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NCERT Solutions for Class 6 Science Chapter 14 Water | KalviGavani

NCERT Class 6 Science Chapter 14 Water exercise solutions — water cycle evaporation condensation precipitation sources of water drought flood conservation step-by-step answers.

Updated 16 June 202619 min read

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NCERT Solutions for Class 6 Science Chapter 14 — Water

Key Concepts

TermDefinition
Water cycleThe continuous circulation of water between the Earth's surface and the atmosphere through evaporation, condensation, and precipitation.
EvaporationThe process by which water changes from liquid to vapour (gas) due to heat from the sun.
CondensationThe process by which water vapour cools and changes back into liquid water droplets, forming clouds.
PrecipitationThe falling of water from clouds to the Earth's surface in the form of rain, snow, hail, or sleet.
TranspirationThe process by which plants release water vapour into the atmosphere through their leaves.
DroughtA condition caused by very little or no rainfall over a long period, leading to water scarcity and dry conditions.
FloodA condition caused by excessive rainfall, resulting in overflowing of rivers and submerging of low-lying areas.
GroundwaterWater that seeps below the ground surface and collects in porous rocks and soil, accessed through wells and tube wells.
Water conservationThe practice of using water wisely and preventing its wastage to ensure availability for future use.
InfiltrationThe process by which rainwater seeps into the ground and replenishes the groundwater table.

Intext Questions (Page-by-Page)

Question 1: Boojho wonders whether the water in the puddle will disappear even if the sun is not shining.
AnswerYes, the water in the puddle will still disappear even without direct sunlight, but it will take a longer time. Evaporation can occur even without the sun's direct heat because it depends on temperature, wind, and surface area. On a cloudy day or even at night, the surrounding air temperature is still sufficient to cause slow evaporation. However, the rate of evaporation is much faster in direct sunlight because the sun provides the heat energy needed for water to change from liquid to vapour.
Question 2: Paheli wants to know why puddles of water dry up even in the shade.
AnswerPuddles dry up in the shade because evaporation occurs at all temperatures, not just at high temperatures. Even in the shade, the surrounding air has some heat energy that causes water molecules at the surface to gain enough energy to escape into the air as water vapour. Factors that help evaporation in the shade include:
  • Wind carries away water vapour from the surface, allowing more evaporation.
  • Low humidity in the air allows more water to evaporate.
  • Temperature of the air, even in shade, provides energy for evaporation.
  • Surface area of the water exposed to air.

However, the rate of evaporation is slower in the shade compared to direct sunlight.

Question 3: Boojho asks — can water evaporate from leaves of plants?
AnswerYes, water evaporates from the leaves of plants through a process called transpiration. Plants absorb water from the soil through their roots. This water travels up through the stem to the leaves. The leaves have tiny pores called stomata on their surfaces. Excess water is released from these stomata as water vapour into the atmosphere. Transpiration is an important part of the water cycle and contributes significantly to the amount of water vapour in the air. A single large tree can transpire hundreds of litres of water per day.
Question 4: Paheli wants to know why clouds appear to float in the sky.
AnswerClouds appear to float because the water droplets and ice crystals that make up clouds are very tiny and lightweight. These tiny droplets are so small that the upward air currents (warm air rising from the ground) are strong enough to keep them suspended in the atmosphere. The droplets are typically about 0.01 mm in diameter. As long as the upward air currents are stronger than the weight of the water droplets, the cloud remains floating. When the droplets grow larger and heavier — by combining with other droplets — they can no longer be held up by the air currents and fall down as rain.
Question 5: Boojho wants to know why it rains only in certain places and not everywhere at the same time.
AnswerRain does not occur everywhere at the same time because several conditions must be met for rainfall:

1. Availability of water vapour: There must be enough moisture in the air from evaporation from nearby water bodies. 2. Rising air currents: Warm air must rise carrying the moist air upwards. 3. Cooling: The rising air must cool enough for condensation to occur and form clouds. 4. Condensation nuclei: Tiny particles like dust, smoke, and salt in the air provide surfaces for water vapour to condense upon. 5. Sufficient accumulation: Enough water droplets must collect in the clouds to become heavy enough to fall as rain.

These conditions vary from place to place depending on geography, temperature, wind patterns, and proximity to water bodies. That is why some places get rain while others remain dry at the same time.

Question 6: Paheli noticed that the water level in a glass left on the table decreased after a few days. Where did the water go?
AnswerThe water from the glass evaporated into the air. Evaporation is a continuous process that occurs at room temperature. The water molecules at the surface gained enough energy from the surrounding air to escape into the atmosphere as water vapour. Over several days, more and more water molecules left the surface, causing the water level to decrease. This is the same process that causes puddles to dry up and wet clothes to dry on a clothesline.

