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A Journey through States of Water

Chapter 8. A Journey through States of Water

These CBSE Notes – Key Points are prepared according to the latest NCERT Curiosity textbook and the current CBSE pattern. They provide a quick revision of important concepts, scientific terms, definitions, processes, and applications covered in the chapter.

CBSE Notes – Key Points

This section helps students revise the chapter quickly before examinations. Learn the important definitions, keywords, tables, and facts carefully for better conceptual understanding.

Important Keywords

The following keywords are frequently used in this chapter and are important from the examination point of view.

Keyword	Meaning
State of Matter	The physical form in which a substance exists.
Solid	A state having a fixed shape and fixed volume.
Liquid	A state having a fixed volume but no fixed shape.
Gas	A state having neither fixed shape nor fixed volume.
Water Vapour	The gaseous form of water.
Evaporation	Conversion of liquid water into water vapour.
Condensation	Conversion of water vapour into liquid water.
Melting	Conversion of a solid into a liquid.
Freezing	Conversion of a liquid into a solid.
Humidity	The amount of water vapour present in the air.
Water Cycle	Continuous movement of water in nature.

Important Definitions

Students should remember these definitions as they are frequently asked in one-mark and competency-based questions.

Term	Definition
Evaporation	The process by which liquid water changes into water vapour.
Condensation	The process by which water vapour changes into liquid water after cooling.
Melting	The process of changing a solid into a liquid on heating.
Freezing	The process of changing a liquid into a solid on cooling.
Water Cycle	The continuous circulation of water between the Earth's surface and the atmosphere.

States of Water

Water is one of the few substances that naturally exists in three different physical states.

State	Example	Main Property
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

Changes of State

Heating and cooling change water from one state to another. No new substance is formed during these changes.

Process	State Change	Cause
Melting	Solid → Liquid	Heating
Evaporation	Liquid → Gas	Heating or Room Temperature
Condensation	Gas → Liquid	Cooling
Freezing	Liquid → Solid	Cooling

Factors Affecting Evaporation

The rate of evaporation depends upon several environmental conditions.

Factor	Effect
High Temperature	Evaporation increases.
Large Surface Area	Evaporation increases.
High Wind Speed	Evaporation increases.
High Humidity	Evaporation decreases.

Cooling Effect of Evaporation

Evaporation absorbs heat from the surroundings, producing a cooling effect.

Examples:

• Sweating cools our body.
• Water remains cool in an earthen pot.
• Hand sanitiser produces a cooling sensation.
• Wet clothes dry with cooling.

Cloud Formation

Clouds are formed through condensation of water vapour in the atmosphere.

• Sun heats water bodies.
• Water evaporates.
• Water vapour rises.
• Cool air causes condensation.
• Tiny droplets form clouds.
• Heavy droplets fall as rain.

The Water Cycle

The water cycle continuously recycles water in nature.

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

Properties of Different States of Water

The three states of water have different physical properties.

Property	Solid	Liquid	Gas
Shape	Fixed	No fixed shape	No fixed shape
Volume	Fixed	Fixed	No fixed volume
Flow	No	Yes	Yes

Applications in Daily Life

The concepts learnt in this chapter are applied in many everyday situations.

• Drying of clothes.
• Cooling through sweating.
• Preparation of common salt from seawater.
• Storage of water in earthen pots.
• Cloud formation and rainfall.
• Food preservation using pot coolers.
• Weather forecasting.
• Understanding natural water circulation.

Important Facts

Remember these important facts for quick revision.

• Water naturally exists in three states.
• Evaporation occurs at all temperatures.
• Condensation is the opposite of evaporation.
• No new substance is formed during change of state.
• Wind increases the rate of evaporation.
• Humidity decreases evaporation.
• Evaporation produces cooling.
• Clouds are formed due to condensation.
• The Sun is the main source of energy for the water cycle.
• The water cycle maintains the balance of water in nature.

Quick Revision

Revise these points before your examination.

• Ice, water and water vapour are three states of the same substance.
• Melting changes solid into liquid.
• Freezing changes liquid into solid.
• Evaporation changes liquid into gas.
• Condensation changes gas into liquid.
• Higher temperature increases evaporation.
• Greater surface area increases evaporation.
• Moving air increases evaporation.
• High humidity slows evaporation.
• Sweating cools the body due to evaporation.
• Clouds form because of condensation.
• Rain is an important stage of the water cycle.
• The water cycle is essential for life on Earth.

A Journey through States of Water

Chapter 8. A Journey through States of Water

Water is one of the most important natural resources on Earth. It exists in three states—solid, liquid, and gas. Heat and cooling change water from one state to another, making many natural processes possible.

Detailed Notes

States of Water

States of Water: Water exists in three physical states—solid, liquid, and gas.

