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Chapter 8. A Journey through States of Water

Chapter Review

Chapter 8. A Journey through States of Water

Water is one of the most important natural resources on Earth. It exists in three different states—solid, liquid, and gas. This chapter explains how water changes from one state to another through heating and cooling, the processes of evaporation and condensation, the cooling effect of evaporation, cloud formation, and the water cycle. These chapter review notes are prepared for quick revision according to the latest NCERT Curiosity textbook and CBSE pattern.

Chapter Review

This chapter review provides a quick summary of all the important concepts, definitions, properties, scientific terms, and applications covered in the chapter. It is useful for last-minute revision and examination preparation.

Introduction

Water is essential for all living organisms. It is the only common substance that naturally exists in three physical states—solid (ice), liquid (water), and gas (water vapour). These states continuously change into one another due to heating and cooling, making water an important part of many natural processes such as rainfall and the water cycle.

What are the States of Water?

Water exists in three different physical states. Although their appearance and properties are different, all three are forms of the same substance.

State	Example	Main Characteristic
Solid	Ice	Fixed shape and fixed volume
Liquid	Water	Fixed volume but no fixed shape
Gas	Water Vapour	No fixed shape and no fixed volume

Properties of Different States of Water

Each state of water has its own unique properties that help us identify and distinguish it from the others.

Property	Ice	Water	Water Vapour
Shape	Fixed	Takes the shape of the container	No fixed shape
Volume	Fixed	Fixed	No fixed volume
Flows	No	Yes	Yes
Spreads	No	Very little	Spreads in all directions

Important Definitions

The following definitions are frequently asked in school examinations and should be remembered carefully.

Term	Definition
Evaporation	The process of changing liquid water into water vapour.
Condensation	The process of changing water vapour into liquid water.
Melting	The conversion of a solid into a liquid on heating.
Freezing	The conversion of a liquid into a solid on cooling.
Humidity	The amount of water vapour present in the air.
Water Cycle	The continuous movement of water between the Earth's surface and the atmosphere.

Changes of State

Water changes from one state to another when heat is supplied or removed.

Process	Change	Cause
Melting	Solid → Liquid	Heating
Evaporation	Liquid → Gas	Heating or room temperature
Condensation	Gas → Liquid	Cooling
Freezing	Liquid → Solid	Cooling

Factors Affecting Evaporation

Evaporation takes place continuously, but its speed depends upon different environmental conditions.

Factor	Effect
High Temperature	Increases evaporation.
Large Surface Area	Increases evaporation.
Wind Speed	Increases evaporation.
High Humidity	Decreases evaporation.

Cooling Effect of Evaporation

During evaporation, water absorbs heat from its surroundings before changing into water vapour. As heat is removed, the surrounding surface becomes cooler.

Examples:

• Sweating cools our body.
• Water remains cool in an earthen pot (matka).
• Hand sanitiser produces a cooling sensation.
• Sprinkling water on the floor during summer cools the surroundings.

Condensation in Daily Life

Condensation occurs when water vapour comes in contact with a cold surface and changes back into liquid water.

Examples:

• Water droplets on a cold glass.
• Dew drops on grass.
• Water droplets on the lid of a boiling vessel.
• Fog on mirrors after a hot bath.

Cloud Formation

Water vapour rises into the atmosphere due to evaporation. At higher altitudes, the air becomes cooler. Water vapour condenses around tiny dust particles to form clouds. When water droplets become heavy, they fall as rain, snow, or hail.

Water Cycle

The water cycle is the continuous circulation of water in nature. It ensures that water keeps moving between the Earth's surface and the atmosphere.

Stage	Description
Evaporation	Water changes into water vapour.
Condensation	Clouds are formed.
Precipitation	Rain, snow, or hail falls on the Earth.
Collection	Water collects in rivers, lakes, oceans, and groundwater.

Applications

The concepts of this chapter are useful in everyday life as well as in science.

• Drying of clothes.
• Preparation of common salt from seawater.
• Cooling of the human body by sweating.
• Storage of cool water in earthen pots.
• Formation of clouds and rainfall.
• Food preservation using pot coolers.
• Weather forecasting.
• Understanding the natural water cycle.

Important Terms

Remember the following scientific terms for quick revision.