Exercise Questions (NCERT Textbook)

Question 1: Fill in the blanks
Answer

(a) The process by which water changes from liquid to vapour is called ________.

AnswerThe process by which water changes from liquid to vapour is called evaporation.

(b) The process by which water vapour changes back to liquid is called ________.

AnswerThe process by which water vapour changes back to liquid is called condensation.

(c) The water that falls from clouds is called ________.

AnswerThe water that falls from clouds is called precipitation (or rain/snow/hail).

(d) Water in the form of vapour is called ________.

AnswerWater in the form of vapour is called water vapour (or steam).
Question 2: State whether the following statements are True or False
Answer

(a) Water vapour is present in air only during the monsoon season.

AnswerFalse. Water vapour is present in the air at all times, not just during the monsoon season. Even on a dry summer day or a cold winter day, there is some water vapour in the air. The amount may vary — it is higher during monsoon and lower in dry seasons — but it is never zero.

(b) Water evaporates only from large water bodies like lakes and oceans.

AnswerFalse. Water evaporates from all sources — lakes, oceans, rivers, ponds, puddles, wet clothes, soil, and even from plants (transpiration). Any exposed water surface can undergo evaporation.

(c) Condensation is the reverse of evaporation.

AnswerTrue. Evaporation is the process of water changing from liquid to vapour, and condensation is the reverse process of water vapour changing back to liquid. They are opposite processes.

(d) Rain is the only form of precipitation.

AnswerFalse. Rain is one form of precipitation, but not the only one. Other forms of precipitation include snow, hail, and sleet. The form of precipitation depends on the temperature at which condensation occurs and the temperature through which the precipitation falls.
Question 3: Which of the following is NOT a source of water?
Answer

(a) Rivers ✓ Glaciers (c) Rain (d) All are sources

Answer(b) Glaciers are not directly a source of water in the sense of daily use, though they feed rivers. However, all the listed options — rivers, glaciers, and rain — are sources of water in the broader sense. The most common NCERT answer expected is that all are sources, so the best answer is (b) Glaciers if the question treats glaciers as indirect sources. But in reality, all are sources. The key point is that rain is the primary source of all fresh water on Earth.
Question 4: Describe the water cycle in detail.
AnswerThe water cycle (also called the hydrological cycle) is the continuous movement of water from the Earth's surface to the atmosphere and back again. It involves the following stages:

1. Evaporation: The sun heats water in oceans, rivers, lakes, ponds, and other water bodies. This heat energy causes water to change from liquid to water vapour. Water vapour rises into the atmosphere. Plants also release water vapour through transpiration.

2. Condensation: As the water vapour rises, it encounters cooler temperatures at higher altitudes. The water vapour cools and condenses into tiny water droplets or ice crystals. These tiny droplets cluster around dust particles and other tiny particles in the air to form clouds and fog.

3. Precipitation: When the water droplets in the clouds combine and become too heavy to remain suspended in the air, they fall back to the Earth's surface as precipitation — rain, snow, hail, or sleet. The type of precipitation depends on the temperature.

4. Collection/Run-off: The water that falls on the ground collects in rivers, lakes, and ponds (surface run-off) or seeps into the ground (infiltration) to recharge groundwater. This water eventually flows back to oceans and seas, and the cycle begins again.

The water cycle is a continuous and never-ending process. It maintains a balance of water on Earth and ensures that fresh water is constantly being recycled and redistributed.

Question 5: What are the different sources of water? Explain each.
AnswerThe different sources of water are:

1. Rain: Rain is the primary and most important source of fresh water on Earth. All other sources of water are directly or indirectly dependent on rainfall. Rainwater fills rivers, lakes, and ponds, and also seeps into the ground to form groundwater.

2. Rivers: Rivers are flowing bodies of water that originate from mountains (from glaciers, springs, or rainfall) and flow towards the sea. They are a major source of water for drinking, irrigation, and industries. Examples: Ganga, Yamuna, Brahmaputra.

3. Lakes and Ponds: These are still bodies of water. Lakes are larger than ponds. They collect rainwater and water from small streams. They are used for drinking water supply, irrigation, and fishing.

4. Groundwater: Rainwater that seeps into the ground collects in porous rocks and soil layers. This underground water is called groundwater. It is accessed through wells, hand pumps, and tube wells. Groundwater is a very important source of water, especially in areas where surface water is scarce.

5. Wells, Hand Pumps, and Tube Wells: These are man-made structures used to draw groundwater to the surface. Wells are dug into the ground to reach the water table. Hand pumps and tube wells are used to pump groundwater to the surface.

6. Glaciers and Ice Caps: In mountainous and polar regions, water is stored in the form of ice and snow. When this ice melts, it feeds rivers and streams. The Himalayan glaciers are the source of many major rivers in India.

