Chapter 8: A Journey through States of Water

Introduction

Water exists in three states: solid (ice), liquid (water), and gas (water vapour). It continuously changes from one state to another through natural processes. Understanding these changes is essential in science and daily life.

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1. States of Water

1. Solid – Ice: fixed shape, fixed volume, particles closely packed
2. Liquid – Water: takes shape of container, fixed volume, particles less tightly packed
3. Gas – Water vapour/Steam: no fixed shape, no fixed volume, particles widely separated

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2. Changes of State

Process	From → To	Example
Melting	Solid → Liquid	Ice to water
Freezing	Liquid → Solid	Water to ice
Evaporation	Liquid → Gas	Water to vapour in sun
Condensation	Gas → Liquid	Dew formation
Sublimation	Solid → Gas	Camphor, naphthalene
Deposition	Gas → Solid	Frost formation

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3. Water Cycle in Nature

• Water continuously moves through evaporation, condensation, precipitation, and collection.
• Sun provides energy for evaporation.
• Rain replenishes rivers, lakes, and underground water.

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4. Key Points to Remember

• Water exists in three states: solid, liquid, gas.
• Heat energy causes changes in state.
• The water cycle maintains the balance of water on Earth.
• Evaporation and condensation are essential for rainfall.

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Questions – A Journey through States of Water

1. Very Short Answer (1 mark)

1. Name the three states of water.
2. What is melting?
3. What is condensation?
4. Give an example of sublimation.
5. What is deposition?
6. Name the process in which water becomes vapour.
7. Give an example of freezing.
8. Which state of water has no fixed shape or volume?
9. Why is evaporation important in nature?
10. What is formed when water vapour cools down?

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2. Multiple Choice Questions (MCQ)

1. Ice turning into water is called:
   a) Freezing
   b) Melting
   c) Condensation
   d) Sublimation
2. Dew on grass is an example of:
   a) Evaporation
   b) Condensation
   c) Melting
   d) Freezing
3. Water vapour changes into liquid water during:
   a) Evaporation
   b) Condensation
   c) Melting
   d) Sublimation
4. Camphor turning directly into gas is:
   a) Melting
   b) Sublimation
   c) Freezing
   d) Condensation
5. Rain is part of which natural cycle?
   a) Carbon cycle
   b) Water cycle
   c) Nitrogen cycle
   d) Rock cycle

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3. Fill in the Blanks

1. Water in the form of ice is in __________ state.
2. The process of liquid turning into gas is called __________.
3. Frost formation is an example of __________.
4. The Sun provides energy for __________.
5. Condensation results in the formation of __________.

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4. True/False Type

1. Water vapour has a fixed shape and volume. (True/False)
2. Melting occurs when heat is absorbed. (True/False)
3. Evaporation is part of the water cycle. (True/False)
4. Freezing changes liquid water into ice. (True/False)
5. Deposition is gas turning directly into solid. (True/False)

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5. Short Answer Questions (2–3 marks)

1. Define melting and give an example.
2. What is sublimation?
3. Name two processes where heat is absorbed.
4. What is the water cycle?
5. Why is condensation important for rainfall?

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6. Long Answer Questions (4–5 marks)

1. Describe the three states of water with their properties.
2. Explain the processes of melting, freezing, evaporation, and condensation.
3. What is sublimation? Give examples.
4. Explain the water cycle and its significance.
5. How does heat energy affect the changes in the state of water?

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7. Higher-Order Thinking (HOT) & Application

1. Why does ice melt faster in sunlight than in shade?
2. How can condensation be demonstrated at home?
3. Explain how water cycles help maintain life on Earth.

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8. Passage-Based Questions

Read the passage and answer:
Water exists in three states: solid, liquid, and gas. Heat energy causes water to change its state. Evaporation and condensation are essential processes in the water cycle, which ensures the availability of water on Earth.

1. Name the three states of water.
2. What causes changes in the state of water?
3. Which two processes are essential in the water cycle?
4. Why is the water cycle important?

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Answer Key – A Journey through States of Water

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1. Very Short Answer

1. Solid, Liquid, Gas
2. Solid turning into liquid
3. Gas turning into liquid
4. Camphor, naphthalene
5. Gas turning directly into solid
6. Evaporation
7. Water to ice
8. Gas
9. It helps form clouds and rain
10. Liquid water or dew

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2. MCQ Answers

1. b) Melting
2. b) Condensation
3. b) Condensation
4. b) Sublimation
5. b) Water cycle

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3. Fill in the Blanks

1. solid
2. evaporation
3. deposition
4. Sun
5. dew or rain

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4. True/False

1. False
2. True
3. True
4. True
5. True

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5. Short Answer

1. Melting: Solid → Liquid; e.g., Ice → Water
2. Sublimation: Solid → Gas without becoming liquid; e.g., Camphor
3. Melting and Evaporation
4. Continuous movement of water through evaporation, condensation, precipitation, and collection
5. Condensation forms clouds and rain, replenishing water resources

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6. Long Answer

1. Solid – fixed shape and volume; Liquid – fixed volume, takes shape of container; Gas – no fixed shape or volume
2. Melting – solid → liquid; Freezing – liquid → solid; Evaporation – liquid → gas; Condensation – gas → liquid
3. Sublimation – direct solid → gas; examples: Camphor, naphthalene
4. Water cycle: Evaporation → Condensation → Precipitation → Collection; significance – maintains water balance
5. Heat energy causes particles to move faster, leading to melting or evaporation; cooling causes condensation or freezing

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7. HOT & Application

1. Sunlight provides more heat energy, increasing particle movement, so ice melts faster
2. Place a cold metal plate over steam – water droplets form due to condensation
3. Water cycle ensures water availability, supports plants, animals, and humans, and maintains climate balance

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8. Passage-Based

1. Solid, Liquid, Gas
2. Heat energy
3. Evaporation and Condensation
4. Maintains water availability for life and ecosystems