STD-4, CHAPTER-10: WATER POLLUTION, EXTRA QUESTION ANSWERS

 1.      ‘Water is an important natural resource.’- justify this statement.

Ans: i) Water is essential for all living beings.

ii) It is a habitat for many plants aand animals.

iii) It is essential for the existence and survival of all plants and animals.

Thus, water is an important natural resource.

2.      Name the major source of water?

Ans: Rain is the major source of water.

3.      ______ is the purest form of water.

Ans: Rain water (when just formed)

4.      How does the rain water become impure?

Ans: As the rain water reaches the surface of the earth, it dissolves some harmful gases, dust, smoke particles and germs present in air. Thus, it gets impure.

5.      Name any two materials which can make rain water impure.

Ans: Dust and smoke particles which can make rain water impure.

6.      Define the term polluted water.

Ans: Water containing impurities is called polluted water.

7.      What is pollution of water?

Ans: The processes, which make water impure, result in pollution of water.

8.      State the human activities which can cause water pollution.

Ans: i) People wash their clothes and bathe in river water. Some people bathe their cattle in rivers.

ii) People throw domestic waste in rivers.

iii) Waste materials, and harmful chemicals from factories, are often dumped in river water.

iv) Solid waste material, from power plants, may be thrown into the river water.

v) Water, from drains and sewage, goes into rivers.

vi) The chemical fertilisers flow into lakes or rivers after getting mixed with rain water.

vii) Oil, spilled by tankers and oil wells, pollutes sea water.

9.      Which two pollutants are often dumped by the factories into the rivers?

Ans: Harmful chemicals and waste materials are often dumped by the factories into the rivers.

10.  State the effects of water pollution.

Ans: i) Poisonous chemicals, from factories, kill marine animals.

ii) Industrial, and agricultural, wastes increase the growth of micro-organisms in water. This can reduce the supply of oxygen for the aquatic animals.

iii) Aquatic plants and animals get infected by polluted water. When other animals eat these infected animals or plants, they also become sick.

iv) Drinking polluted water may cause diseases.

v) Using polluted water for irrigation, decreases the fertility of the soil and damages crops.

11.  Suggest some ways to reduce water pollution.

Ans: i) Wastes from factories and power houses should not be allowed to flow into rivers directly.

ii) Pipes, carrying sewage, should not be allowed to enter into wells or rivers.

iii) Water, from drains or sewage, should not be allowed to enter into wells or rivers.

iv) People should not wash clothes, or use soaps if they bathe, in rivers.

v) The use of chemical fertilisers should be minimised. Instead, natural manure should be used.

STD-4: CHAPTER-9: METHODS OF SAFE-HANDLING OF WATER: EXTRA QUESTION-ANSWERS

 1.      Why does our body need water?

Ans: i) Water is needed for proper functioning of our body.

ii) Our body needs water for digestion of food and for removal of wastes from the body.

2.      We need to drink _______ glasses of water everyday.

Ans: We need to drink eight to ten glasses of water everyday.

3.      Define potable water.

Ans: Water, which is clean and fit for drinking, is called potable water.

4.      State two methods of drawing ground water.

Ans: Ground water can be drawn from wells or by using hand pumps.

5.      What are germs?

Ans: Germs are extremely small living beings which can cause diseases.

6.      Name the diseases that can be caused by drinking unclean water.

Ans: Jaundice, diarrhea, dysentery and cholera can be caused by drinking unclean water.

7.      Why should water be purified before drinking?

Ans: Drinking unclean water can cause diseases, as they contain dirt and germs. So, water should be purified before drinking.

8.      State three methods of purifying water.

Ans: Three methods to purify water are, i) Boiling,  ii) Filtration,  iii) Chlorination

9.      How does boiling help in making water safer for drinking?

Ans: Boiling kills the germs present in water. Thus, boiling helps in making water safer for drinking.

10.  What is filtration?

Ans: Filtration is a method for removing dust and other suspended particles from water.

11.  How can traditionally water be purified?

Ans:i) We can filter water through a clean, thin cloth.

ii) We can also use a traditional filter containing sand and gravel.

12.  How filtration method is useful?

Ans: Filtration removes dust and other suspended particles from water.

13.  What is drawback (demerit) of filtration method?

Ans: Filtration method does not remove germs.

14.  Why is the traditional method of filtration not completely sufficient for making water fit for drinking?

Ans: i) Traditional method of filtration removes dust and other suspended particles from water.

ii) But, this method does not remove germs.

