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 banner image
author_logo

Written by Team Trustudies
Updated at 2021-04-01


NCERT solutions for class 8 Science Chapter 18 Pollution Of Air And Water Exercise

Q.1 What are the different ways in which water gets contaminated ?



NCERT Solutions for Class 8 Science Chapter 18 Pollution Of Air And Water


Answer :

Water gets contaminated by the addition of :

(i) Agricultural chemicals:

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

(ii) Industrial wastes:

Industries release harmful chemical wastes into water sources without treating those chemicals which results in water pollution.

(iii) Sewage wastes:

Waste materials from kitchens, toilets, and laundry sources are also responsible for contaminating water bodies.

Q.2 At an individual level, how can you help reduce air pollution?



NCERT Solutions for Class 8 Science Chapter 18 Pollution Of Air And Water


Answer :

An individual can reduce air pollution by:

(i) Avoiding the use of cars by using public transport whenever possible.

(ii) Instead of using vehicles, one should prefer walking for short distances.

(iii) By using clean fuels such as LPG and CNG instead of diesel and petrol.

(iv) Always disposing the garbage properly in the garbage bin and trying not to throw or burn the garbage.

(v) Proper treatment of industrial byproducts before releasing it into the air by controlling the emissions of harmful gases.

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



NCERT Solutions for Class 8 Science Chapter 18 Pollution Of Air And Water


Answer :

Clear, transparent water is always fit for drinking.
This statement is not true because clean, transparent water may be free of dust particles and solid solute particles but it may contain harmful chemical materials.

It is also possible that, they may carry disease-causing microorganisms which can cause different water borne diseases like cholera, dysentery, diarrhea, typhoid etc.

Thus, it is always a good step to purify water using different techniques like UV radiation before drinking.

Q.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.



NCERT Solutions for Class 8 Science Chapter 18 Pollution Of Air And Water


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 which should be maintained properly.

(ii) Chemical methods such as chlorination must be used for purifying water on a periodic basis.

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

Q.5 Explain the differences between pure air and polluted air.



NCERT Solutions for Class 8 Science Chapter 18 Pollution Of Air And Water


Answer :

The composition of pure air contains 78% nitrogen, 21% oxygen, 0.03% carbon dioxide and 0.97% other gases. Other gases include methane, argon, ozone and water vapours etc. Pure air is also considered to be free of dust, aerosols and reactive gaseous contaminants of anthropogenic origin.

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. The presence of such substances in the atmosphere are harmful to the health of humans and other living beings and can also cause damage to the climate.

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



NCERT Solutions for Class 8 Science Chapter 18 Pollution Of Air And Water


Answer :

Burning of fossil fuels such as coal and petroleum products releases a variety of pollutants like sulphur dioxide, different oxides of nitrogen into the atmosphere. Vehicular pollution also releases harmful gases and dust particles.

These pollutants react with water vapours present in the atmosphere to form sulphuric acid and nitric acid respectively. These acids come down with the rain, thereby resulting in acid rain.

Effects of acid rain:

(i) Acid rains damage crops.

(ii) Acid rains corrode buildings and monuments especially those which are made up of marbles such as Taj Mahal.

Q.7 Which of the following is not a greenhouse gas?
(a) Carbon dioxide
(b) Sulphur dioxide
(c) Methane
(d) Nitrogen



NCERT Solutions for Class 8 Science Chapter 18 Pollution Of Air And Water


Answer :

(d) Nitrogen is not a greenhouse gas.

EXPLANATION

Carbondioxide is the major greenhouse gas. It traps large amount of heat and thus warms the Earth's atmospheric surface. Methane is also a greenhouse gas and its presence in the atmosphere, affects the Earth's temperature and climate system. Sulphur dioxide is not a direct greenhouse gas like carbon dioxide or methane, but it is considered as an indirect greenhouse gas.

Q.8 Describe the ‘Greenhouse Effect’ in your own words.



NCERT Solutions for Class 8 Science Chapter 18 Pollution Of Air And Water


Answer :

Greenhouse effect in the Earth's atmosphere leads to global warming, i.e., an overall increase in the average temperature of the Earth. Greenhouse effect takes place due to the presence of greenhouse gases. Greenhouse gases includes carbon dioxide, methane, nitrous oxide and ozone. When solar radiations reaches the Earth surface, some of these radiations are absorbed by earth while some radiations are released back to the atmosphere. Greenhouse gases present in the atmosphere trap these radiations and do not allow the heat to leave the atmospheric surface. Though this helps in keeping our planet warm and helps in human survival, but an indiscriminate increase in the amount of greenhouse gases can lead to excessive increase in the Earth's temperature leading to global warming.

Q.9 Prepare a brief speech on global warming. You have to deliver the speech in your class.



NCERT Solutions for Class 8 Science Chapter 18 Pollution Of Air And Water


Answer :

Global warming is an increase in the average temperature of the Earth's surface. It takes place as a result of an increased concentration of greenhouse gases in the atmosphere.

The greenhouse gases include carbon dioxide, methane, nitrous oxide and ozone. These gases trap solar radiations or the heat released by the Earth. Sometimes this helps in keeping our planet warm and helps in human survival.

However, an increase in the amount of greenhouse gases can lead to an increase in the Earth's temperature, thus leading to global warming.

Q.10 Describe the threat to the beauty of the Taj Mahal.



NCERT Solutions for Class 8 Science Chapter 18 Pollution Of Air And Water


Answer :

Acid rain is a major threat to the beauty of the Taj Mahal.

Rainwater is the purest form of water but when it passes through the air to reach the ground, many dust particles and harmful gases like oxides of nitrogen, sulphur dioxide etc., mixes with the rainwater, thus making it acidic in nature.

When acid rain falls on the monument which is completely made up of marble, they react with the components of marbles to form a powder-like substance and this is then washed away by the rain. This phenomenon is known as marble cancer.

The soot particles emitted from the Mathura oil refinery located near Agra is leading to the yellowing of the marble.

Q.11 Why does the increased level of nutrients in the water affect the survival of aquatic organisms?



NCERT Solutions for Class 8 Science Chapter 18 Pollution Of Air And Water


Answer :

An increase in the level of nutrients in water body leads to an excessive increase in the population of algae in the water body.

When these algae die, they serve as a food material for the decomposers and this process utilizes a lot of oxygen which consequently leads to a decrease in the level of dissolved oxygen in the water body.

Hence this increases the mortality rate of fishes, aquatic plants and animals due to the shortage of dissolved oxygen.



FAQs Related to NCERT Solutions for Class 8 Science Chapter 18 Pollution Of Air And Water
There are total 11 questions present in ncert solutions for class 8 science chapter 18 pollution of air and water
There are total 0 long question/answers in ncert solutions for class 8 science chapter 18 pollution of air and water
There are total 1 exercise present in ncert solutions for class 8 science chapter 18 pollution of air and water
Get it on Google Play

Download Trustudies app to get complete NCERT solutions for class 6 - 10