Three States of Water

(i) Solid – Ice

(ii) Liquid – Water

(iii) Gas – Water Vapour

Characteristics of Water

(i) Water changes its state on heating or cooling.

(ii) All three states are forms of the same substance.

(iii) These changes are physical changes.

Properties of Solid, Liquid and Gas

Properties of Matter: Solid, liquid, and gas differ in shape, volume, and movement of particles.

Property	Solid	Liquid	Gas
Shape	Fixed	Takes the shape of the container	No fixed shape
Volume	Fixed	Fixed	No fixed volume
Can Flow	No	Yes	Yes
Compressibility	Very Low	Very Low	High

Melting

Melting: Melting is the process in which a solid changes into a liquid on heating.

Examples of Melting

(i) Ice changes into water.

(ii) Ice cream melts in summer.

(iii) Butter melts on heating.

Key Points

(i) Heat is absorbed during melting.

(ii) Only the state changes.

(iii) No new substance is formed.

Freezing

Freezing: Freezing is the process in which a liquid changes into a solid on cooling.

Examples of Freezing

(i) Water changes into ice.

(ii) Ice cubes are made in a freezer.

(iii) Lakes freeze in very cold regions.

Key Points

(i) Heat is removed during freezing.

(ii) Liquid water becomes solid ice.

(iii) It is the opposite of melting.

Evaporation

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

Examples of Evaporation

(i) Drying of wet clothes.

(ii) Drying of wet roads.

(iii) Evaporation of sweat.

(iv) Drying of a mopped floor.

Characteristics of Evaporation

(i) Occurs at any temperature.

(ii) Takes place from the surface of water.

(iii) Absorbs heat from the surroundings.

Factors Affecting Evaporation

Factors Affecting Evaporation: The rate of evaporation depends on temperature, wind, surface area, and humidity.

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

Cooling Effect of Evaporation

Cooling Effect of Evaporation: Evaporation absorbs heat from the surroundings and produces a cooling effect.

Examples

(i) Sweating cools our body.

(ii) Water in an earthen pot remains cool.

(iii) Hand sanitiser feels cool after use.

(iv) Sprinkling water cools the floor.

Condensation

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

Examples of Condensation

(i) Water droplets on a cold bottle.

(ii) Dew on grass.

(iii) Fog on a bathroom mirror.

(iv) Water droplets on a vessel lid.

Key Points

(i) Water vapour loses heat.

(ii) Liquid water is formed.

(iii) It is the opposite of evaporation.

Cloud Formation

Cloud Formation: Clouds are formed when water vapour cools and condenses into tiny water droplets.

Steps of Cloud Formation

(i) Water evaporates due to the Sun's heat.

(ii) Water vapour rises into the atmosphere.

(iii) Vapour cools and condenses.

(iv) Tiny droplets join together to form clouds.

Key Points

(i) Clouds are made of tiny water droplets.

(ii) Heavy clouds produce rain.

The Water Cycle

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

Stages of the Water Cycle

(i) Evaporation

(ii) Condensation

(iii) Precipitation

(iv) Collection

Stage	Description
Evaporation	Water changes into water vapour.
Condensation	Water vapour forms clouds.
Precipitation	Water falls as rain, snow, or hail.
Collection	Water collects in rivers, lakes, and oceans.

Importance of the Water Cycle

(i) Recycles water in nature.

(ii) Maintains the water balance.

(iii) Provides fresh water for living organisms.

Importance of Water

Importance of Water: Water is essential for the survival of all living organisms.

Uses of Water

(i) Drinking

(ii) Cooking

(iii) Washing and cleaning

(iv) Farming and irrigation

(v) Industries

(vi) Producing electricity

Applications in Daily Life

Applications: The changes in the states of water can be seen in our daily life.

Examples

(i) Drying of clothes.

(ii) Cooling by sweating.

(iii) Making ice cubes.

(iv) Formation of clouds and rain.

(v) Cool water in an earthen pot.

Water Conservation

Water Conservation: Water conservation means using water wisely and avoiding its wastage.

Ways to Save Water

(i) Turn off taps after use.

(ii) Repair leaking taps.

(iii) Collect rainwater.

(iv) Use water carefully.

(v) Do not pollute water sources.

Quick Revision

(i) Water exists in three states—solid, liquid, and gas.

(ii) Melting changes solid into liquid.

(iii) Freezing changes liquid into solid.

(iv) Evaporation changes liquid into water vapour.

(v) Condensation changes water vapour into liquid.

(vi) Evaporation causes cooling.

(vii) Clouds are formed by condensation.

(viii) The water cycle continuously recycles water.

(ix) Water is essential for all living organisms.

(x) We should save and use water wisely.

Keywords

Melting: Change of solid into liquid.

Freezing: Change of liquid into solid.

Evaporation: Change of liquid into water vapour.

Condensation: Change of water vapour into liquid.

Water Cycle: Continuous movement of water in nature.