Scientific Term	Meaning
Solid	State having fixed shape and fixed volume.
Liquid	State having fixed volume but no fixed shape.
Gas	State having neither fixed shape nor fixed volume.
Water Vapour	Invisible gaseous form of water.
Humidity	Water vapour present in air.
Melting	Solid changes into liquid.
Freezing	Liquid changes into solid.
Evaporation	Liquid changes into gas.
Condensation	Gas changes into liquid.
Water Cycle	Continuous movement of water in nature.

Chapter Highlights

The following points summarise the complete chapter for quick revision.

• Water exists in solid, liquid, and gaseous states.
• Ice, water, and water vapour are forms of the same substance.
• Heating and cooling change the state of water.
• Melting converts solid into liquid.
• Freezing converts liquid into solid.
• Evaporation occurs even at room temperature.
• Condensation forms water droplets from water vapour.
• Temperature, wind, humidity, and surface area affect evaporation.
• Evaporation produces a cooling effect.
• Clouds are formed due to condensation.
• Rain is a result of condensation and precipitation.
• The water cycle maintains the continuous movement of water on Earth.
• Scientific observation and experimentation help us understand natural phenomena.
• Water is a precious natural resource and should be used wisely.

Chapter 8. A Journey through States of Water

NCERT TextBook Questions With Answers

Chapter 8. A Journey through States of Water

The following NCERT textbook exercise is prepared according to the latest NCERT Curiosity textbook and CBSE pattern. Each answer is written in simple, original, and student-friendly language to help learners understand the concepts clearly while preparing for school examinations.

NCERT Textbook Exercise

Read each question carefully before answering. Wherever required, suitable explanations have been provided to improve conceptual understanding.

Question 1. Which of the following best describes condensation?

(A) The conversion of water into its vapour state.
(B) The process of water changing from a liquid into gaseous state.
(C) The formation of clouds from tiny water droplets.
(D) The conversion of water vapour into its liquid state.

Answer: (D) The conversion of water vapour into its liquid state.

Explanation: Condensation is the process in which water vapour loses heat and changes back into liquid water. This process is responsible for the formation of dew, water droplets on a cold glass, and clouds. :contentReference[oaicite:0]{index=0}

Question 2. Identify in which of the following processes evaporation is very important.

(i) Colouring with

(A) Crayons
(B) Water colours
(C) Acrylic colours
(D) Pencil colours

Answer: (B) Water colours

Explanation: Water colours dry because the water present in them evaporates, leaving the coloured pigment on the paper.

(ii) Writing on paper with

(A) Pencil
(B) Ink pen
(C) Ball point pen

Answer: (B) Ink pen

Explanation: The liquid ink dries after the solvent evaporates, making evaporation an important part of writing with an ink pen. :contentReference[oaicite:1]{index=1}

Question 3. We see green coloured plastic grass at many places these days. Space around natural grass feels cooler than the space around plastic grass. Can you find out why?

Answer:

Natural grass contains water. Water continuously evaporates from the leaves through transpiration and evaporation. During evaporation, heat is absorbed from the surroundings, producing a cooling effect. Plastic grass does not contain water and therefore cannot produce this cooling effect. As a result, the area around natural grass feels cooler than the area around artificial grass.

Question 4. Give examples of liquids other than water that evaporate.

Answer:

Some common liquids that evaporate are:

• Hand sanitiser
• Perfume
• Petrol
• Alcohol
• Nail polish remover (acetone)

Explanation: These liquids change into vapour when exposed to air. Some of them evaporate much faster than water.

Question 5. Fans move air around, creating a cooling sensation. It might seem strange to use a fan to dry wet clothes since fans usually make things cooler, not warmer. Normally, when water evaporates, it requires heat, not cold air. What do you think about this?

Answer:

A fan increases the movement of air around wet clothes. Moving air removes the water vapour formed during evaporation, allowing more water to evaporate quickly. Although the air from the fan is not hot, it increases the rate of evaporation. Therefore, clothes dry faster under a fan.

Explanation:

• Moving air increases evaporation.
• Faster evaporation removes moisture quickly.
• Hence, wet clothes dry faster even without heating.

Question 6. Usually, when sludge is removed from drains, it is left in heaps next to the drain for 3–4 days. Afterward, it is transported to a garden or a field where it can be used as manure. This approach reduces transportation cost of the sludge and enhances the safety of individuals handling it. Reflect upon it and explain how.

Answer:

Fresh sludge contains a large amount of water, making it heavy and difficult to transport. When it is left in heaps for a few days, much of the water evaporates naturally. As the moisture content decreases, the sludge becomes lighter, easier to handle, and less likely to spread dirty water. This reduces transportation costs and improves the safety and convenience of workers handling the sludge.

