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CLASS 6 SCIENCE T3 WATER -TEXTBOOK SOLUTIOINS
Unit 2
Water
Evaluation
I. Choose the appropriate answer
1. Around 97% of water available on earth is water.
a. Fresh
b. pure
c. salty
d. Polluted
Ans: c. salty
2. Which of the following is not a part of water cycle?
a. evaporation
b. condensation
c. rain
d. Distillation
Ans: d. Distillation
3. Which of the following processes add water vapour to the atmosphere?
i. Transpiration
ii. Precipitation
iii. Condensation
iv. Evaporation
a. ii and iii b. ii and iv
c. i and iv d. i and ii
Ans: c. i and iv
4. About 30% of the fresh water is found in?
a. glaciers
b. ground water
c. other sources of water
d.0.3%
Ans: b. ground water
5. Using R.O. (Reverse Osmosis) plant at home eliminates lot of non-potable water. The best way to effectively use the expelled water of R.O. plant is ___________.
a. make the expelled water go and seep near the bore well
b. use it for watering plants
c. to drink the expelled water after boiling and cooling
d. to use for cooking as the water is full of many nutrients
Ans: b. use it for watering plants
II. Fill in the blanks
1. Only ____ percent of natural water is available for human consumption.
Ans: 0.3%
2. The process of changing water into its vapour is called ________ .
Ans: evaporation
3._______ is built on rivers to regulate water flow and distribute water.
Ans: Dam
4. Water levels in rivers increase greatly during _______.
Ans: rainy season.
5. Water cycle is also called as ________ .
Ans: Hydrological cycle
III. True or False. If False, give the correct statement
1. Water present in rivers, lakes and ponds is unfi t for use by human beings.
Ans: False. Water present in rivers, lakes and ponds is fit for use by human beings.
2. Seas are formed when the water table meets the land surface.
Ans: False. Ponds are formed when the water table meets the land surface.
3 The evaporation of water takes place only in sunlight.
Ans: True
4. Condensation results in the formation of dew on grass.
Ans: True
5. Sea water can be used for irrigation as Such.
Ans: False. Sea water can’t be used for irrigation as such.
IV. Match the following
Ans:
1. Flood - Increased rainfall
2. Surface water - Lake
3. Sunlight - Evaporation
4. Cloud - Water vapour
5. Frozen water - Pole
V. Arrange the following statements in correct sequence
1. These vapours condense to form tiny droplets of water.
2. The water droplets come together to form large water droplets.
3. The heat of the sun causes evaporation of water from the surface of the earth, oceans, lakes, rivers and other water Bodies.
4. The large water droplets become heavy and the air cannot hold them,
therefore, they fall as rains.
5. Water vapour is also continuously added to the atmosphere through transpiration from the surface of the leaves of trees.
6. Warm air carrying clouds rises up.
7. Higher up in the atmosphere, the air is Cool.
8. These droplets floating in the air along with the dust particles form clouds.
Ans:
1.The heat of the sun causes evaporation of water from the surface of the earth, oceans, lakes, rivers and other water bodies.
2.Water vapour is also continuously added to the atmosphere through transpiration from the surface of the leaves of trees.
3. Higher up in the atmosphere, the air is cool.
4.These vapours condense to form tiny droplets of water.
5.These droplets floating in the air along with the dust particles form clouds.
6.Warm air carrying clouds rises up.
7.The water droplets come together to form large water droplets.
8.The large water droplets become heavy and the air cannot hold them, therefore, they fall as rains.
VI. Analogy
1. Population explosion : Water scarcity :: Recycle :_________
Ans: Water management
2. Ground water : _________ :: Surface water : lakes
Ans: Tube Wells
VII. Give very short answer
1. Name four different sources of water
Wells,Lakes,Glacier and River.
2. How do people in cities and rural areas get water for various purposes?
In the city, people get water from water tanks, borewells and hand pipes. In rural areas, people get water from wells, canals, ponds and rivers.
3. Take out of cooled bottle of water from refrigerator and keep it on a table. After some time you notice a puddle of water around it. Why?
The air around the cooled surface of water bottles get cools and the air condenses as water vapour, so that puddle can be noticed after sometime.
4. We could see clouds almost every day. Why doesn’t it rain daily?
Clouds produce rain when the tiny droplets of liquid water begin to stick together,forming larger droplets. When these droplets get heavy, they fall as rain.
5. Name the places where water is found as ice.
Sea ice, Icecaps, Polar glaciers, ice-shelves, icebergs etc.
6. How do aquatic animals manage to live in Arctic and Antarctic Circle?
In the Arctic and Antarctic Circle, the water on the top of the lake or river freezes, but, underneath the frozen upper layer, the water remains in liquid form and does not freeze. The oxygen is also trapped beneath the layer of ice. As a result,aquatic animals find it possible to live comfortably in the Arctic and Antarctic Circle.
7. What are the types of rain water harvesting?
There are two types of rainwater harvesting.
a. Collecting water from where it falls.
(e.g): Collecting water from the rooftops of the houses or buildings (Roof water harvesting).
b. Collecting flowing rain water (e.g): Collecting rainwater by constructing ponds with bund.
