Water — Exercise Solutions Guide
This page covers every exercise question from Samacheer Kalvi 6th Science, Term 3, Chapter 2: Water. Solve each question yourself first, then check the solutions below.
I. Choose the Appropriate Answer (MCQs)
Q1. Around 97% of water available on earth is \_\_\_\_\_ water.
(a) fresh (b) pure (c) Salty (d) polluted
About 97% of the earth's water is found in seas and oceans as saline (salty) water, unfit for direct human consumption.
Q2. Which of the following is not a part of the water cycle?
(a) evaporation (b) condensation (c) rain (d) distillation
Evaporation, condensation, and rain (precipitation) are natural processes in the water cycle. Distillation is an artificial process used to purify water — it is not part of the natural cycle.
Q3. Which 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
Transpiration (from plant leaves) and evaporation (from water bodies) both release water vapour into the atmosphere. Precipitation removes water vapour; condensation converts it to liquid.
Q4. About 30% of the freshwater is found in \_\_\_\_\_?
(a) glaciers (b) groundwater (c) other sources of water (d) 0.3%
Of the 3% freshwater on earth, about 30.1% exists as groundwater beneath the earth's surface.
Q5. Using R.O. plant at home eliminates a 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 after boiling and cooling (d) to use for cooking
The expelled water still contains some minerals but is safe for plants. This is a practical way to conserve water at home.
Additional MCQs
Q6. \_\_\_\_\_ form of water is present in the mountain and polar regions.
(a) Solid (b) Liquid (c) Gaseous (d) All these
In polar and high mountain regions, water exists as ice and snow — its solid form.
Q7. The melting point of ice is \_\_\_\_\_.
(a) 100 °C (b) 0 °C (c) 0.100 °C (d) 10 °C
Ice melts into liquid water at 0 °C under normal atmospheric pressure.
Q8. \_\_\_\_\_ water contains 0.05% to 1% of salts.
(a) Brackish (b) Fresh (c) Sea (d) Sewage
Freshwater has low salinity (0.05% to 1% dissolved salts), distinguishing it from brackish and seawater.
Q9. The human body requires \_\_\_\_\_ litres of water per day for proper functioning.
(a) 2–3 litres (b) 3–4 litres (c) 4–5 litres (d) 1–2 litres
The human body needs approximately 3–4 litres of water daily for temperature regulation, digestion, and toxin removal.
Q10. In plants, the loss of water in vapour form from aerial parts is through \_\_\_\_\_
(a) Root (b) Shoot (c) Stomatal Pores (d) Fruit
Transpiration occurs through stomatal pores on the surface of leaves, releasing water vapour into the atmosphere.
Q11. \_\_\_\_\_ water is obtained through open wells, tube wells, or hand pumps, springs.
(a) Surface (b) Frozen (c) Saline (d) Ground
Groundwater is accessed through wells, tube wells, hand pumps, and natural springs.
Q12. \_\_\_\_\_ of Asia's largest rivers flow from the Himalayas.
(a) 10 (b) 9 (c) 11 (d) 15
Ten of Asia's major rivers originate from the Himalayan glaciers, supplying water to billions of people.
Q13. Volume of liquid is measured by \_\_\_\_\_
(a) Gallon (b) Litre (c) Cusec (d) TMC
Litre is the standard unit for measuring the volume of a liquid. Cusec measures flow rate, not static volume.
Q14. \_\_\_\_\_ forests are found in Pichavaram near Chidambaram.
(a) Green (b) Grasslands (c) Mangrove (d) Estuaries
Pichavaram near Chidambaram in Tamil Nadu has one of the largest mangrove forests in India, serving as a vital coastal ecosystem.
II. Fill in the Blanks
1. Only \_\_\_\_\_ percent of natural water is available for human consumption.
2. The process of changing water into its vapour is called \_\_\_\_\_
3. \_\_\_\_\_ is built on rivers to regulate water flow and distribute water.
4. Water levels in rivers increase greatly during \_\_\_\_\_
5. Water cycle is also called as \_\_\_\_\_
Additional Fill in the Blanks
6. \_\_\_\_\_ plays a vital role in the evolution and survival of life.
7. \_\_\_\_\_ is present in the air around us.
