NCERT Solutions for Class 8 Science Chapter 18 Pollution of Air and water

NCERT Solutions for Class 8 Science Chapter 18 Pollution of Air and water are given below. Here we have provided the best and error-free answers to all the exercise questions that will strengthen your foundation in science. Solving NCERT questions will assist you in grasping the content in the Crop Production and Management chapter in a better way.

In these solutions, we have answered all the intext and exercise questions provided in NCERT class 8 science textbook. NCERT Solutions for Class 8 Science Chapter 18 Pollution of Air and water provided in this article are strictly based on the CBSE syllabus and curriculum. Students can easily download these solutions in PDF format for free or can read them online.

Pollution of Air and water Class 8 Science NCERT Solutions

Exercise Questions

Question 1: What are the different ways in which water gets contaminated?

Answer: Water gets contaminated by the addition of:

(i) Agricultural chemicals: Farmers use excessive amounts of pesticides and fertilizers to increase crop production. These chemicals get carried away to the water bodies due to rains and floods which lead to water pollution.

(ii) Industrial wastes: Industries release harmful chemical wastes into water sources, thereby polluting them.

(iii) Sewage wastes: Waste materials from kitchens, toilets, and laundry sources are also responsible for contaminating water.

Question 2: At an individual level, how can you help reduce air pollution?

Answer: Air pollution should be checked at individual level:

  • At an individual level, we can plant trees as trees reduce air pollution.
  • We can use public transportation and encourage carpooling so that air pollution can be reduced.
  • Instead of going by cars and scooters for short distances, we can go by foot or by bicycles.
  • By saying no to crackers we can minimise air pollution as well as noise pollution.
  • We should not burn garbage and dry leaves. The burning of dry leaves and garbage release greenhouse gases which are responsible for global warming.

Question 3: Clear, transparent water is always fit for drinking. Comment.

Answer: No, this is not true that clean, transparent water is always fit for drinking. It is possible that they may carry disease-causing microorganisms. Thus, it is good to purify water before drinking.

Question 4: You are a member of the municipal body of your town.

Make a list of measures that would help your town to ensure the supply of clean water to all its residents.

Answer: To ensure the supply of clean water to all residents the following steps must be taken:

(i) The main water source must be built-in clean surroundings and should be maintained properly.

(ii) Chemical methods such as chlorination must be used for purifying water.

(iii) The area around water pipes must also be clean.

Question 5: Explain the differences between pure air and polluted air.

Answer: The composition of pure air contains 78% nitrogen, 21% oxygen and 0.03% carbon dioxide. Besides these, there are some other gases like methane, argon, ozone and water vapours’. The air is said to be polluted when the composition of air is altered by the addition of harmful substances or gases such as sulphur dioxide, carbon monoxide, nitrogen dioxide and particulate matter.

Question 6: Explain circumstances leading to acid rain. How does acid rain affect us?

Answer: When harmful gases like sulphur dioxide and nitrogen dioxide, react with the water vapour present in the atmosphere to form sulphuric acid and nitric acid. The acids drop down with rain, making the rain acidic. This is called acid rain.

Acid rain causes skin irritation, inhibits germination of plants, causes corrosion to bridges and building. It changes the fertility of the soil, destroys plants and aquatic life.

Question 7: Which of the following is not a greenhouse gas?

(a) Carbon dioxide
(b) Sulphur dioxide
(c) Methane
(d) Nitrogen

Answer: (d) Nitrogen

Question 8: Describe the ‘Green House Effect’ in your own words.

Answer: Basically, the greenhouse effect means warming of the earth’s environment. When the sun’s ray falls on earth, a part of the radiation that falls on the earth is absorbed by it and a part is reflected back into space. Greenhouse gases present in the atmosphere trap these radiations and do not allow heat to leave. This helps in keeping our planet warm and thus helps in survival. CO2, methane and CO are the gases responsible for this effect.

Question 9: Prepare a brief speech on global warming that you have to make in your class.

Answer: Global warming is an increase in the average temperature of the Earth’s surface. It occurs as a result of an increased concentration of greenhouse gases in the atmosphere. The greenhouse gases include carbon dioxide, methane, and water vapour. These gases trap solar radiations released back by the Earth. This helps in keeping our planet warm and thus, helps in human survival. However, an increase in the amount of greenhouse gases can lead to an increase in the Earth’s temperature leading to global warming.

Question 10: Describe the threat to the beauty of the Taj Mahal.

Answer: Due to increase of gases like sulphur dioxide and nitrogen dioxide, acid rain take place. Acid rain corrodes the marble of the monument. The phenomenon is also called “Marble cancer”. Suspended particulate matter, such as the soot particles emitted by Mathura oil refinery, has contributed towards yellowing of the marble.

Question 11: Why does the increased level of nutrients in the water affect the survival of aquatic organisms?

Answer: Excessive quantities of chemicals (fertilizers, weedicides, pesticides etc.) washed from the fields enter into ponds. These act as nutrients for algae to flourish. Once these algae die, they serve as food for decomposers like bacteria. In this process a lot of oxygen in these ponds gets used up. This results in a decrease in the oxygen level, which kills aquatic organisms.

NCERT Solutions for Class 8 Science Chapter 18 – A Brief Discussion

CBSE Class 8 Science NCERT Solutions Chapter 18 helps students to clear their doubts and to score good marks in the board exam. All the questions are solved by experts with a detailed explanation that will help students complete their assignments & homework. Having a good grasp over CBSE NCERT Solutions for Class 8 Science will further help the students in their preparation for board exams and other competitive exams such as NTSE, Olympiad, etc.

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