7. Seas and Oceans: These contain salt water (not fit for drinking) but are the largest reservoirs of water on Earth. They play a crucial role in the water cycle by providing water vapour through evaporation.

Question 6: What is drought? What are its effects?
AnswerA drought is a condition that occurs when there is very little or no rainfall in a region for a long period of time (months or even years). This leads to a severe shortage of water.

Effects of drought:

1. Water scarcity: Rivers, lakes, ponds, and wells dry up. There is not enough water for drinking, bathing, cooking, and other daily needs.

2. Crop failure: Without sufficient rain, crops cannot grow. Farmers face huge losses as their fields dry up. This leads to food shortage.

3. Famine: Prolonged drought leads to famine — a condition where there is not enough food for the population, leading to hunger and malnutrition.

4. Loss of vegetation: Plants and trees dry up and die due to lack of water. Forests and grasslands are destroyed.

5. Soil erosion: Without vegetation to hold the soil, the dry soil becomes loose and is easily blown away by wind (wind erosion).

6. Migration: People and animals are forced to migrate from drought-affected areas to places where water and food are available.

7. Economic hardship: Farmers lose their income, leading to poverty. The entire economy of the region is affected.

8. Groundwater depletion: People draw more and more groundwater, leading to a fall in the water table.

Question 7: What is flood? What are its effects?
AnswerA flood is a condition that occurs when there is excessive rainfall in a region, causing rivers and lakes to overflow their banks and submerge the surrounding land.

Effects of flood:

1. Destruction of property: Floodwaters damage houses, roads, bridges, and other infrastructure. People lose their homes and belongings.

2. Crop damage: Standing crops in fields are submerged and destroyed. This leads to significant financial losses for farmers.

3. Loss of life: Floods can cause drowning, electrocution, and other accidents. Many people and animals lose their lives.

4. Waterborne diseases: Floodwater mixes with sewage and contaminates drinking water sources. This leads to the spread of diseases like cholera, typhoid, dysentery, and malaria.

5. Soil erosion: Fast-flowing floodwater washes away the fertile top layer of soil, reducing agricultural productivity.

6. Displacement: People are forced to leave their homes and take shelter in relief camps.

7. Damage to infrastructure: Roads, railways, power lines, and communication networks are disrupted.

8. Animal and livestock loss: Domestic animals and wildlife are also affected. Many animals drown or are stranded without food.

Question 8: Why is water conservation important? List some methods of water conservation.
AnswerWater conservation is important because:

1. Limited fresh water: Only about 1% of all the water on Earth is available as fresh water for human use. The rest is salt water (in oceans) or frozen (in glaciers).

2. Growing population: The increasing population means more demand for water for drinking, agriculture, and industries.

3. Irregular rainfall: Due to climate change, rainfall patterns are becoming unpredictable, making water availability uncertain.

4. Depletion of groundwater: Excessive use of groundwater is causing the water table to fall in many regions.

5. Future generations: We must conserve water to ensure that future generations also have access to clean water.

Methods of water conservation:

1. Rainwater harvesting: Collecting and storing rainwater for future use. Rainwater is collected from rooftops and stored in tanks or allowed to seep into the ground to recharge groundwater.

2. Drip irrigation: A method of watering plants where water is delivered directly to the roots drop by drop. This reduces water wastage significantly compared to traditional flood irrigation.

3. Turning off taps: Not letting taps run while brushing teeth, washing dishes, or bathing.

4. Repairing leaks: Fixing leaking taps and pipes immediately. A dripping tap can waste thousands of litres of water per year.

5. Using water-efficient appliances: Using washing machines and dishwashers only with full loads.

6. Reusing water: Using wastewater from washing vegetables to water plants.

7. Afforestation: Planting more trees helps increase rainfall and reduces soil erosion, which helps conserve water.

8. Check dams and bunds: Building small dams and bunds on rivers and streams to slow down water flow and allow more water to seep into the ground.

Question 9: How are clouds formed?
AnswerClouds are formed through the process of condensation. The process occurs as follows:

1. Evaporation: Water from oceans, rivers, lakes, ponds, and other water bodies evaporates due to the heat of the sun. Plants also release water vapour through transpiration. This water vapour rises into the atmosphere.

2. Rising and cooling: As the water vapour rises, it reaches higher altitudes where the temperature is lower. The warm moist air rises because it is lighter than the surrounding cooler air.

3. Condensation: At higher altitudes, the air temperature drops. When the water vapour cools down, it condenses (changes from gas to liquid) and forms tiny water droplets. These tiny droplets need surfaces to condense on — they condense around tiny particles of dust, smoke, and salt present in the air. These particles are called condensation nuclei.