So, traditional method of filtration is not completely sufficient for making water fit for drinking.

15.  What is the difference between traditional filters and modern filters?

(OR) How modern filters are more useful than traditional filters?

(OR) What is the advantage of modern filters over traditional filters?

       Ans: i) Traditional filters does not remove germs. For removing germs, water should be boiled after filtration.

ii) But, modern filters remove germs along with dirt and dust. Water filtered by such filters can be directly used for drinking.

So, modern filters are more useful than traditional filters.

16.  What is chlorination? How does it purify water?

Ans: i) Adding a correct small amount of chlorine in filtered water, is called chlorination.

ii) Chlorination kills germs and makes it fit for drinking.

17.  What is stagnant water?

Ans: Standing water or still water is called as stagnant water.

18.  Why should we not allow water to stagnate around our houses?

Ans: i) Dirty and stagnant water is a major cause of diseases.

ii) Stagnant water is a breeding place for mosquitoes.

So, we should not allow water to stagnate around our houses.

19.  Name some places where water can stagnate.

Ans: Water can stagnate in old or broken containers, in room coolers, in flower pots etc.

20.  Name the diseases which are spread by mosquitoes.

Ans: Malaria, dengue and chikungunya are spread by mosquitoes.

21.  State two ways that can be used to prevent breeding of mosquitoes in room coolers.

Ans: We can adopt the following measures to prevent the breeding of mosquitoes in room coolers,        i) We should change water in room coolers after every 3-4 days.

ii) When water in room coolers cannot be changed, two spoons of kerosene should be put in it.

22.  Which substances are used for making containers of water?

Ans: Copper, brass, steel and plastics are used for making water containers.

23.  Why proper storage and safe handling of water is important?

Ans: Proper storage, and safe handling, of purified water is very important to keep the germs away.

24.  State the ways of safe handling of drinking water.

Ans: Some ways of proper storage and safe handling of water are,

i) Water should always be stored in clean and covered containers.

ii) We should never dip our hands in water stored for drinking purpose.

iii) We should use a ‘ladle’, or some other clean utensil, to take out water from a container.

iv) We should not drink water that has been stored for many days.

STD-3, CHAPTER-7: BIRDS AND THEIR NESTS, EXTRA QUESTION-ANSWERS

1.      Why are birds called as ‘aerial animals’?

Ans: Birds can fly in air. So, they are called aerial animals.

2.      Write the special features of birds that help them to fly.

Ans: Birds can fly in air, because they have,

i)   Hollow bones, which make their body light.

ii) Wings that are made up of light feathers.

iii)  Pointed, sharp, boat shaped body.

iv)  Tail, which helps them while changing the direction.

3.      Name some birds which cannot fly.

Ans: Penguin, ostrich, kiwi, are some birds which cannot fly. (others are, Steamer duck, Weka, Kakapo,  Takahe and Cassowary)

4.      Why are birds very light in weight?

Ans: Birds are very light in weight because their body is made up of hollow bones.

5.      Why penguin and some other birds cannot fly?

Ans: As penguins and some other birds have quite heavy bodies, so they cannot fly.

6.      How do the birds use their beaks and claws?

Ans: Birds use their beaks and claws to catch food and to build their nests.

7.      There are about ______ kinds of birds.

Ans: 10,000

8.      Name the smallest bird.

Ans: Humming bird is the smallest bird.

9.      Name the largest bird.

Ans: Ostrich is the largest bird.

10.  What is a nest?

Ans: A nest is a bird’s home.

11.  List some places where we find birds’ nests.

Ans: We find birds’ nests on trees, on the terraces of buildings, on electricity poles, on the top of almirah, behind the shelf, in the meter room and many other places.

12.  List some materials used by various birds to make their nests.

Ans: Different things like twigs, straws, leaves, feathers, cotton, small paper-bits, mud, wires and small wooden pieces, are used by various birds to make their nests.

13.  How are nests useful for birds?

Ans: i) Nests protect the birds from enemies and bad weather.

ii) Birds lay their eggs and hatch them in the nests.

iii) Birds keep their young ones safe and warm in their nests. The chicks stay there, till they are old enough to fly.

14.  Why do birds make sounds?

Ans: Birds make sounds,

                                          i)  to communicate about danger, food and

                                          ii) to locate one another.