VIII. Give short answer
1. Differentiate between surface water and groundwater.
2. Write a few slogans of your own on the topic “Save Water”.
“Save water, Save vigor”
“If you don’t save water, no one can save you”
“Aware the importance of saving water,beware the negligence of dripping water”
3. About 71% of earth’s surface is covered with water, then why do we face scarcity of water?
97% of the water available on the earth is saline water. Only 3% found is freshwater and that too in polar ice caps and glaciers. So this portion of water is not readily available for drinking, hence the scarcity arises.
4. Give reason for the following statement – Sewage should not be disposed of in rivers or oceans before treatment.
The wastewater generated by an individual and industry is referred to as sewage water. As it is contaminated with sludge,debris,effluents and feces, it should not be disposed of directly into rivers/oceans. It should be treated properly before letting out from home and industry.
5. The fresh water available on earth is only 3%. We cannot increase the
amount of water. In that case, how can sustain the water level?
Our activities like usage of plastics,deforestation, destruction of water sources and polluting the environment are causes for lowering of groundwater level.
We should pay more attention to conserving water.
Minimizing the usage of pesticides, insecticides, and fertilizers in agriculture.
Afforestation
Adopting to drip irrigation and sprinkler irrigation wherever possible.
Implementing a rainwater harvesting system in every house/building.
Adopting the best sewage water treatment system.
Creating awareness of throwing wastes into the water bodies and its impacts.
IX . Answer in detail
1. What is potable water? List down its characteristics.
Potable water is drinking water which is safe for human beings. It does not cause any harm to human health.
The potable water, should
Be colorless, odorless and neutral.
Free from harmful contaminants
Free from harmful microorganisms
Contain essential minerals
2. Who is known as waterman of India? Browse the net and find the details about the award, the waterman received for water management. State the findings by drafting a report.
The ‘Waterman of India’ is Dr. Rajendra Singh. He is a well-known water conservationist and environmentalist from Alwar district, Rajasthan. He got Ramon Magasaysay award for community leadership in 2001. In 2005, he got Jamnalal Bajaj award for Science and Technology for rural development. In 2008, The Guardian, named him amongst its list of 50 people who could save the planet. In 2015, he won Stockholm Water Prize. He runs an NGO called ‘Tarun Bharat Sangh’ (TBS), which was founded in 1975. In 2016, he was bestowed with Ahimsa Award by Institute of Jainology based in UK.
3. What is rainwater harvesting? Explain in a few sentences how it can be used in houses.
Direct collection and use of rain water is called rainwater harvesting. There are two types of rainwater harvesting.
a. Collecting water from where it falls. (e.g): Collecting water from the roof tops of the houses or buildings (Roof water harvesting).
b. Collecting flowing rain water (e.g): Collecting rainwater by constructing ponds with bund.
X. Question based on Higher Order Thinking Skills
1. When there is no pond or lake in an area, will there be formation of clouds possible in that area?
When there are no ponds or lakes in an area there won't be evaporation of surface water. So clouds cannot be formed in the above mentioned places.
2. To clean the spectacles, people often breathe out on glasses to make them wet. Explain why do the glasses become wet.
When we breathe out, the hot air comes out from our mouth, get condensed and changed into tiny water droplets and glasses become wet. The moisture thus formed helps us to clean the glass.
XI. CROSSWORD
DOWN
1. A method of water conservation.
Ans: Recycling
2. Process of getting water vapour from sea water.
Ans: Evaporation
6. Water stored in dams is used for generation of _______.
Ans:Electricity
ACROSS
3._______is a large body of non-potable water found in nature.
Ans: Ocean
4. In summer, the body loses water as________.
Ans: Sweat
5. Plants undergo _______and contribute to water cycle.
Ans: Transpiration
XII. (1). Observe the given graph carefully and answer the questions.
a. What percentage of water is seen in fish?
Ans: 70%
b. Name the food item that has maximum amount of water in its content.
Ans: Watermelon
c. Name the food item that has minimum amount of water in its content.
Ans: Fish
d. Human body consists of about percentage of water.
Ans: 60%
e. Specify the food item that can be consumed by a person when he / she is suffering from dehydration.
Ans: Watermelon
(2) Look at the map of Tamilnadu showing annual rainfall and answer
the questions given below
a. Identify the districts that get only low annual rainfall in Tamilnadu.
Dharmapuri, Erode, Karur, Trichy, Perambalur, Tanjore, Pudukottai, Sivagangai, Madurai, Dindigul, Ramanathapuram.
b. Identify the districts that get a medium annual rainfall in Tamilnadu.
Thiruvallur, Chennai, Kancheepuram, Krishnagiri, Vellore, Thiruvannamalai, Villupuram, Salem, Namakkal, Tirupur, Ariyalur, Thiruvarur, Virudhunagar, Tuticorin.
c. State the districts that enjoy high annual rainfall in Tamilnadu.
Nilgiri, Coimbatore, Theni, Thirunelveli, Kanyakumari, Cuddalore, Nagapattinam.