Question 7. Observe the activities in your house for a day. Identify the activities that involve evaporation. How does understanding the process of evaporation help us in our daily activities?

Answer:

Activities involving evaporation:

• Drying washed clothes.
• Drying of mopped floors.
• Cooling of the body through sweating.
• Drying utensils after washing.
• Drying of wet bathrooms.

Importance of evaporation:

• Helps in drying clothes quickly.
• Keeps our body cool through sweating.
• Helps preserve food in earthen pot coolers.
• Explains why fans help dry wet surfaces faster.

Question 8. How is water present in the solid state in nature?

Answer:

In nature, water is present in the solid state as:

• Snow
• Ice
• Glaciers
• Icebergs
• Frozen lakes and rivers in very cold regions

Question 9. Reflect on the statement, "Water is our responsibility before it is our right." Share your thoughts.

Answer:

Water is one of the most valuable natural resources. Every person has the responsibility to use water wisely, prevent wastage, and keep rivers, lakes, and ponds free from pollution. Conserving water today will ensure that future generations also have access to clean and sufficient water. Responsible use of water is therefore more important than simply considering it our right.

Question 10. The seat of a two-wheeler parked on a sunny day has become very hot. How can you cool it down?

Answer:

The hot seat can be cooled by sprinkling a small amount of water on it. As the water evaporates, it absorbs heat from the seat, producing a cooling effect. Keeping the vehicle in the shade or covering the seat also helps reduce its temperature.

Explanation: This cooling takes place because evaporation absorbs heat from the surroundings before water changes into water vapour.

Chapter 8. A Journey through States of Water

Extra Questions Examination Based

Chapter 8. A Journey through States of Water

The following important questions are prepared according to the latest CBSE pattern and the NCERT Curiosity textbook. These questions cover conceptual understanding, competency-based learning, and examination-oriented practice.

Important Questions with Answers

Practice these questions regularly to strengthen your understanding of the chapter and improve your performance in school examinations.

1 Mark Questions

Answer each question in one sentence.

Question 1. Name the three states in which water exists.

Answer: Water exists in solid (ice), liquid (water), and gaseous (water vapour) states.

Question 2. What is evaporation?

Answer: Evaporation is the process of changing liquid water into water vapour.

Question 3. What is condensation?

Answer: Condensation is the process in which water vapour changes into liquid water.

Question 4. What is melting?

Answer: Melting is the process of changing a solid into a liquid on heating.

Question 5. What is freezing?

Answer: Freezing is the process of changing a liquid into a solid on cooling.

Question 6. What is humidity?

Answer: Humidity is the amount of water vapour present in the air.

Question 7. Give one example of evaporation in daily life.

Answer: Drying of wet clothes is an example of evaporation.

Question 8. Why do water droplets appear on the outer surface of a cold glass?

Answer: Water vapour in the air condenses on the cold surface of the glass.

Question 9. Name one factor that increases evaporation.

Answer: High temperature increases evaporation.

Question 10. What is the water cycle?

Answer: The continuous movement of water between the Earth's surface and the atmosphere is called the water cycle.

2 Marks Questions

Answer each question in about 30–40 words.

Question 1. Differentiate between evaporation and condensation.

Answer:

Evaporation	Condensation
Liquid changes into water vapour.	Water vapour changes into liquid.
Occurs on heating or at room temperature.	Occurs on cooling.

Question 2. Why do clothes dry faster on a windy day?

Answer: Wind continuously removes water vapour from the surface of clothes, increasing the rate of evaporation. Therefore, clothes dry faster on windy days.

Question 3. Write any two examples of condensation.

Answer:

• Water droplets on a cold glass.
• Dew drops on grass in the morning.

Question 4. Mention any two uses of evaporation in daily life.

Answer:

• Drying washed clothes.
• Cooling the body through sweating.

Question 5. Why is water called a unique substance?

Answer: Water is called a unique substance because it naturally exists in all three states—solid, liquid, and gas—under normal conditions on Earth.

3 Marks Questions

Answer each question in about 50–70 words.

Question 1. Explain the three states of water.

Answer:

Water exists in three physical states. Ice is the solid state with a fixed shape and volume. Liquid water has a fixed volume but takes the shape of its container. Water vapour is the gaseous state and has neither a fixed shape nor a fixed volume. These states change into one another through heating and cooling.

Question 2. Explain the cooling effect of evaporation with suitable examples.