8. In the distribution of a total of 0.3% of surface water, \_\_\_\_\_ has 87% surface water.
9. The molecular formula of water is \_\_\_\_\_
10. The oceanic volcanoes also add \_\_\_\_\_ to the sea.
11. Every year \_\_\_\_\_ is observed as the World Water Day.
12. The water vapour gets cooled and changes into tiny water droplets that form \_\_\_\_\_ in the sky.
13. A larger portion of water — \_\_\_\_\_% of the total available freshwater — is in a frozen state.
14. The water level in the reservoirs is measured in \_\_\_\_\_
15. Adoption of \_\_\_\_\_ and \_\_\_\_\_ irrigation in agriculture.
III. True or False (If False, give the correct statement)
Q1. Water present in rivers, lakes, and ponds is unfit for use by human beings.
Q2. Seas are formed when the water table meets the land surface.
Q3. The evaporation of water takes place only in sunlight.
Q4. Condensation results in the formation of dew on the grass.
Q5. Seawater can be used for irrigation as such.
Additional True or False
Q6. Mountains help to regulate the temperature of our earth.
Q7. Solid form of water is present in underground.
Q8. Water while passing through layers of soil dissolves salt and minerals to a maximum extent.
Q9. Water freezes at 100° Celsius at normal pressure.
Q10. When the air around the clouds is cool, these drops of water fall in the form of snow or rain.
Q11. Direct collection and use of rainwater is called rainwater harvesting.
Q12. Estuaries are harmful to unique plants and animal species.
IV. Match the Following
| Column A | Column B |
|---|---|
| 1. Flood | Lake |
| 2. Surface water | Evaporation |
| 3. Sunlight | Water vapour |
| 4. Cloud | Pole |
| 5. Frozen water |
| Column A | Column B |
|---|---|
| 1. Flood | Increased rainfall |
| 2. Surface water | Lake |
| 3. Sunlight | Evaporation |
| 4. Cloud | Water vapour |
| 5. Frozen water | Pole |
Floods are caused by increased rainfall. Lakes are a source of surface water. Sunlight drives evaporation. Clouds are formed from water vapour. Frozen water (ice) is found at the poles.
V. Arrange in Correct Sequence (Water Cycle)
Arrange the following statements about the water cycle in the correct order:
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 fall as rain. 5. Water vapour is also continuously added to the atmosphere through transpiration from 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 dust particles form clouds.
Correct Sequence: 3 → 5 → 7 → 1 → 8 → 6 → 2 → 4
| Step | Statement |
|---|---|
| 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 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 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 fall as rain. |
This sequence follows: Evaporation + Transpiration → Cooling → Condensation → Cloud formation → Rising air → Droplet merging → Precipitation.
VI. Analogy
Q1. Population explosion : Water scarcity :: Recycle : \_\_\_\_\_
Just as population explosion causes water scarcity, recycling is a method of water management.
Q2. Groundwater : \_\_\_\_\_ :: Surface water : Lakes
Just as lakes are a source of surface water, tube wells are a source of groundwater.
Q3. Iceberg : Solid form :: Water vapour : \_\_\_\_\_
Iceberg is water in solid form; water vapour is water in gaseous form.
Q4. Contain more than 3% of salt : \_\_\_\_\_ :: Upto 3% of salt dissolved : Brackish water
Seawater contains more than 3% dissolved salts; brackish water contains up to 3%.
Q5. Water bodies meet the sea : Estuaries :: Wetlands : \_\_\_\_\_
Estuaries form where freshwater meets the sea; swamps are a type of wetland.
Q6. Napier Bridge area : \_\_\_\_\_ :: Pallikkaranai : Wetland
The Napier Bridge area in Chennai is an estuarine ecosystem, just as Pallikkaranai is a wetland.
VII. Very Short Answer Questions
Q1. Name four different sources of water.
Q2. How do people in cities and rural areas get water for various purposes?
Q3. Take out a cooled bottle of water from the refrigerator and keep it on a table. After some time you notice a puddle of water around it. Why?
Q4. We could see clouds almost every day. Why doesn't it rain daily?
Q5. Name the places where water is found as ice.
Q6. How do aquatic animals manage to live in the Arctic and Antarctic Circle?
Q7. What are the types of rainwater harvesting?
1. Collecting water from where it falls — e.g., collecting rainwater from rooftops (roof water harvesting). 2. Collecting flowing rainwater — e.g., constructing ponds with bunds to capture runoff.
VIII. Short Answer Questions
Q1. Differentiate between surface water and groundwater.
| Feature | Surface Water | Groundwater |
|---|---|---|
| Location | On the earth's surface | Beneath the earth's surface |
| Examples | Rivers, lakes, ponds, streams | Open wells, tube wells, hand pumps, springs |
| Accessibility | Directly visible and accessible | Requires wells, pumps, or boreholes |
Q2. Write a few slogans on "Save Water".