Water Conservation: Careful and wise use of water.

A Journey through States of Water

Chapter 8. A Journey through States of Water

This assignment is prepared according to the latest CBSE competency-based pattern and the NCERT Curiosity textbook. It includes objective, subjective, competency-based, case study, and HOTS questions to help students revise the complete chapter effectively.

Assignments – What Have You Learned?

Attempt all the following questions without referring to the textbook. These questions will strengthen your understanding of the chapter and improve your problem-solving skills.

Part A: Fill in the Blanks

Complete the following statements with suitable words.

1. Water naturally exists in __________ different physical states.
2. The gaseous form of water is called __________.
3. The process of changing liquid water into water vapour is called __________.
4. Water vapour changes into liquid water by the process of __________.
5. The conversion of ice into water is called __________.
6. The conversion of water into ice is called __________.
7. Evaporation produces a __________ effect.
8. High __________ increases the rate of evaporation.
9. The continuous circulation of water in nature is called the __________.
10. Clouds are formed due to the process of __________.

Part B: True or False

Write True or False for each statement.

1. Ice has a fixed shape and fixed volume.
2. Water vapour has a fixed shape.
3. Evaporation takes place only at 100°C.
4. Humidity decreases the rate of evaporation.
5. Condensation is the opposite of evaporation.
6. Clouds are formed due to melting.
7. Sweating cools our body because of evaporation.
8. Water cycle helps recycle water in nature.
9. Water is a renewable natural resource.
10. No new substance is formed during the change of state of water.

Part C: Match the Following

Match Column A with the correct option in Column B.

Column A	Column B
1. Evaporation	(a) Water changes into ice
2. Condensation	(b) Cooling effect
3. Freezing	(c) Water vapour changes into liquid
4. Melting	(d) Ice changes into water
5. Sweating	(e) Water changes into vapour

Part D: One Word Answer

Answer each question in one word or one term.

1. What is the gaseous form of water?
2. Which process changes water into vapour?
3. Which process forms clouds?
4. Name the cycle that continuously recycles water.
5. Which factor present in air slows down evaporation?

Part E: Very Short Answer Questions

Answer the following questions in one or two sentences.

1. What are the three states of water?
2. Why does evaporation produce cooling?
3. Define condensation.
4. What is humidity?
5. Why do wet clothes dry faster in sunlight?

Part F: Short Answer Questions

Answer the following questions in about 30–50 words.

1. Differentiate between evaporation and condensation.
2. Explain any four factors affecting evaporation.
3. Describe the formation of dew.
4. Why does water remain cool in an earthen pot?
5. Explain the importance of the water cycle.

Part G: Long Answer Questions

Answer the following questions in detail.

1. Describe the three states of water with suitable examples.
2. Explain the changes of state of water with the help of a flow diagram.
3. Describe the complete water cycle with labelled stages.
4. Explain the cooling effect of evaporation with suitable daily-life examples.
5. Discuss the importance of water conservation and suggest practical methods to save water.

Part H: Case Study

Read the passage carefully and answer the questions that follow.

Rohan washed his school uniform in the morning and hung it outside in the sunlight. A gentle breeze was blowing throughout the day. By afternoon, the clothes had become completely dry. Later, he noticed tiny water droplets on the outside of a bottle taken out from the refrigerator.

1. Which process helped the clothes dry?
2. Why did the clothes dry faster in the sunlight?
3. How did the wind help in drying the clothes?
4. Why did water droplets appear on the outside of the cold bottle?
5. Name the two changes of state involved in this case.

Part I: Competency-Based Questions

Answer the following questions by applying your understanding of the chapter.

1. Why does a wet towel dry faster when spread open than when folded?
2. Why do farmers prefer open fields with moving air for drying harvested grains?
3. Explain why artificial grass feels warmer than natural grass on a hot day.
4. Why do people feel cooler after taking a bath during summer?
5. How does the water cycle help maintain the balance of nature?

Part J: HOTS (Higher Order Thinking Skills)

Think carefully and answer the following questions.

1. If there were no evaporation on Earth, what major changes would occur in our environment?
2. How would life be affected if condensation never occurred?
3. Why is evaporation slower on humid days even when the temperature is high?
4. Suppose all the glaciers on Earth melted rapidly. What effects might this have on humans and other living organisms?
5. Why is understanding the water cycle important for protecting water resources?

Self-Assessment Checklist

Tick (✔) the statements after completing this chapter.

• ☐ I can identify the three states of water.
• ☐ I can explain melting, freezing, evaporation, and condensation.
• ☐ I know the factors affecting evaporation.
• ☐ I can explain the cooling effect of evaporation.
• ☐ I understand how clouds are formed.
• ☐ I can describe the stages of the water cycle.
• ☐ I can solve competency-based and case study questions.
• ☐ I am confident about this chapter for my CBSE examination.