Answer:

During evaporation, water absorbs heat from its surroundings before changing into vapour. This removes heat and produces cooling. Sweating cools our body, water remains cool in an earthen pot, and hand sanitiser gives a cooling sensation because of evaporation.

Question 3. Describe the factors affecting evaporation.

Answer:

Evaporation becomes faster when the temperature is high, the exposed surface area is large, and air movement is greater. High humidity slows down evaporation because the air already contains a large amount of water vapour.

Question 4. Explain how clouds are formed.

Answer:

Water evaporates from rivers, lakes, and oceans. The water vapour rises into the atmosphere where the air is cooler. It condenses around tiny dust particles to form small water droplets. Millions of these droplets together form clouds.

Question 5. Explain the stages of the water cycle.

Answer:

The water cycle consists of evaporation, condensation, precipitation, and collection. Water evaporates, forms clouds through condensation, falls as rain or snow, and finally collects in rivers, lakes, oceans, and underground sources before repeating the cycle.

Long Answer Questions

Answer each question in detail.

Question 1. Explain the changes of state of water with the help of a flow diagram.

Answer:

Water changes its state when heat is supplied or removed. Heating converts ice into water and water into water vapour. Cooling changes water vapour into water and water into ice.

Heating	Cooling
Ice → Water → Water Vapour	Water Vapour → Water → Ice

These are physical changes because no new substance is formed during the process.

Question 2. Explain the process of evaporation and discuss the factors affecting it.

Answer:

Evaporation is the process by which liquid water changes into water vapour. It occurs continuously, even at room temperature. The rate of evaporation increases with higher temperature, greater surface area, and stronger air movement. It decreases when the humidity of the surrounding air is high. Evaporation is responsible for drying clothes, cooling the body through sweating, and many other everyday phenomena.

Question 3. Explain the cooling effect of evaporation with suitable examples.

Answer:

When water evaporates, it absorbs heat from the surrounding objects. This loss of heat produces a cooling effect. Sweating cools the human body because sweat evaporates from the skin. Water stored in earthen pots remains cool due to slow evaporation through tiny pores. Hand sanitisers and perfumes also produce a cooling sensation because they evaporate quickly.

Question 4. Describe the formation of clouds and rainfall.

Answer:

The Sun heats water present in rivers, lakes, ponds, and oceans. Water evaporates and rises into the atmosphere as water vapour. At higher altitudes, the air becomes cooler, causing condensation around tiny dust particles. This forms clouds. As water droplets combine and become heavier, they fall to the Earth as rain. In colder regions, precipitation may occur as snow or hail.

Question 5. Explain the importance of the water cycle.

Answer:

The water cycle continuously recycles water on Earth. It supplies fresh water to rivers, lakes, plants, animals, and human beings. It also maintains the balance of nature, supports agriculture, replenishes groundwater, and helps regulate weather and climate. Without the water cycle, life on Earth would not be possible.

Chapter 8. A Journey through States of Water

40 Important MCQs with Answers

Chapter 8. A Journey through States of Water

The following multiple-choice questions are prepared according to the latest NCERT Curiosity textbook and CBSE competency-based pattern. These questions cover conceptual understanding, application-based learning, and everyday situations related to the different states of water.

40 Important MCQs with Answer Key

Choose the most appropriate answer for each question.

1. Water naturally exists in how many physical states?

(A) One    (B) Two    (C) Three    (D) Four

2. Which of the following is the solid state of water?

(A) Steam    (B) Ice    (C) Rain    (D) Dew

3. Water vapour is the ______ state of water.

(A) Solid    (B) Liquid    (C) Gaseous    (D) Frozen

4. Which process changes ice into water?

(A) Freezing    (B) Melting    (C) Evaporation    (D) Condensation

5. Which process changes water into ice?

(A) Condensation    (B) Melting    (C) Freezing    (D) Evaporation

6. Evaporation changes water into

(A) Ice    (B) Steam or water vapour    (C) Snow    (D) Dew

7. Condensation changes water vapour into

(A) Ice    (B) Liquid water    (C) Steam    (D) Snow

8. Evaporation can occur

(A) Only at 100°C    (B) Only in summer    (C) At all temperatures    (D) Only at night

9. Which factor increases evaporation?

(A) High humidity    (B) Low temperature    (C) Strong wind    (D) Small surface area

