If you are looking for DAV Class 4 Science Chapter 10 Question Answer Water Pollution of My Living World science book, then you are at the right place. Here at NCERTBooksPDF, Class 4 Science Chapter 10 exercises are solved with accurate, child-friendly explanations, clean tables, and complete solutions to help DAV students score top marks in their exams.
Table of Contents
- DAV Class 4 Science Chapter 10 Water Pollution Solutions
- A. Fill in the Blanks
- B. Write True or False (With Explanations)
- C. Tick the Correct Option
- D. Answer the Following Questions in Brief
- E. Answer the Following Questions (Detailed Explanations)
- Value-Based Questions
- Something to Do
DAV Class 4 Science Chapter 10 Water Pollution Solutions
DAV Class 4 Science Chapter 10 Water Pollution focuses on water contaminants, sources of river pollution (factory effluents, domestic sewage, agricultural chemicals, oil spills), impact on aquatic ecosystems and soil fertility, and preventive measures. Below are the complete textbook solutions.
A. Fill in the blanks.
1. Rain water is the purest form of water.
2. Water containing impurities is called polluted water.
3. Chemical fertilisers and pesticides, used by farmers, can cause water pollution.
4. Drinking polluted water can cause diseases like diarrhea and jaundice.
5. Industrial and agricultural wastes increase the growth of micro-organisms in water.
Answer: (1) Rain water | (2) polluted | (3) pesticides | (4) polluted | (5) Industrial
B. Write True or False for the following statements.
| Statement | True / False | Scientific Reason |
|---|---|---|
| 1. River water is the purest form of water. | False | River water carries dissolved salts, eroded soil, and waste; rainwater before touching ground is the purest natural water. |
| 2. Polluted water may contain dust, germs and smoke. | True | Atmospheric pollution and waste wash dust, toxic chemicals, and microbes into surface water. |
| 3. Throwing domestic waste, in rivers, causes water pollution. | True | Household trash, plastic bags, and detergent water spoil freshwater rivers. |
| 4. Increased growth of micro-organisms in water increases the amount of oxygen for aquatic animals. | False | Micro-organisms consume dissolved oxygen rapidly, causing oxygen starvation and death of aquatic animals. |
| 5. Use of chemical fertilisers helps in preventing water pollution. | False | Excess chemical fertilizers wash into water bodies during rains and cause severe eutrophication and pollution. |
C. Tick (✓) the correct option.
1. A disease that may be caused by drinking polluted water is—
(a) malaria
(b) cough
(c) cholera
(d) dengue
Answer: (c) cholera
Explanation: Cholera is a dangerous bacterial water-borne disease caused by drinking sewage-polluted water.
2. Polluted water should not be used for irrigation because—
(a) it can harm aquatic animals
(b) it pollutes river water
(c) it reduces fertility of soil
(d) it increases the production of crops
Answer: (c) it reduces fertility of soil
Explanation: Toxic chemicals and excess salts in polluted water alter soil chemistry, killing soil micro-fauna and decreasing agricultural fertility.
3. Oil spills in the sea are harmful because they—
(a) decrease the level of water in sea
(b) infect the aquatic plants
(c) increase the growth of micro-organisms in water
(d) cut off the supply of oxygen for aquatic animals
Answer: (d) cut off the supply of oxygen for aquatic animals
Explanation: Oil forms a non-porous floating layer on the ocean surface, preventing oxygen exchange with the atmosphere and suffocating marine life.
4. Pollution of river water can be reduced if—
(a) chemical fertilisers are used for increasing production of crops
(b) farmers use sprinklers for irrigating their fields
(c) water is allowed to stagnate around the river banks
(d) people do not wash clothes or bathe their cattle in rivers
Answer: (d) people do not wash clothes or bathe their cattle in rivers
Explanation: Stopping washing of clothes with detergents and cattle-bathing directly preserves clean river water.
D. Answer the following questions in brief.
1. Name any two materials which can make rain water impure.
Answer: Harmful industrial gases (like sulfur dioxide and nitrogen oxides) and dust/soot particles in the atmosphere.
2. Name any two human activities which can cause water pollution.
Answer:
(i) Washing clothes, utensils, and bathing cattle in rivers.
(ii) Dumping untreated domestic sewage and solid plastic wastes into water bodies.
