NCERT Class 5 The World Around Us / EVS • Classic CBSE Track

Chapter 7: Experiments with Water

Floating & Sinking, Buoyancy & Density, Dead Sea Salinity & Mahatma Gandhi's Dandi March | CBSE Session 2026–27

Core Pedagogical Competencies & Concepts
  • Whether an object floats or sinks in water depends on its density and buoyant force (upward thrust of water).
  • An iron nail sinks because it is small and dense, while an enormous steel ship floats because its hollow shape displaces a weight of water equal to its own weight.
  • The Dead Sea is the saltiest water body on Earth (~300 grams of salt per litre). Its density is so high that a human body naturally floats on its surface without drowning.
  • Solubility: Substances like salt and sugar dissolve completely in water; chalk, oil, and sand do not dissolve.
  • Mahatma Gandhi led the historic Dandi March in 1930 from Ahmedabad to Dandi seashore to protest against the British tax on natural salt.
Floating vs Sinking & The Dead Sea Phenomenon Iron Nail Sinks Katori Floats Saline Water (Egg Floats) 🚶‍♂️ Dandi March 1930 Salt is natural gift

All Textbook Exercises & In-Text Tasks (22 Questions)

100% Complete Ingestion
Q1 Textbook Exercise
Why does a small iron nail sink in water, while a giant ship made of iron and steel floats easily on the sea?
[3 Marks]
✅ Step-by-Step Solution & Working
An iron nail is solid and dense; the weight of water it displaces is smaller than its own weight, causing it to sink. In contrast, an enormous iron ship is designed with a wide, hollow hull filled with air. The total volume of the ship displaces an amount of water whose buoyant force is greater than the total weight of the ship, allowing it to float safely.
CBSE Step-by-Step Marking Scheme
Solid nail displaces less water than its weight 1.5 Marks
Hollow ship hull displaces massive volume equal to ship weight 1.5 Marks
Q2 Textbook Exercise
What is the Dead Sea? Why is it impossible for a swimmer to drown in the Dead Sea?
[3 Marks]
✅ Step-by-Step Solution & Working
The Dead Sea is a salt lake bordered by Jordan and Israel. It is the saltiest body of water on Earth, containing approximately 300 grams of dissolved salt per litre of water. Because of this extreme salt concentration, the density of the water is much higher than the density of the human body. As a result, an upward buoyant force naturally pushes a swimmer up, allowing a person to float effortlessly on the surface like a raft.
CBSE Step-by-Step Marking Scheme
Salinity level (300 grams of salt per litre) 1.5 Marks
Water density higher than human body providing automatic buoyancy 1.5 Marks
Q3 Textbook Exercise
Why did Mahatma Gandhi organize the Dandi March in 1930? What was the outcome of this protest?
[4 Marks]
✅ Step-by-Step Solution & Working
In 1930, the British colonial government passed the Salt Act, prohibiting Indians from manufacturing salt from seawater and placing a heavy tax on salt. Since salt is an essential daily food requirement for everyone, rich and poor alike, Mahatma Gandhi organized the Dandi March:
  • Gandhi and his followers walked over 385 kilometres on foot from Sabarmati Ashram in Ahmedabad to the coastal village of Dandi.
  • On 6 April 1930, Gandhi picked up a handful of natural salt from the seashore, boldly defying the British law.
  • The march triggered the nationwide Civil Disobedience Movement, demonstrating that natural resources given by nature should never be taxed.
CBSE Step-by-Step Marking Scheme
Background of the unjust British Salt Act and tax 1.5 Marks
March from Sabarmati to Dandi (385 km) 1.5 Marks
Breaking of law and initiation of Civil Disobedience 1 Mark
Q4 Textbook Exercise
State whether the following float or sink in water, and give the scientific reason for each: (a) An empty plastic bottle, (b) A plastic bottle tightly filled with sand, (c) An iron pin, (d) An aluminium foil balled tightly vs spread wide.
[4 Marks]
✅ Step-by-Step Solution & Working
  • (a) Empty plastic bottle: Floats, because it contains air and its average density is much lower than water.
  • (b) Plastic bottle filled with sand: Sinks, because dense sand increases its total weight beyond the buoyant water displacement.
  • (c) An iron pin: Sinks, because solid iron has higher density than water and displaces negligible water volume.
  • (d) Aluminium foil:
    • Spread wide into a flat cup: Floats, because its bowl shape displaces more water.
    • Pressed into a tight, dense ball: Sinks, because high compactness decreases displacement volume.
CBSE Step-by-Step Marking Scheme
Correct floating/sinking prediction for (a) and (b) 2 Marks
Correct prediction and density/shape explanation for (c) and (d) 2 Marks
Q5 Textbook Exercise
How can salt be extracted from seawater in coastal areas? Describe the process of salt pans.
[3 Marks]
✅ Step-by-Step Solution & Working
Salt is manufactured through solar evaporation in shallow coastal beds:
  1. Seawater is channelled into large, shallow rectangular plots called salt pans (Namak ke Khet) bordered by mud bunds.
  2. The water is left exposed to the blazing sun and strong sea winds.
  3. Water slowly evaporates into the atmosphere as water vapour, leaving behind solid mounds of crystalline white raw salt.
  4. The harvested salt crystals are collected, washed, iodised, and packaged.
CBSE Step-by-Step Marking Scheme
Channelling into shallow salt pans 1.5 Marks
Solar evaporation leaving solid salt crystals 1.5 Marks
Q6 Think and Discuss • Environmental Science & Ecology • Experiments with Water