4. Cloud formation: Millions of these tiny water droplets (and sometimes ice crystals at very high altitudes) come together and float in the atmosphere, forming what we see as clouds. The upward air currents keep these tiny droplets suspended, making clouds appear to float in the sky.

Question 10: Explain how the water from the ocean reaches back to the ocean.
AnswerThe water from the ocean reaches back to the ocean through the water cycle, which is a continuous process:

1. Evaporation: The sun heats the water in the oceans. Water evaporates and rises into the atmosphere as water vapour. Since oceans cover about 71% of the Earth's surface, they are the largest source of water vapour.

2. Condensation and cloud formation: The water vapour rises, cools at higher altitudes, and condenses to form clouds.

3. Precipitation: When the water droplets in clouds become heavy enough, they fall back to the Earth's surface as rain, snow, hail, or sleet.

4. Run-off and collection: The rainwater that falls on land collects in rivers, streams, and lakes. Some of it seeps into the ground to recharge groundwater. The rivers and streams carry the water back to the oceans.

5. Return to ocean: All the rivers and streams eventually flow back into the oceans. Even groundwater slowly moves through rocks and soil towards the oceans.

Thus, the water that evaporated from the oceans returns to the oceans, completing the cycle. This is why the total amount of water on Earth remains roughly constant — water is continuously being recycled through the water cycle.

Multiple Choice Questions (MCQs)

1. Which process converts water from liquid to vapour?
Answer

(a) Condensation ✓ Evaporation (c) Precipitation (d) Freezing

Answer(b) Evaporation. Evaporation is the process by which water changes from liquid to vapour.
2. The primary source of fresh water on Earth is:
Answer

(a) Rivers ✓ Rain (c) Groundwater (d) Lakes

Answer(b) Rain. Rain is the primary source of fresh water. All other sources are fed by rainfall.
3. Which of the following increases the rate of evaporation?
Answer

(a) Decreasing temperature ✓ Increasing surface area (c) High humidity (d) All of these

Answer(b) Increasing surface area. A larger surface area allows more water molecules to escape into the air, increasing evaporation.
4. What happens when water vapour comes in contact with a cold surface?
Answer

(a) It evaporates ✓ It condenses (c) It freezes immediately (d) Nothing happens

Answer(b) It condenses. When water vapour comes in contact with a cold surface, it loses heat and condenses into liquid water droplets.
5. Which of the following is a consequence of drought?
Answer

(a) Overflowing rivers ✓ Crop failure (c) Waterlogging (d) Flooding of fields

Answer(b) Crop failure. Drought causes water scarcity which leads to crop failure due to lack of water for irrigation.

Common Mistakes

1. Confusing evaporation and boiling: Evaporation occurs at all temperatures and only at the surface of a liquid. Boiling occurs at a specific temperature (100 degrees Celsius for water at normal pressure) and throughout the liquid. Students often use these terms interchangeably, which is incorrect.

2. Thinking condensation only happens in clouds: Condensation can happen anywhere water vapour meets a cold surface. The water droplets on the outside of a cold glass, morning dew on grass, and fog on windows are all examples of condensation, not just cloud formation.

3. Believing groundwater is an unlimited resource: Many students think the water table will never run dry. In reality, excessive pumping of groundwater (more than what gets recharged by rain) causes the water table to fall. Groundwater is a finite resource that can be depleted.

4. Confusing drought and flood causes and effects: Drought is caused by too little rain; flood is caused by too much rain. Their effects are opposite — drought causes dryness and water scarcity, while flood causes excess water and submergence. Students sometimes mix up the two.

5. Ignoring transpiration as part of the water cycle: Students often focus only on evaporation from water bodies and forget that plants release significant amounts of water vapour through transpiration. Transpiration is an important part of the water cycle and contributes a large portion of atmospheric moisture.

Exam Checklist

  • [ ] I can define the water cycle and describe its four main stages: evaporation, condensation, precipitation, and collection.
  • [ ] I can explain the difference between evaporation and condensation with examples from daily life.
  • [ ] I can list the various sources of water and explain the importance of rain as the primary source.
  • [ ] I can describe how clouds are formed through the process of condensation.
  • [ ] I can explain what drought and flood are, their causes, and their effects on life and the environment.
  • [ ] I can list at least five methods of water conservation and explain why conserving water is important.
  • [ ] I can explain transpiration and its role in the water cycle.
  • [ ] I can describe how water from oceans returns to oceans through the water cycle.

Frequently Asked Questions

The water cycle is the continuous process by which water circulates between the Earth's surface and the atmosphere. Water evaporates from water bodies, forms clouds by condensation, falls back as rain/snow (precipitation), and flows back to water bodies. This cycle goes on continuously.