Are you a Class 9 ICSE student preparing for your Chemistry exams? Water is one of the most important chapters in the ICSE Class 9 Chemistry syllabus. At Dhingra Classes, Nashik, we have designed this comprehensive guide to help you master every concept with 50 solved MCQs, 15 solved short answer questions, and 15 solved long answer questions.

This article covers water cycle, types of water, hard and soft water, removal of hardness, water pollution, and water treatment — all explained step-by-step for easy understanding.

📚 Introduction to Water

Water (H₂O) is the most abundant compound on Earth’s surface, covering about 71% of the planet. It is essential for all forms of life and is called the “universal solvent.”

🔑 Key Facts:

• Molecular Formula: H₂O

• Molecular Mass: 18 g/mol

• Nature: Neutral (pH = 7)

• Solubility: Universal solvent

• States: Solid (ice), Liquid (water), Gas (steam)

• Boiling Point: 100°C

• Freezing Point: 0°C

💧 Water Cycle

The water cycle (hydrological cycle) is the continuous movement of water between the Earth’s surface and the atmosphere through:

1. Evaporation: Water changes to vapour

2. Transpiration: Plants release water vapour

3. Condensation: Vapour changes to droplets

4. Precipitation: Rain, snow, hail

5. Collection: Water bodies

💧 Types of Water

💧 Hard and Soft Water

Hard Water:

• Contains dissolved salts of calcium and magnesium

• Does not lather easily with soap

• Forms scum with soap

Soft Water:

• Free from calcium and magnesium salts

• Lathers easily with soap

• No scum formation

Types of Hardness:

1. Temporary Hardness: Due to bicarbonates of Ca and Mg

2. Permanent Hardness: Due to sulphates and chlorides of Ca and Mg

Removal of Hardness:

1. Boiling: Removes temporary hardness

2. Clark’s Method: Removes temporary hardness

3. Ion Exchange: Removes both types

4. Synthetic Resin: Removes both types

5. Distillation: Removes all hardness

💧 Water Pollution

Water pollution is the contamination of water bodies by harmful substances.

Sources:

1. Industrial waste

2. Sewage

3. Agricultural runoff

4. Oil spills

5. Plastic waste

Effects:

1. Waterborne diseases

2. Death of aquatic life

3. Ecosystem imbalance

Treatment:

1. Sedimentation

2. Filtration

3. Chlorination

4. UV treatment

📝 SECTION 1: 50 SOLVED MCQs on Water

Q1. The molecular formula of water is:

(a) H₂O (b) H₂O₂ (c) HO (d) H₃O
Ans: (a) H₂O

Q2. The molecular mass of water is:

(a) 16 (b) 17 (c) 18 (d) 19
Ans: (c) 18

Q3. The purest form of water is:

(a) Rainwater (b) Distilled water (c) Mineral water (d) Sea water
Ans: (b) Distilled water

Q4. The water cycle involves:

(a) Evaporation (b) Condensation (c) Precipitation (d) All of these
Ans: (d) All of these

Q5. Hard water contains:

(a) Sodium salts (b) Calcium and magnesium salts (c) Potassium salts (d) Iron salts
Ans: (b) Calcium and magnesium salts

Q6. Temporary hardness is due to:

(a) Sulphates (b) Chlorides (c) Bicarbonates (d) Nitrates
Ans: (c) Bicarbonates

Q7. Permanent hardness is due to:

(a) Bicarbonates (b) Sulphates and chlorides (c) Carbonates (d) Nitrates
Ans: (b) Sulphates and chlorides

Q8. Temporary hardness can be removed by:

(a) Boiling (b) Filtration (c) Chlorination (d) Distillation
Ans: (a) Boiling

Q9. Permanent hardness can be removed by:

(a) Boiling (b) Ion exchange (c) Sedimentation (d) Filtration
Ans: (b) Ion exchange

Q10. The method used to remove both types of hardness is:

(a) Boiling (b) Clark’s method (c) Ion exchange (d) Sedimentation
Ans: (c) Ion exchange

Q11. Sea water contains about:

(a) 1.5% salts (b) 2.5% salts (c) 3.5% salts (d) 4.5% salts
Ans: (c) 3.5% salts

Q12. The pH of pure water is:

(a) 5 (b) 6 (c) 7 (d) 8
Ans: (c) 7

Q13. Water is called the universal solvent because:

(a) It is abundant (b) It dissolves many substances (c) It is liquid (d) It is pure
Ans: (b) It dissolves many substances

Q14. The boiling point of water is:

(a) 0°C (b) 50°C (c) 100°C (d) 150°C
Ans: (c) 100°C

Q15. The freezing point of water is:

(a) 0°C (b) 10°C (c) -10°C (d) 100°C
Ans: (a) 0°C

Q16. Which gas dissolves in water to form carbonic acid?

