Chapter 8: Pollution
Solved textbook questions with step-by-step explanations.
Grade 8 Q&A: Chapter 8: Pollution
Welcome to the Questions and Answers section for Grade 8 Science, Chapter 8: "Pollution." This chapter covers the definition of pollution and pollutants, various types of pollution (air, water, soil, noise, light, and radioactive), their causes, harmful effects on living beings and the environment, and essential measures for prevention and control.
Important Questions and Answers
Q1: Define 'Pollution' and 'Pollutants'.
Answer: Pollution is the contamination of the environment (air, water, soil) by harmful substances or agents. Pollutants are the harmful substances or agents that cause pollution.
Q2: List the major types of pollution discussed in this chapter.
Answer: The major types of pollution are Air pollution, Water pollution, Soil pollution, Noise pollution, Light pollution, and Radioactive pollution.
Q3: What are the main causes of Air Pollution?
Answer: Main causes of air pollution include burning of fossil fuels (coal, petroleum) in industries, vehicles, and power plants; smoke from factories and vehicles (containing gases like CO, SO₂, NOₓ); use of CFCs; and natural sources like forest fires and volcanic eruptions.
Q4: Explain 'Acid Rain' and its effects.
Answer: Acid Rain occurs when pollutants like sulfur dioxide (SO₂) and nitrogen oxides (NOₓ) from industries and vehicles react with water vapor in the atmosphere to form sulfuric acid and nitric acid. These acids fall to the Earth as rain, damaging buildings (e.g., Taj Mahal), plants, and aquatic life.
Q5: What is 'Global Warming'? How is air pollution related to it?
Answer: Global Warming is the long-term increase in Earth's average surface temperature. Air pollution, particularly the increase in greenhouse gases like carbon dioxide (CO₂) and methane from burning fossil fuels, traps heat in the atmosphere, leading to global warming, melting glaciers, and rising sea levels.
Q6: What is 'Ozone Depletion' and why is it a concern?
Answer: Ozone Depletion is the thinning of the protective ozone layer in the stratosphere, mainly due to chemicals like CFCs. The ozone layer shields Earth from harmful ultraviolet (UV) radiation. Its depletion allows more UV radiation to reach the Earth's surface, increasing risks of skin cancer, cataracts, and harming crops.
Q7: List three ways to prevent Air Pollution.
Answer:
- Use public transport, carpooling, or cycling to reduce vehicular emissions.
- Plant more trees (afforestation).
- Control industrial emissions by using filters and scrubbers.
- Promote the use of cleaner fuels (CNG, LPG) and renewable energy sources.
Q8: What are the major causes of Water Pollution?
Answer: Major causes include discharge of untreated industrial waste and sewage into water bodies, agricultural runoff containing pesticides and fertilizers, oil spills, and dumping of garbage and plastic waste.
Q9: What are the effects of Water Pollution on human health and aquatic life?
Answer: On human health, it causes water-borne diseases (cholera, typhoid, dysentery, hepatitis) and skin diseases. On aquatic life, it harms aquatic plants and animals, disrupts food chains, and can lead to the death of marine life due to oxygen depletion (eutrophication).
Q10: Explain 'Eutrophication'.
Answer: Eutrophication is the process where excessive nutrients (e.g., from agricultural fertilizers) enter water bodies, leading to rapid growth of algae (algal blooms). This dense algal growth blocks sunlight, causes the death of submerged plants, and when algae die and decompose, they deplete oxygen in the water, harming other aquatic organisms.
Q11: How can Water Pollution be prevented?
Answer: Water pollution can be prevented by treating industrial and domestic sewage before discharge, minimizing the use of pesticides and fertilizers, proper disposal of garbage, and avoiding dumping waste into water bodies.
Q12: What are the main causes of Soil Pollution?
Answer: Main causes include improper disposal of industrial waste, domestic garbage, and electronic waste; excessive use of chemical fertilizers and pesticides; deforestation; and open defecation.
Q13: List the effects of Soil Pollution.
Answer: Effects include loss of soil fertility, reduced agricultural yield, contamination of groundwater, entry of harmful chemicals into the food chain, and harm to soil organisms.
Q14: How can Soil Pollution be controlled?
Answer: Soil pollution can be controlled by proper waste management (reduce, reuse, recycle), promoting organic farming, afforestation (planting trees), and safe disposal of hazardous waste.
Q15: Define 'Noise Pollution' and list its causes.
Answer: Noise pollution is excessive or unwanted sound that can cause adverse effects on human health and the environment. Causes include vehicular traffic (horns, engines), industrial machinery, construction activities, loud music, loudspeakers, and firecrackers.
