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.