3. Which two pollutants are often dumped by the factories into the rivers?
Answer: Toxic chemical effluents and heavy metal industrial waste materials.
4. Name any two diseases that may be caused by drinking polluted water.
Answer: Typhoid and Diarrhea (or Cholera / Jaundice).
5. Write the names of two types of materials, used by farmers, to increase the production of crops.
Answer: Chemical fertilisers and Pesticides.
E. Answer the following questions.
1. How do wastes, from factories and fields, affect aquatic animals?
Answer: Factory effluents contain poisonous heavy metals and chemicals that directly poison aquatic animals. Agricultural runoff containing chemical fertilizers stimulates excessive algal growth; when these algae decay, bacteria consume dissolved oxygen, causing severe oxygen depletion and mass death of fish and other aquatic organisms.
2. How can polluted water affect the crops?
Answer: When polluted water loaded with industrial chemicals or sewage salts is used for irrigating agricultural fields, it damages soil porosity, increases soil salinity, destroys beneficial earthworms and microbes, and stunts crop growth, leading to toxic crops and reduced crop yields.
3. Why are oil spills harmful for marine life?
Answer: Crude oil spilled from tankers floats on the sea surface, forming a dense, suffocating oil slick. This oil layer blocks atmospheric oxygen from dissolving into seawater, suffocates fish and crabs, coats seabird feathers so they cannot fly or stay warm, and damages delicate coastal coral reefs.
4. State any four effects of water pollution.
Answer: Four major effects of water pollution are:
- Poisonous chemical discharges kill thousands of fish, marine organisms, and aquatic plants.
- Consuming contaminated drinking water triggers fatal epidemics like cholera, diarrhea, typhoid, and hepatitis (jaundice).
- Irrigating agricultural farmland with polluted water decreases soil fertility and damages crop yield.
- Rivers and lakes lose their recreational and aesthetic beauty, turning into foul-smelling open drains.
5. State four ways of reducing water pollution.
Answer: Four effective ways of curbing water pollution are:
- Factory industrial wastewater must be treated in Effluent Treatment Plants (ETP) to neutralize toxic chemicals before discharge into rivers.
- Banning public washing of clothes, utensils, bathing of cattle, and dumping of plastic trash directly into rivers and ponds.
- Treating municipal sewage in Sewage Treatment Plants (STP) before releasing it into water bodies.
- Encouraging farmers to use natural organic manure, compost, and bio-pesticides instead of harmful synthetic chemical fertilizers.
Value-Based Questions
On Ria’s birthday, her grandparents arranged a ‘pooja’ at home. Ria participated with full devotion. Next day, Ria’s parents put the flowers and other materials used in the ‘pooja’ in a polythene bag to immerse them in the holy river running across the city. Ria remembered her science lesson where her teacher had explained the causes of water pollution. She politely shared her thoughts with her parents. Her parents felt happy about their daughter’s environmental concern and did not put the used pooja materials into the river.
1. Why did Ria object to immersing pooja materials in the river?
Answer: Ria understood that polythene bags are non-biodegradable, choke river life, and that dumping heavy organic debris into rivers causes water pollution and degrades water quality.
2. What does the incident tell us about Ria and her parents?
Answer:
– Ria: She is observant, applies textbook knowledge to real-life situations, loves nature, and communicates respectfully with elders.
– Her parents: They are open-minded, receptive to wise advice, supportive, and proud of their child’s moral values.
3. How should floral pooja offerings be disposed of in an eco-friendly manner?
Answer: Used sacred flowers and leaves should be buried in a garden pit to make rich organic compost or used as natural soil mulch, rather than thrown into rivers in plastic bags.
Something to Do
1. River Cleanliness Awareness: Create a small comic strip showing children stopping someone from dumping garbage into a local river, highlighting how clean rivers mean healthy citizens.
2. Crossword Puzzle: Solve keywords: Fertilisers (Down), Rainwater (Across), Typhoid (Down), Cholera (Across) related to water pollution concepts.
Related Chapters:
- DAV Class 4 Science Solutions (All Chapters)
- DAV Class 4 Science Chapter 8 Water Scarcity
- DAV Class 4 Science Chapter 9 Safe Handling and Storage of Water
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