10. Which factor slows down evaporation?

(A) High temperature    (B) Wind    (C) High humidity    (D) Large surface area

11. Clothes dry faster on a windy day because

(A) Wind cools clothes    (B) Wind increases evaporation    (C) Wind freezes water    (D) Wind removes dust

12. Water droplets on the outside of a cold glass are formed due to

(A) Melting    (B) Freezing    (C) Condensation    (D) Boiling

13. Dew drops are formed because of

(A) Evaporation    (B) Condensation    (C) Melting    (D) Boiling

14. Which process is responsible for cloud formation?

(A) Melting    (B) Freezing    (C) Condensation    (D) Filtration

15. Which process produces a cooling effect?

(A) Freezing    (B) Melting    (C) Evaporation    (D) Condensation

16. Sweating cools our body because of

(A) Condensation    (B) Freezing    (C) Evaporation    (D) Melting

17. Water remains cool in an earthen pot because of

(A) Freezing    (B) Evaporation    (C) Melting    (D) Boiling

18. Which of the following has a fixed shape?

(A) Water    (B) Water vapour    (C) Ice    (D) Steam

19. Which state has a fixed volume but no fixed shape?

(A) Solid    (B) Liquid    (C) Gas    (D) Plasma

20. Which state has neither fixed shape nor fixed volume?

(A) Solid    (B) Liquid    (C) Gas    (D) Ice

21. The gaseous form of water is called

(A) Fog    (B) Water vapour    (C) Dew    (D) Snow

22. Which of these is NOT an example of evaporation?

(A) Drying clothes    (B) Drying a floor    (C) Water droplets on a cold bottle    (D) Drying wet hair

23. Humidity means

(A) Dust in air    (B) Water vapour in air    (C) Oxygen in air    (D) Smoke in air

24. A larger surface area makes evaporation

(A) Slower    (B) Faster    (C) Stop    (D) Impossible

25. Which process requires heat?

(A) Condensation    (B) Evaporation    (C) Freezing    (D) Solidification

26. During condensation, water vapour

(A) Gains heat    (B) Loses heat    (C) Boils    (D) Freezes directly

27. Rain is a part of the

(A) Nitrogen cycle    (B) Carbon cycle    (C) Water cycle    (D) Rock cycle

28. Which stage comes after condensation in the water cycle?

(A) Evaporation    (B) Collection    (C) Precipitation    (D) Freezing

29. Which of the following is a form of precipitation?

(A) Rain    (B) Snow    (C) Hail    (D) All of these

30. The Sun provides energy mainly for

(A) Condensation    (B) Evaporation    (C) Freezing    (D) Collection

31. Which process changes water vapour into clouds?

(A) Melting    (B) Condensation    (C) Freezing    (D) Boiling

32. Which statement about water is correct?

(A) It exists only as a liquid    (B) It exists only as a solid    (C) It exists in three states    (D) It cannot change its state

33. Artificial grass feels warmer than natural grass because

(A) It evaporates more water    (B) It has no evaporation cooling effect    (C) It freezes easily    (D) It absorbs less heat

34. Which liquid evaporates faster than water?

(A) Honey    (B) Alcohol    (C) Glycerine    (D) Oil

35. Which of the following is an example of melting?

(A) Ice cream becoming liquid    (B) Water becoming ice    (C) Steam forming clouds    (D) Rainfall

36. Which process occurs when water is kept inside a freezer?

(A) Evaporation    (B) Freezing    (C) Condensation    (D) Melting

37. Which process helps in making common salt from seawater?

(A) Condensation    (B) Evaporation    (C) Freezing    (D) Melting

38. The continuous circulation of water in nature is called

(A) Carbon cycle    (B) Nitrogen cycle    (C) Water cycle    (D) Rock cycle

39. Which process changes liquid water into water vapour?

(A) Freezing    (B) Condensation    (C) Evaporation    (D) Melting

40. Which statement is correct?

(A) Water is a renewable natural resource through the water cycle.
(B) Water can exist only in liquid form.
(C) Evaporation occurs only during summer.
(D) Condensation produces heat.

Answer Key

1-C, 2-B, 3-C, 4-B, 5-C, 6-B, 7-B, 8-C, 9-C, 10-C,
11-B, 12-C, 13-B, 14-C, 15-C, 16-C, 17-B, 18-C, 19-B, 20-C,
21-B, 22-C, 23-B, 24-B, 25-B, 26-B, 27-C, 28-C, 29-D, 30-B,
31-B, 32-C, 33-B, 34-B, 35-A, 36-B, 37-B, 38-C, 39-C, 40-A.