15.  Birds start making their nests usually in the month of-

Ans: April

16.  Birds are very busy during the month of _____.

Ans: April

17.  Name three birds who work in pairs to make their nests.

Ans: The sparrow, sunbird and dove work in pairs to make their nests.

18.  Where can we find a sparrow’s nest?

Ans: We can find a sparrow’s nest, between the branches of a tree, on the top of almirah, behind the shelf, in the meter room or any other such corner.

19.  Name the materials used by a crow to make its nest.

Ans: A crow uses all types of material, like wires and small wooden pieces, to make its nest.

20.  Where does the crow build its nest?

Ans: The crow builds its nest on, or near, the topmost branches of a tree.

21.  How does a tailor bird make its nest?

Ans: i) A tailor bird stitches the leaves with the help of its beak using small twigs as thread to make its nest.

ii) It uses straws, soft twigs and feathers, inside the nest, to make a cushion.

22.  Which bird makes a tuk-tuk sound, while making its nest in a tree trunk?

Ans: A barbet or a coppersmith, makes tuk-tuk sound, while making its nest in a tree trunk.

23.  When, and where, does a barbet make its nest?

Ans: In summers, a barbet makes its nest in the holes of tree trunk.

24.  Name the materials used by the sunbird to make its nest.

Ans: The sunbird uses plant fibres, grass, spiderweb and feathers for making its nests.

25.  How the nesting habit of weaver bird is different from other birds?

Ans: i) In case of weaver birds, it is the male who weaves the nest.

ii) The male bird weaves the nest beautifully in different shapes.

iii) The female bird chooses a nest where she feels most comfortable.

26.  Name the materials used by penguins to make their nest.

Ans: Penguins make their nest by using stones and pebbles.

27.  Why the penguin uses stones and pebbles to make its nest?

Ans:i) Penguins live in very cold places.

ii) It is difficult to find twigs, grass, or straw in such places.

iii) So, the penguins collect stones and pebbles to make their nests.  

28.  Name the bird who sings sweetly.

Ans: Koel sings sweetly.

29.  Name the bird which does not make its nest.

Ans: Koel does not make its nest.

30.  Where does the koel lay its egg?

Ans: The koel lays its eggs in the crow’s nest.

31.  What happens to the eggs laid by the koel in the crow’s nest?

Ans: The crow hatches the koel’s eggs along with its own eggs.

32.  “The birds have a challenging job.”- Justify this statement.

Ans:i) At times, some animals like cats, rats and other large birds break the nest of the bird.

ii) Thus, the birds have a challenging job to protect their eggs and young ones.

33.  Why we should not break the nests of birds?

Ans: i) Making a nest is a time-consuming task.

ii) Also, the birds have a challenging job to protect their eggs and young ones from enemies and weather. So, we should not break the nests of birds.

34.  What do you mean by migration?

Ans: Moving from one place to another is called as migration.

35.  Describe the causes of migration of birds. (OR)  Why do birds migrate?

Ans: Birds migrate from one place to another,

i)         To search food

ii)       To protect themselves from extreme cold.

iii)     To escape their enemies.

36.  Name some migratory birds.  (OR) Name the birds who migrate to India during winters.

Ans: Siberian crane, painted stork, flamingo, rosypelican, migrate to India during winters.

37.  When do the migratory birds return to their cooler homes?

Ans: The migratory birds return to their cooler homes when summer starts.

38.  Name the bird who travels a distance of 1,76,000 kilometres, from the Arctic region to the Antarctic region.

Ans: The arctic tern

39.  Name region which is the natural home of the Arctic tern.

Ans: The Arctic region is the natural home of the Arctic tern.

STD-5, CHAPTER- 9:FUELS, EXTRA QUESTION ANSWERS

1.      What is a fuel?

Ans: A substance that produces energy on burning is called a fuel.

2.      State the main function of a fuel.

Ans: The main function of a fuel is to produce energy on burning.

3.      Name the types of fuel.

Ans: Fuels are available in solid, liquid or gaseous forms.

4.      Give some examples of solid fuels.

Ans: Wood, coal, coke and cowdung are some examples of solid fuels.

5.      Give some examples of liquid fuels.

Ans: Kerosene, petrol and diesel are some examples of liquid fuels.

6.      Name some gaseous fuels.

Ans: LPG, CNG, PNG and biogas are examples of gaseous fuels.