(a) Oxygen (b) Nitrogen (c) Carbon dioxide (d) Hydrogen
Ans: (c) Carbon dioxide

Q17. The process of removing salts from sea water is:

(a) Filtration (b) Distillation (c) Sedimentation (d) Chlorination
Ans: (b) Distillation

Q18. Hard water does not lather with soap because:

(a) It is acidic (b) It contains Ca and Mg ions (c) It is basic (d) It is pure
Ans: (b) It contains Ca and Mg ions

Q19. The scum formed with hard water and soap is:

(a) Calcium stearate (b) Sodium stearate (c) Magnesium sulphate (d) Calcium carbonate
Ans: (a) Calcium stearate

Q20. Clark’s method is used to remove:

(a) Permanent hardness (b) Temporary hardness (c) Both (d) None
Ans: (b) Temporary hardness

Q21. The chemical used in Clark’s method is:

(a) Sodium carbonate (b) Calcium hydroxide (c) Sodium chloride (d) Calcium carbonate
Ans: (b) Calcium hydroxide

Q22. Ion exchange resins contain:

(a) Sodium ions (b) Calcium ions (c) Magnesium ions (d) Potassium ions
Ans: (a) Sodium ions

Q23. Water pollution is caused by:

(a) Industrial waste (b) Sewage (c) Agricultural runoff (d) All of these
Ans: (d) All of these

Q24. Waterborne diseases include:

(a) Cholera (b) Typhoid (c) Jaundice (d) All of these
Ans: (d) All of these

Q25. The process of adding chlorine to water is:

(a) Sedimentation (b) Filtration (c) Chlorination (d) Distillation
Ans: (c) Chlorination

Q26. The process of settling down of particles is:

(a) Sedimentation (b) Filtration (c) Chlorination (d) Distillation
Ans: (a) Sedimentation

Q27. The process of passing water through layers of sand is:

(a) Sedimentation (b) Filtration (c) Chlorination (d) Distillation
Ans: (b) Filtration

Q28. The method used to kill germs in water is:

(a) Sedimentation (b) Filtration (c) Chlorination (d) Distillation
Ans: (c) Chlorination

Q29. The purest form of natural water is:

(a) Sea water (b) River water (c) Rainwater (d) Well water
Ans: (c) Rainwater

Q30. The density of water is maximum at:

(a) 0°C (b) 4°C (c) 10°C (d) 100°C
Ans: (b) 4°C

Q31. The specific heat capacity of water is:

(a) 1 J/g°C (b) 2 J/g°C (c) 4.2 J/g°C (d) 10 J/g°C
Ans: (c) 4.2 J/g°C

Q32. Water is a:

(a) Polar molecule (b) Non-polar molecule (c) Ionic compound (d) Metallic compound
Ans: (a) Polar molecule

Q33. The bond angle in water is:

(a) 90° (b) 104.5° (c) 109.5° (d) 120°
Ans: (b) 104.5°

Q34. The process of water changing to vapour is:

(a) Condensation (b) Evaporation (c) Precipitation (d) Sublimation
Ans: (b) Evaporation

Q35. The process of vapour changing to water is:

(a) Condensation (b) Evaporation (c) Precipitation (d) Sublimation
Ans: (a) Condensation

Q36. The process of water falling as rain is:

(a) Condensation (b) Evaporation (c) Precipitation (d) Sublimation
Ans: (c) Precipitation

Q37. The water cycle is also called:

(a) Carbon cycle (b) Hydrological cycle (c) Nitrogen cycle (d) Oxygen cycle
Ans: (b) Hydrological cycle

Q38. The main source of water on Earth is:

(a) Rivers (b) Lakes (c) Oceans (d) Wells
Ans: (c) Oceans

Q39. The percentage of fresh water on Earth is about:

(a) 1% (b) 3% (c) 10% (d) 25%
Ans: (b) 3%

Q40. The process of removing dissolved salts from water is:

(a) Filtration (b) Desalination (c) Sedimentation (d) Chlorination
Ans: (b) Desalination

Q41. The chemical formula of heavy water is:

(a) H₂O (b) D₂O (c) H₂O₂ (d) T₂O
Ans: (b) D₂O

Q42. Heavy water is used in:

(a) Nuclear reactors (b) Drinking (c) Irrigation (d) Cooking
Ans: (a) Nuclear reactors

Q43. The hardness of water is measured in:

(a) ppm (b) mg/L (c) Both (d) None
Ans: (c) Both

Q44. The temporary hardness of water can also be removed by:

(a) Adding washing soda (b) Adding baking soda (c) Adding lime (d) All of these
Ans: (d) All of these

Q45. The permanent hardness of water can be removed by:

(a) Boiling (b) Adding washing soda (c) Adding lime (d) Filtration
Ans: (b) Adding washing soda

Q46. The chemical formula of washing soda is:

(a) Na₂CO₃ (b) NaHCO₃ (c) NaOH (d) NaCl
Ans: (a) Na₂CO₃

Q47. The chemical formula of baking soda is:

(a) Na₂CO₃ (b) NaHCO₃ (c) NaOH (d) NaCl
Ans: (b) NaHCO₃

Q48. The chemical formula of lime is:

(a) CaO (b) Ca(OH)₂ (c) CaCO₃ (d) CaSO₄
Ans: (b) Ca(OH)₂

Q49. The chemical formula of gypsum is:

(a) CaSO₄ (b) CaSO₄·2H₂O (c) CaCO₃ (d) CaO
Ans: (b) CaSO₄·2H₂O

Q50. The chemical formula of plaster of Paris is:

(a) CaSO₄ (b) CaSO₄·½H₂O (c) CaSO₄·2H₂O (d) CaCO₃
Ans: (b) CaSO₄·½H₂O

📝 SECTION 2: 15 SOLVED SHORT ANSWER QUESTIONS on Water

Q1. What is the water cycle?

Ans:
The water cycle is the continuous movement of water between the Earth’s surface and the atmosphere through evaporation, condensation, precipitation, and collection.

Q2. What is hard water?

Ans:
Hard water is water that contains dissolved salts of calcium and magnesium. It does not lather easily with soap.

Q3. What is soft water?

Ans:
Soft water is water that is free from calcium and magnesium salts. It lathers easily with soap.

Q4. What is temporary hardness?

Ans:
Temporary hardness is due to the presence of bicarbonates of calcium and magnesium. It can be removed by boiling.

Q5. What is permanent hardness?

Ans:
Permanent hardness is due to the presence of sulphates and chlorides of calcium and magnesium. It cannot be removed by boiling.

Q6. How is temporary hardness removed?

Ans:
Temporary hardness is removed by:

1. Boiling

2. Clark’s method (adding calcium hydroxide)

Q7. How is permanent hardness removed?

Ans:
Permanent hardness is removed by:

1. Ion exchange method

2. Adding washing soda

3. Distillation

Q8. What is the principle of ion exchange?

Ans:
Ion exchange resins exchange sodium ions with calcium and magnesium ions, softening the water.

Q9. What is water pollution?

Ans:
Water pollution is the contamination of water bodies by harmful substances like industrial waste, sewage, and agricultural runoff.

Q10. Name two waterborne diseases.

Ans:

1. Cholera

2. Typhoid

Q11. What is chlorination?

Ans:
Chlorination is the process of adding chlorine to water to kill germs and make it safe for drinking.

Q12. What is sedimentation?

Ans:
Sedimentation is the process of allowing suspended particles to settle down at the bottom of a container.

Q13. What is filtration?

Ans:
Filtration is the process of passing water through layers of sand and gravel to remove suspended impurities.

Q14. Why is water called the universal solvent?

Ans:
Water is called the universal solvent because it dissolves a wide variety of substances.

Q15. What is heavy water?

Ans:
Heavy water is deuterium oxide (D₂O). It is used in nuclear reactors as a moderator.

📝 SECTION 3: 15 SOLVED LONG ANSWER QUESTIONS on Water

Q1. Explain the water cycle with a diagram.

Ans:
The water cycle involves:

1. Evaporation: Water from oceans, rivers, and lakes changes to vapour.

2. Transpiration: Plants release water vapour.

3. Condensation: Vapour rises, cools, and forms clouds.

4. Precipitation: Rain, snow, or hail falls.

5. Collection: Water collects in rivers, lakes, and oceans.

Q2. Differentiate between hard water and soft water.