1. Conserve water, conserve life. 2. Save water, and it will save you. 3. It takes a lot of blues to stay green. 4. Don't let life slip down the drain. 5. Don't flush our planet's most valuable resource.
Q3. About 71% of the earth's surface is covered with water, then why do we face scarcity of water?
Q4. Give a reason — Sewage should not be disposed of in rivers or oceans before treatment.
Q5. The freshwater available on earth is only 3%. We cannot increase the amount of water. How can we sustain the water level?
1. Creating awareness about water conservation. 2. Recycling and reusing water wherever possible. 3. Minimising the use of chemical fertilisers that pollute groundwater. 4. Controlling deforestation to maintain the water cycle. 5. Adopting drip and sprinkler irrigation in agriculture. 6. Practising rainwater harvesting to recharge groundwater.
Q6. Give the uses of water.
Q7. What are the three forms of water?
Q8. Which places have freshwater?
Q9. How is 3% of freshwater distributed?
| Source | Percentage |
|---|---|
| Polar ice caps and glaciers | 68.7% |
| Groundwater | 30.1% |
| Other sources of water | 0.9% |
| Surface water | 0.3% |
Of the tiny 0.3% surface water: lakes hold 87%, swamps 11%, and rivers just 2%.
Q10. Define saline water.
Q11. How is water classified based on its salinity?
| Type | Salinity |
|---|---|
| Freshwater | 0.05% to 1% dissolved salts |
| Brackish water | Up to 3% dissolved salts |
| Seawater | More than 3% dissolved salts |
Q12. What are the salts dissolved in seawater?
Q13. Define water cycle.
Q14. What is condensation?
Q15. What is transpiration?
Q16. What is frozen water?
Q17. Define scarcity of water.
Q18. List the wetlands in Tamil Nadu.
1. Pichavaram Mangroves near Chidambaram 2. Muthupet Mangrove wetland 3. Pallikkaranai wetland in Chennai 4. Chembarambakkam in Kancheepuram
Q19. What is meant by conservation of water?
IX. Detailed / Long Answer Questions
Q1. What is potable water? List down its characteristics.
Characteristics of potable water:
1. Free from harmful contaminants — It is cleaned of disease-causing bacteria and harmful substances. 2. Transparent — Clear and free from suspended particles. 3. Odourless and colourless — Does not have any smell or colour. 4. Free from disease-causing microorganisms — Harmless and safe for consumption.
Water that lacks even one of these characteristics may not be safe to drink and requires treatment.
Q2. Who is known as the 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.
His contributions:
- Built over 8,600 johads (traditional rainwater storage tanks) to collect rainwater for year-round use.
- Brought water back to over 1,000 villages in arid Rajasthan.
- Revived five rivers in Rajasthan — Arvari, Ruparel, Sarsa, Bhagani, and Jahajwali.
- His methods focused on community-driven, low-cost water harvesting techniques like check dams and johads.
Awards received:
- Stockholm Water Prize (2005) — Often called "The Nobel Prize for Water."
- Ramon Magsaysay Award (2001) — For community leadership in water management.
- Jamnalal Bajaj Award (2005) — For constructive work.
Dr. Rajendra Singh's work demonstrates that traditional water harvesting methods, combined with community participation, can reverse desertification and revive entire river systems.
Q3. What is rainwater harvesting? Explain how it can be used in houses.
Methods of rainwater harvesting:
| Type | Description | Example |
|---|---|---|
| Roof water harvesting | Collecting rainwater from where it falls | Collecting water from rooftops into storage tanks |
| Flowing rainwater collection | Collecting rainwater that flows on the ground | Constructing ponds with bunds to capture runoff |
How it can be used in houses:
1. Rooftop collection — Rainwater falling on the roof is channelled through pipes into a storage tank or recharge pit. 2. Filtration — A simple mesh or sand filter removes leaves and debris before storage. 3. Storage — Water is stored in tanks for direct use (gardening, washing, toilet flushing). 4. Groundwater recharge — Excess water is directed into bore wells or percolation pits to recharge the groundwater table.
Benefits:
- Easy to install, operate, and maintain for all types of houses.
- Excellent source of water in emergencies.
- Reduces rainwater runoff and solves drainage problems.
- Increases the groundwater level.
Q4. Draw and describe the total water on earth by a pie chart.
| Category | Percentage |
|---|---|
| Saline water (seas and oceans) | 97% |
| Freshwater | 3% |
Distribution of 3% freshwater:
| Source | Percentage of freshwater |
|---|---|
| Polar ice caps and glaciers | 68.7% |
| Groundwater | 30.1% |
| Other sources | 0.9% |
| Surface water | 0.3% |
Distribution of 0.3% surface water:
| Source | Percentage of surface water |
|---|---|
| Lakes | 87% |
| Swamps | 11% |
| Rivers | 2% |
This shows that an extremely small fraction (just 0.3% of 3%, i.e., about 0.009% of total water) is readily available surface freshwater — making conservation essential.