7.      LPG stands for _______.

Ans: Liquefied petroleum Gas

8.      CNG stands for _______.

Ans: Compressed Natural Gas

9.      PNG stands for ______.

Ans: Piped Natural Gas

10.  Why do we need energy?

Ans: We need energy for cooking, for movement of trains, automobiles and aeroplanes, for generating electricity, for running various machines and so on.

11.  Name some domestic fuels.

Ans: Wood, cowdung cakes, coal, kerosene, LPG, PNG and biogas are some domestic fuels.

12.   Why is biogas regarded as a better fuel than cowdung cakes?

Ans: i) Cowdung cakes produce smoke whose concentration can be as much as five times higher than that produced by ordinary coal.

ii) Biogas, on the other hand, does not produce smoke and are more efficient. They are eco-friendly. Thus, they are regarded as a better fuel than cowdung cakes.

13.  How can we use the ash, obtained by burning coal?

Ans: The ash, a by-product of coal combustion, is used as a filler for things like the tennis rackets and golf balls.

14.  Name some cleaner fuels. Why are they named so?

Ans: i) LPG, CNG, PNG and biogas are cleaner fuels.

ii) They are named so, because they do not produce smoke on burning and do not leave any ash after burning.

15.  How the modern trains different from earlier trains?

Ans:i) Earlier, trains were run with the help of steam engines. In these engines, steam was produced by burning coal.

ii) Now-a-days, train engines use either electricity or diesel.

16.  Vehicles, like buses, cars and scooters run on ______.

Ans: Petrol or diesel

17.  Aeroplanes commonly use a highly refined kerosene based fuel known as _____.

Ans: Aviation Turbine Fuel (ATF).

18.  Why is CNG called a better green fuel?

Ans:i) CNG do not produce smoke on burning and do not leave any ash after burning.

ii) CNG powered vehicles have lower maintenance costs and better efficiency.

iii) It causes less air pollution, is more eco-friendly and causes less harm to the health of humans and animals.

Therefore, CNG is called a better green fuel.

19.  How is coal used by powerhouses for generating electricity?

Ans:i) Powerhouses often burn coal to convert water into steam.

ii) This steam energy is used to operate turbines which in turn, help to generate electricity.

20.  What are the modern methods of producing electricity/

Ans: Electricity is now being produced by using the energy stored in water and also by using wind energy and energy of the sun.

21.  Petrol, diesel and kerosene are all obtained by refining _______.

Ans: Crude oil (petroleum)

22.   What are fossil fuels?

Ans: Fuels which are formed from decomposition of living things over a period of millions of years.

23.  Name the three main fossil fuels.

Ans: Coal, crude oil (petroleum) and natural gases are the three main fossil fuels.

24.  How have fossil fuels been formed?

Ans: i) Fossil fuels are formed by decomposition of animal and plant matter, buried deep under the surface of earth, at high temperature and pressure prevailing there.

ii) Over a period of millions of years, these animal and plant matter got changed into fossil fuels.

25.  Describe the three main fossil fuels.

Ans: The three main natural fossil fuels are, coal, crude oil (petroleum) and natural gas.

i) Coal- It is a combustible black sedimentary rock. It is primarily used for production of heat and electricity.

ii) Crude oil (petroleum) – This was formed from dead sea-creatures. These dead sea-creatures fell to the sea-bed where their bodies underwent chemical changes due to bacteria.

iii) Natural Gas- This was formed in the same way as crude oil. It is often collected when drilling for oil.

26.  When is a source of energy said to be a renewable source of energy? Give some examples of such sources.

Ans: The sources of energy which is freely available and which can be readily replenished, are said to be a renewable source of energy. Examples of renewable sources of energy are, Solar energy, tidal energy, wind and biomass.

27.  Define biomass.

Ans: The waste matter of animals and plants are called biomass.

28.  When a source of energy said to be a non-renewable source of energy? Give two examples of such sources.

Ans: Sources of energy, which once used, cannot be readily replenished are called non-renewable sources of energy.

ii) Coal and petroleum are two of the non-renewable sources of energy.

29.  Define Hydroelectricity.

Ans: Electricity, generated by using the energy of water, is called hydroelectricity.

30.  State two disadvantages of fossil fuels.

Ans: i) Fossil fuels are non-renewable sources of energy.

ii) They are also a major cause of environmental pollution.

31.  Why should efforts need to be made to reduce the use of fossil fuels?

Ans: i) Fossil fuels are available in limited quantity and are not likely to last for a long time.

ii) They are also a major cause of environmental pollution.

We should, therefore, make efforts to reduce the use of fossil fuels.