Ans:

Q3. Explain the types of hardness of water.

Ans:

1. Temporary Hardness: Due to bicarbonates of Ca and Mg. Removed by boiling.

2. Permanent Hardness: Due to sulphates and chlorides of Ca and Mg. Removed by ion exchange or washing soda.

Q4. Explain the removal of temporary hardness by Clark’s method.

Ans:
Clark’s method:

• Add calculated amount of calcium hydroxide (lime) to hard water.

• Calcium bicarbonate reacts with lime to form calcium carbonate precipitate.

• Ca(HCO₃)₂ + Ca(OH)₂ → 2CaCO₃↓ + 2H₂O

• Filter to remove precipitate. Water becomes soft.

Q5. Explain the removal of permanent hardness by ion exchange.

Ans:
Ion exchange:

• Pass hard water through a column of ion exchange resin.

• Resin contains sodium ions.

• Calcium and magnesium ions are exchanged with sodium ions.

• Water becomes soft.

• Resin can be regenerated by passing brine solution.

Q6. Explain the causes and effects of water pollution.

Ans:
Causes:

1. Industrial waste

2. Sewage

3. Agricultural runoff

4. Oil spills

5. Plastic waste

Effects:

1. Waterborne diseases

2. Death of aquatic life

3. Ecosystem imbalance

4. Scarcity of clean water

Q7. Explain the steps in water treatment.

Ans:

1. Sedimentation: Suspended particles settle down.

2. Filtration: Water passes through sand and gravel.

3. Chlorination: Chlorine kills germs.

4. UV Treatment: UV light kills microorganisms.

5. Storage: Treated water is stored for distribution.

Q8. Explain the properties of water.

Ans:

1. Physical: Colourless, odourless, tasteless

2. Boiling Point: 100°C

3. Freezing Point: 0°C

4. Density: Maximum at 4°C

5. Specific Heat: 4.2 J/g°C

6. Solubility: Universal solvent

7. Polarity: Polar molecule

Q9. Explain the importance of water in daily life.

Ans:

1. Drinking and cooking

2. Agriculture and irrigation

3. Industrial processes

4. Electricity generation

5. Transportation

6. Recreation

7. Habitat for aquatic life

Q10. Explain the difference between temporary and permanent hardness.

Ans:

Q11. Explain the process of distillation for water purification.

Ans:
Distillation:

1. Heat water to boiling.

2. Water changes to vapour.

3. Vapour is cooled in a condenser.

4. Pure water is collected.

• Removes all dissolved salts and impurities.

Q12. Explain the role of water in the human body.

Ans:

1. Digestion and absorption

2. Transportation of nutrients

3. Regulation of body temperature

4. Removal of waste products

5. Lubrication of joints

6. Maintenance of blood pressure

Q13. Explain the causes of water scarcity.

Ans:

1. Overpopulation

2. Pollution

3. Deforestation

4. Climate change

5. Poor irrigation practices

6. Industrialization

7. Urbanization

Q14. Explain the methods of water conservation.

Ans:

1. Rainwater harvesting

2. Drip irrigation

3. Recycling of water

4. Fixing leaks

5. Awareness programs

6. Watershed management

Q15. Explain the importance of water conservation.

Ans:

1. Ensures availability for future

2. Protects ecosystem

3. Reduces water scarcity

4. Saves energy

5. Reduces cost

6. Maintains biodiversity

🎯 Exam Tips for Class 9 ICSE Chemistry Students

💧 Understand the water cycle — it is frequently asked

📝 Memorise the differences between hard and soft water

🔬 Practise diagram-based questions for full marks

📊 Learn the methods of removing hardness

✅ Revise the causes and effects of water pollution

🔗 Connect concepts to real-life applications like water treatment and conservation

📞 Contact Dhingra Classes Today!

📍 Address: Plot No 3, XQ3G+H3M Deacon Homes, 301C, opp. Metro Zone, near Guru Govind Sing, Samarth Nagar, Dnyaneshwar Nagar, Pathardi Phata, Nashik, Maharashtra 422009

📱 Phone: 98230 62106

🌐 Website: https://www.dhingraclassesnashik.com/

📧 Email: dhingraclassesnsk@gmail.com