Q5. What are the methods of water conservation? Explain.
Q6. Give the importance of water.
1. Body functions — Water regulates body temperature, aids digestion, and removes toxins. The body needs 3–4 litres per day. 2. Domestic use — Used for cooking, bathing, washing clothes, and cleaning. 3. Agriculture — Essential for healthy growth of crops and livestock. 4. Industry — Used in manufacturing processes at all levels of production. 5. Ecosystem — Supports aquatic life, maintains biodiversity, and sustains wetlands and forests. 6. Climate regulation — Water bodies help moderate temperature and maintain weather patterns.
Q7. What are the reasons for the scarcity of water?
1. Population explosion — Increasing population demands more water for drinking, agriculture, and industry. 2. Uneven distribution of rainfall — Some regions receive excess rain while others face droughts. 3. Decline of the groundwater table — Over-extraction through bore wells depletes groundwater faster than it can recharge. 4. Pollution of water — Industrial effluents, sewage, and chemical runoff make available water unusable. 5. Careless use of water — Wastage through leaking taps, over-irrigation, and unnecessary use depletes resources.
X. Higher Order Thinking Skills (HOTS)
Q1. When there is no pond or lake in an area, will there be the formation of clouds possible in that area?
Q2. To clean spectacles, people often breathe out on glasses to make them wet. Explain why the glasses become wet.
XI. Crossword Answers
| Direction | Clue | Answer |
|---|---|---|
| Down 1 | A method of water conservation | Recycling |
| Down 2 | Process of getting water vapour from seawater | Evaporation |
| Down 6 | Water stored in dams is used for generation of \_\_\_\_\_ | Electricity |
| Across 3 | \_\_\_\_\_ is a large body of non-potable water found in nature | Ocean |
| Across 4 | In summer, the body loses water as \_\_\_\_\_ | Sweat |
| Across 5 | Plants undergo \_\_\_\_\_ and contribute to the water cycle | Transpiration |
XII. Common Mistakes to Avoid
1. Confusing saline water percentage with freshwater. Remember: 97% of the earth's water is saline; only 3% is freshwater. Do not mix these up in exams.
2. Writing "condensation" when the answer is "evaporation" (or vice versa). Evaporation = liquid to vapour (heating). Condensation = vapour to liquid (cooling). Always check the direction of change.
3. Saying "seawater can be used for irrigation." It cannot. Seawater has more than 3% salt, which degrades soil and kills crops.
4. Confusing the freezing and boiling points. Water freezes at 0 °C and boils at 100 °C. A common error is to swap these values.
5. Stating "only 3% of water is available for drinking." The correct statement is: only 3% is freshwater, and of that, only 0.3% is readily available surface water for human consumption.
6. Listing transpiration as only "water loss." Transpiration is not merely water loss — it is a vital part of the water cycle that adds water vapour to the atmosphere and cools the plant.
7. Confusing groundwater and surface water sources. Wells, tube wells, and hand pumps draw groundwater (below surface). Rivers, lakes, and ponds are surface water (above surface).
Exam Checklist
Before your exam, make sure you can:
- [ ] Explain the water cycle (evaporation, condensation, precipitation, collection) with correct sequence
- [ ] State the distribution of water on earth (97% saline, 3% freshwater, 0.3% surface water)
- [ ] Differentiate between surface water and groundwater with examples
- [ ] Define and explain: evaporation, condensation, transpiration, precipitation
- [ ] List at least 5 methods of water conservation
- [ ] Explain rainwater harvesting and its types (roof water + flowing water collection)
- [ ] List the characteristics of potable water
- [ ] Name the three forms of water and their salinity-based classification (fresh, brackish, saline)
- [ ] Explain why cloud formation does not guarantee rain
- [ ] Identify the wetlands of Tamil Nadu (Pichavaram, Muthupet, Pallikkaranai, Chembarambakkam)
- [ ] Describe the role of Dr. Rajendra Singh (Waterman of India) and his awards
- [ ] Calculate and represent water distribution data in a pie chart
- [ ] State reasons for water scarcity (population, uneven rainfall, groundwater decline, pollution, wastage)
- [ ] Answer HOTS questions on condensation (cold bottle, breathing on glasses) and cloud formation