Pollution of Air and Water Textbook Questions
Question 1.
What are the different ways in which water gets contaminated?
Answer:
Following are the ways by which water gets contaminated:
People dispose of garbage in the water.
Many industries discharge their harmful chemicals directly into rivers
and streams.
Chemical fertilisers, pesticides and weedicides used in agricultural
practices get dissolve in water and are washed away into water bodies
from the fields.
Untreated sewage is directly discharged into water from household
activities.
Question 2.
At an individual level, how can you help to reduce air pollution?
Answer:
I can do the following things to reduce air pollution:
I will use public transport as far as possible.
I will generate awareness among people to reduce air pollution.
I will plant more and more trees because trees help to keep the
environment clean and reduce air 1 pollution.
I will not use vehicles for short distances.
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:
These are the measures that would help our town to ensure the supply of clean
water to all its residents:
Chlorine tablets should be made available.
Proper cleaning of the water tank from time to time.
The water supply pipes should not come in contact with the sewage
pipes.
Question 5.
Explain the differences between pure air and polluted air.
Answer:
Pure air contains 78% nitrogen, 21% oxygen and 0.03% C02. Other gases such as
argon, methane, neon, water vapour, etc. are also found in small quantities. When
this air is contaminated by unwanted substances which have harmful effect on both
living and non-living things like nitrogen oxide, sulphur oxide, carbon monoxide, etc.,
is said to be polluted.
Question 6.
Explain circumstances leading to acid rain. How does acid rain affect us?
Answer:
Nitrogen dioxide, sulphur dioxides are the pollutants which react with the water
vapour present in atmosphere to form sulphuric acid and nitric acid. These acids
come down with the rain, making the rain acidic. This is called acid rain.
Following are the affects of acid rain:
It increases corrosion of metals.
It damages buildings and sculptural materials.
It removes the basic nutrients such as calcium from the soil.
It causes direct damage to plants and crops.
It causes skin eruptions in human being.
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 ‘Greenhouse 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. You have to deliver the speech in your
class.
Answer:
Good Morning,
Respected teacher and my dear friends,
As we all know the continuous increase in the temperature of earth is called global
warming. Global warming is basically caused by pollution of air, excessive heat
which is trapped by the greenhouse gases. Global warming is a threat to life as it
causes a lot of health problems. We may have to face dire consequences due to
global warming.
That’s all friends. Thank you for the attention. Have a good day.
Question 10.
Describe the threat to the beauty of the Taj Mahal.
Answer:
Taj Mahal has become a matter of concern due to pollutants in air that are
discolouring its white marble. Acid rains due to increasing air pollution has started
corroding the marble. Suspended particulate matter, such as the soot particles
emitted by Mathura oil refinery, has contributed towards the yellowing of the marble.
Thus making Taj Mahal losing its beauty.
Question 11.
Why does the increased level of nutrients in the water affect the survival of aquatic
organisms?
Answer:
Increased level of nutrients in the water affect the survival of aquatic organisms as
these act as nutrients for algae to flourish and once these algae die, they serve as
food for decomposers like bacteria and a huge amount of oxygen in water body gets
used up. This results in decrease in the oxygen level, which may kill aquatic
organisms.
Pollution of Air and Water Class 8 Science NCERT Intext
Activities Solved
Activity 1 (NCERT Textbook, Page 239)
You may have covered your nose while passing a brick kiln emitting smoke or started
coughing while walking on a busy road (Fig. 18.1).
On the basis of your experience, compare the quality of air at the places given below:
A park and a busy road.
A residential area and an industrial area.
A busy traffic intersection at different times of the day, e.g., early morning, afternoon
and evening.
A village and a town.
Solution:
When we visit a park we find it full of fresh air and in a busy road we find it polluted
due to fumes, smoke, dust and sound.
An industrial area is more polluted as compared to residential area as industrial area
gets polluted with chemical pollutants, toxic gases, etc.
Air Pollutants Sources Effects
1. CO2 Vehicles, Industries Suffocation, global warm
Carbon monoxide poison
2. Carbon monoxide Vehicles, Industries
global warming
3. Chlorofluorocarbons Refrigerators, air Depletion of the ozone la
conditioners aerosols,
sprays, etc.
Petroleum refineries,
4. Nitrogen oxide Acid rain
agricultural activities
Combustion of fuels,
5. Sulphur oxide Lung damage, acid rain
industries
In early morning there is iess pollution but in afternoon it becomes a little more polluted than
morning and in the evening it becomes extremely polluted.
A town is more polluted than a village.
Activity 2 (NCERT Textbook, Page 240)
You might have read in the newspapers that respiratory problems amongst children
are rising day by day. Conduct a survey of households in your neighbourhood and
among friends to find out how many children are suffering from respiratory
problems.
Solution:
Do it yourself.
Activity 3 (NCERT Textbook, Page 241)
Prepare a table using the pollutants mentioned above (See NCERT textbook at page
241). You may even add more data to the following Table.
Solution:
Activity 4 (NCERT Textbook, Page244)
You have various options of commuting to your school such as walking, going by
bicycle, travelling by bus or other public transport, using a car individually, travelling
by carpool. Discuss in your class the impact of each of these options on the quality
of air.
Solution:
Ways of commuting to school Effect on air pollution
1. Walking No air pollution
2. Going by bicycle No air pollution
3. Travelling by bus or other public transport Decreases air pollution as buses run on CNG.
It increases air pollution as increased number
4. Using a car individually
vehicles will cause more pollution.
5. Travelling by carpool It decreases air pollution.
Activity 5 (NCERT Textbook, Page 245)
Try to collect samples of water from a tap, pond, river, well and lake. Pour each into
separate glass containers. Compare these for smell, acidity and colour. Complete
the following Table.
Solution:
Smell Acidity Colour
Tap Water No smell No Colourless
Pond Water Very smelly Yes Muddy
River Water Little smell Yes Colourless to little mudd
Well Water No smell No Colourless
Lake Water No smell No Colourless
Recall Activity 6 (NCERT Textbook, Page 247)
You had investigated the sewage disposal system of your locality in Class VII. Do
you remember how the sewage was collected from your home and where it went
thereafter?
Solution:
The underground network of small and big pipes called sewers carries the sewage
from the point of production to the point of disposal, i.e., treatment plant.
Activity 7 (NCERT Textbook, Page 247)
Let us construct a water filter with simple, everyday materials.
Take a plastic bottle and cut it into 2 halves at the centre. Use the upper half as a
funnel by putting it upside down in the lower half. Make layers in it with paper napkin
or a fine cloth followed by, cotton, sand and then gravel. Now pour dirty water
through the filter and observe the filtered water.
Discuss the following questions amongst yourselves and with your teacher:
Why do we need to filter water before drinking?
Where do you get your drinking water from?
What will happen if we drink polluted water?
Solution:
Water which is full of dust particles and impurities is unfit for human health thus we
need to filter water before drinking it.
We get drinking water from government supply water or hand pump.
Polluted water have disease-carrying microorganisms and dissolved impurities
which can make us seriously ill.
Activity 8 (NCERT Textbook, Page 248)
Investigate the level of awareness about water pollution in your area. Col-lect data on
the sources of drinking water and the methods of sewage disposal.
What are the common water-borne diseases in the community? You can consult your
local doctor/health worker for this. Which are the governmental and non-
governmental organisations working in this field? What are the measures being
taken by them for generating awareness?
Solution:
Do it yourself.