Q16: What are the effects of Noise Pollution on human health?
Answer: Effects on human health include hearing loss, headaches, stress, high blood pressure, sleep disturbance, irritation, and reduced concentration.
Q17: Suggest three measures to prevent Noise Pollution.
Answer:
- Control noise from vehicles and industries by using silencers.
- Plant trees to act as sound barriers.
- Avoid unnecessary use of horns and loudspeakers.
- Create 'silent zones' near hospitals and schools.
Q18: What is 'Light Pollution' and what are its effects?
Answer: Light pollution is excessive, misdirected, or obtrusive artificial light. Its effects include disruption of natural sleep cycles in humans, interference with astronomical observations, disruption of nocturnal animal behavior, and wasting energy.
Q19: How can Light Pollution be reduced?
Answer: Light pollution can be reduced by using shielded light fixtures that direct light downwards, reducing unnecessary outdoor lighting, and using motion sensors and timers for lights.
Q20: What is 'Radioactive Pollution'? List its causes.
Answer: Radioactive pollution is the release of radioactive substances into the environment, causing harm to living organisms. Causes include nuclear power plant accidents, improper disposal of radioactive waste from nuclear reactors, medical facilities, and nuclear weapons testing.
Q21: What are the severe effects of Radioactive Pollution?
Answer: Severe effects include cancer, genetic mutations, birth defects, radiation sickness, and death in humans. It also leads to long-term contamination of soil and water, affecting ecosystems for generations.
Q22: How can Radioactive Pollution be prevented?
Answer: Prevention involves safe disposal of radioactive waste in specially designed, shielded facilities; strict safety regulations in nuclear power plants; and international treaties to ban nuclear weapons testing.
Q23: Why is proper waste management crucial for preventing pollution?
Answer: Proper waste management (reduce, reuse, recycle, proper disposal) is crucial because it prevents the accumulation of waste in landfills, reduces the need for raw materials (thus reducing industrial pollution), and prevents toxic substances from leaching into soil and water, thereby controlling soil and water pollution.
Q24: Explain the concept of '3 R's' in pollution control.
Answer: The '3 R's' stand for Reduce, Reuse, and Recycle.
- Reduce: Minimize the generation of waste.
- Reuse: Use items multiple times instead of discarding them after single use.
- Recycle: Process used materials into new products to prevent waste of potentially useful materials.
Q25: How does afforestation help in controlling air pollution?
Answer: Afforestation (planting trees) helps control air pollution because trees absorb carbon dioxide (a major greenhouse gas) during photosynthesis and release oxygen. They also help filter particulate matter and other pollutants from the air, improving air quality.
Exercise Solutions (From Screenshot Page 61)
Q1: Fill in the blanks.
- The contamination of the environment by harmful substances is called Pollution.
- The harmful substances that cause pollution are called Pollutants.
- The thinning of the ozone layer is caused by CFCs (Chlorofluorocarbons).
- Excessive nutrients in water bodies lead to Eutrophication.
- The major cause of noise pollution is Vehicular traffic.
- The disease caused by excessive UV radiation due to ozone depletion is skin cancer.
- The proper disposal of waste is called waste management.
- The 3 R's of pollution control are Reduce, Reuse, and Recycle.
Q2: Match the pairs.
(Note: As an AI, I cannot create interactive matching. I will provide the correct pairs.)
- Air pollution - Acid rain
- Water pollution - Eutrophication
- Soil pollution - Loss of fertility
- Noise pollution - Hearing loss
- Light pollution - Disruption of sleep cycles
- Radioactive pollution - Genetic mutations
Q3: Give scientific reasons.
- Acid rain is harmful to historical monuments.
Reason: Acid rain contains sulfuric acid and nitric acid, which are formed from air pollutants like sulfur dioxide and nitrogen oxides. These acids react with the calcium carbonate (marble) present in historical monuments, causing them to corrode and lose their luster, leading to damage and discoloration. - Eutrophication leads to the death of aquatic life.
Reason: Eutrophication is caused by excessive nutrients (e.g., from fertilizers) in water, leading to rapid growth of algae (algal bloom). This dense algal layer blocks sunlight, preventing submerged plants from photosynthesizing. When the algae die, decomposers (bacteria) consume them, rapidly depleting the dissolved oxygen in the water. This lack of oxygen suffocates and kills fish and other aquatic organisms. - Noise pollution causes health problems.