[Textbook Activity & Question 1] In 'Experiments with Water', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In Experiments with Water, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q7 Find Out and Write • Observational Field Study • Experiments with Water
[Textbook Activity & Question 2] In 'Experiments with Water', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In Experiments with Water, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q8 Scientific Investigation • Ecosystem Relationships • Experiments with Water
[Textbook Activity & Question 3] In 'Experiments with Water', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In Experiments with Water, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q9 Traditional Wisdom & Community Stewardship • Conservation • Experiments with Water
[Textbook Activity & Question 4] In 'Experiments with Water', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In Experiments with Water, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q10 Survey & Data Collection • Experiential Inquiry • Experiments with Water
[Textbook Activity & Question 5] In 'Experiments with Water', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In Experiments with Water, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q11 Health, Diet & Human Biology • Nutritional Science • Experiments with Water
[Textbook Activity & Question 6] In 'Experiments with Water', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In Experiments with Water, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q12 Disaster Preparedness & Climate Resilience • Geography • Experiments with Water
[Textbook Activity & Question 7] In 'Experiments with Water', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In Experiments with Water, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q13 Biodiversity & Habitat Adaptations • Wildlife Protection • Experiments with Water
[Textbook Activity & Question 8] In 'Experiments with Water', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In Experiments with Water, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q14 Think and Discuss • Environmental Science & Ecology • Experiments with Water
[Textbook Activity & Question 9] In 'Experiments with Water', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In Experiments with Water, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q15 Find Out and Write • Observational Field Study • Experiments with Water
[Textbook Activity & Question 10] In 'Experiments with Water', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In Experiments with Water, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q16 Scientific Investigation • Ecosystem Relationships • Experiments with Water
[Textbook Activity & Question 11] In 'Experiments with Water', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In Experiments with Water, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q17 Traditional Wisdom & Community Stewardship • Conservation • Experiments with Water
[Textbook Activity & Question 12] In 'Experiments with Water', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In Experiments with Water, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q18 Survey & Data Collection • Experiential Inquiry • Experiments with Water
[Textbook Activity & Question 13] In 'Experiments with Water', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In Experiments with Water, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q19 Health, Diet & Human Biology • Nutritional Science • Experiments with Water
[Textbook Activity & Question 14] In 'Experiments with Water', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In Experiments with Water, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q20 Disaster Preparedness & Climate Resilience • Geography • Experiments with Water
[Textbook Activity & Question 15] In 'Experiments with Water', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In Experiments with Water, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q21 Biodiversity & Habitat Adaptations • Wildlife Protection • Experiments with Water
[Textbook Activity & Question 16] In 'Experiments with Water', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In Experiments with Water, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q22 Think and Discuss • Environmental Science & Ecology • Experiments with Water
[Textbook Activity & Question 17] In 'Experiments with Water', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In Experiments with Water, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
🌟 NEP 2020 Competency-Based Case Study

Factors Affecting the Rate of Dissolution

While preparing lemonade for guests on a hot summer afternoon, Rohit added ice cubes before adding sugar and noticed the sugar took a very long time to dissolve.

Analytical Task: Explain three scientific methods by which sugar can be made to dissolve much faster in water.
Evaluation & Model Answer:
Three Methods to Accelerate Dissolution: 1. Stirring: Stirring moves water molecules rapidly across sugar crystals, exposing fresh solvent molecules to solute surfaces. 2. Using Warm Water: Warm water molecules possess higher kinetic energy, separating sugar molecules much faster than cold water. (Add ice only AFTER sugar dissolves). 3. Using Powdered Sugar: Fine powder has a vastly greater surface area than large crystal cubes, speeding up dissolution.
Rubric: 1 Mark for Stirring + 2 Marks for Warm water kinetic energy + 2 Marks for Powdered surface area = 5 Marks