6. Create awareness about the impact of throwing wastes into the water bodies.

Correct answer is (b) Fresh

1. 0.3 

2. Evaporation 

3. Dam 

4. Raining

5. . Hydrological cycle

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

Correct answer is (c) Salty

(a) The water of the oceans is salty as it contains large amount of dissolved salts.
(b) 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.

Only fresh water is useful for humans, crops and vegetation and all living organisms. On the other hand, salty water is unsuitable for humans, crops and vegetation and all living organisms. Water is salty due to dissolved sodium chloride, calcium, magnesium salts and other particles.

Rain water when pours down to earth, it dissolves salts and flows into the sea by rivers. The continuous discharge of saline water into the sea makes the sea water salty.

Water is life. Without water, we can not think of life. Its scarcity may create num erous problems but its absence would definitely lead to non-existence of all the living beings on the earth. It is a precious resource of the nature. We drink water whenever we feel thirsty. We use water in numerous activities such as washing clothes, cleaning house floors, watering 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.

Ocean water is salty because it contains large amounts of undissolved salts.

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 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.

1. Water is essential for the germination of seed, growth of the plant and the photosynthesis. 

2. Water is used for the transportation of people and goods

The circulation of water between ocean and land is know as the Water cycle.

Sea and ocean water contains large amount of various salts, It is due to these salts the oceans water is salty and cannot be used for drinking, washing and for irrigation purposes.

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

Ocean movements can be classified into waves, tides and currents.
* 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.
* The rhythmic rise and fall of ocean water twice in a day is known as a tide. Tides may be high or low. It is high tide when water covers much of the shore by rising to its highest level. It is low tide when water falls to its lowest level and recedes from the shore. Tides are caused due to the strong gravitational pull exerted by the sun and
moon on the earth’s surface. High tides help in navigation and fishing. The rise and fall of water due to tides is being used to generate electricity in some places.
* Ocean currents. These are streams of water flowing constantly on the ocean surface in definite directions. The ocean currents may be warm such as the Gulf Stream and cold such as the Labrador Ocean current. The areas where the warm and cold currents meet provide the best fishing ground of the world. For example, seas around Japan and the Eastern Coast of North America.

Correct option is (a) processed