Reason: Prolonged exposure to excessive or unwanted sound (noise pollution) can lead to various health problems. It can damage the delicate structures of the inner ear, causing permanent hearing loss. Beyond hearing, it can elevate stress levels, increase blood pressure, disrupt sleep patterns, cause headaches, and lead to irritability, impacting overall well-being. - Planting trees helps to control air pollution.
Reason: Trees play a vital role in controlling air pollution. During photosynthesis, they absorb carbon dioxide, a major greenhouse gas, and release oxygen. They also act as natural filters, trapping particulate matter, dust, and other airborne pollutants on their leaves and branches, thus improving air quality.
Q4: Answer the following questions.
- What are the causes and effects of air pollution?
Answer:- Causes: Burning of fossil fuels (coal, petroleum) in industries, vehicles, power plants; smoke from factories and vehicles (CO, SO₂, NOₓ); use of CFCs; natural sources like forest fires and volcanic eruptions.
- Effects: Respiratory problems (asthma, bronchitis), lung diseases, heart diseases, eye irritation, headaches in humans. Environmental effects include acid rain, global warming, and ozone depletion.
- Explain different types of water pollution.
Answer: Water pollution can be categorized by source:- Industrial Waste: Discharge of untreated chemical effluents from factories into water bodies.
- Domestic Sewage: Untreated wastewater from homes containing organic matter, pathogens, and detergents.
- Agricultural Runoff: Water flowing from agricultural fields carrying excess pesticides, herbicides, and fertilizers into water bodies.
- Oil Spills: Accidental release of crude oil from tankers or drilling operations into oceans.
- Solid Waste Dumping: Direct dumping of garbage, plastics, and other solid waste into rivers, lakes, and oceans.
- What are the effects of soil pollution on human health and the environment?
Answer:- On Human Health: Harmful chemicals from polluted soil can enter the food chain through crops and water, leading to various health problems, including poisoning, cancer, and developmental issues.
- On Environment: Soil pollution leads to a significant loss of soil fertility, reducing agricultural productivity. It can contaminate groundwater through leaching, harm beneficial soil organisms, disrupt nutrient cycles, and contribute to desertification.
- What measures can be taken to control noise pollution?
Answer: Measures to control noise pollution include:- Controlling noise at the source (e.g., using silencers in vehicles and industrial machinery).
- Planting trees along roads and around residential areas, as they act as sound barriers.
- Avoiding unnecessary use of vehicle horns and loudspeakers.
- Implementing strict regulations for industrial noise and construction activities.
- Creating 'silent zones' near sensitive areas like hospitals, schools, and residential complexes.
- Explain the importance of the 3 R's in pollution control.
Answer: The '3 R's' - Reduce, Reuse, and Recycle - are crucial for pollution control:- Reduce: Minimizing the consumption of resources and generation of waste reduces the overall burden on the environment and the need for new production, which often causes pollution.
- Reuse: Using items multiple times instead of discarding them after a single use extends their lifespan, reduces waste, and conserves resources that would otherwise be used to produce new items.
- Recycle: Processing used materials into new products prevents waste from accumulating in landfills, saves energy (as producing from recycled materials often requires less energy than from virgin materials), and conserves natural resources.
Q5: Differentiate between.
- Air Pollution and Water Pollution
Feature Air Pollution Water Pollution Medium Atmosphere (air) Water bodies (rivers, lakes, oceans, groundwater) Main Pollutants Gases (CO, SO₂, NOₓ, CFCs), particulate matter, smoke Industrial waste, sewage, pesticides, fertilizers, oil, plastics Primary Effects Respiratory diseases, acid rain, global warming, ozone depletion Water-borne diseases, harm to aquatic life, eutrophication Prevention Examples Cleaner fuels, public transport, afforestation Wastewater treatment, reduced chemical runoff, proper waste disposal - Soil Pollution and Noise Pollution
Feature Soil Pollution Noise Pollution Medium Soil (land) Sound (air, through vibrations) Main Pollutants Industrial waste, garbage, plastics, pesticides, fertilizers Loud sounds from vehicles, industries, loudspeakers, firecrackers Primary Effects Loss of soil fertility, groundwater contamination, food chain entry of toxins Hearing loss, stress, high blood pressure, sleep disturbance Prevention Examples Proper waste management, organic farming, afforestation Use of silencers, tree planting, avoiding unnecessary loud sounds
References
- Maharashtra State Board Science and Technology Standard Eight Textbook (Specific Edition/Year) - Chapter 8: Pollution.
- Maharashtra State Board 8th Standard Science Syllabus.
- Balbharati Science and Technology Textbook.