Chapter 5 : Coal and Petroleum

Extra Internal Question and Answer:

Question: What are inexhaustible natural resources? Give examples.

Answer: Inexhaustible natural resources are those resources which are present in unlimited quantity in nature and are not likely to be finished by human activities. These resources are continuously available and can be used again and again. Examples: Sunlight, air, and wind.

Question: What are Exhaustible Natural Resources? Give examples.

Answer: Exhaustible natural resources are those resources which are present in limited quantity in nature and can get finished if we use them continuously. These resources take a very long time to form, so they cannot be replaced quickly. Examples of exhaustible natural resources are coal, petroleum, natural gas, forests and minerals.

Question: Write the difference between CNG and LPG as fuels.

Answer: The difference between CNG and LPG as fuels are :

CNG (Compressed Natural Gas)	LPG (Liquefied Petroleum Gas)
It is mainly composed of methane.	It is mainly composed of propane and butane.
It is stored under high pressure in cylinders.	It is stored as a liquid in cylinders.
It is mainly used as a fuel in vehicles like cars and buses.	It is mainly used as a cooking fuel in homes.
It causes very less air pollution.	It also causes less pollution, but slightly more than CNG.

Question: Which fuel is known as a clean fuel?

Answer: CNG (Compressed Natural Gas) and LPG (Liquefied Petroleum Gas) are known as clean fuels because they burn completely and produce very little smoke and harmful gases, thus causing less air pollution.

Question: Why are CNG and LPG called clean fuels?

Answer: CNG and LPG are called clean fuels because they burn completely and produce very little smoke and harmful gases. They do not leave behind any solid residue like ash. Due to this, they cause less air pollution and are safer for the environment compared to other fuels like coal and petrol.

Question: What are fossil fuels? Give examples.

Answer: Fossil fuels are the natural fuels formed from the dead remains of plants and animals buried under the earth millions of years ago. Due to high pressure and temperature over a long period of time, these remains get converted into fuels. Examples: Coal, petroleum and natural gas.

Question: What is petroleum? Where is petroleum found? Name any one product of petroleum.

Answer: Petroleum is a dark, oily liquid found deep inside the earth. It is a fossil fuel formed from the remains of dead plants and animals over millions of years.
Petroleum is found trapped between layers of rocks under the earth’s surface and below the sea bed. It is taken out by drilling wells.
One product of petroleum is petrol.

Question: How is petroleum formed ?

Answer: Petroleum was formed from the dead remains of tiny plants and animals living in the sea millions of years ago. Their bodies got buried under layers of sand and clay. Over a long time, due to high temperature and pressure, these remains were converted into petroleum.

Question: Why is petroleum called a fossil fuel ?

Answer: Petroleum is called a fossil fuel because it is formed from the buried remains of tiny plants and animals that lived in the sea millions of years ago. Due to heat and pressure over a long time, these remains changed into petroleum. Hence, it is known as a fossil fuel.

Question: What is coal gas? How is coal gas obtained? Where is coal gas used?

Answer: Coal gas is a gaseous fuel obtained during the processing of coal. It is mainly a mixture of gases like hydrogen, methane and carbon monoxide.

Coal gas is obtained by the process of destructive distillation of coal. In this process, coal is heated strongly in the absence of air. As a result, different products like coke, coal tar and coal gas are formed.

Coal gas is used as a fuel in many industries. Earlier, it was also used for street lighting, but nowadays its use is mainly limited to industrial purposes.

Question: What is coke?How is coke obtained? Write any two properties of coke.

Answer: Coke is a tough, porous and black substance. It is almost a pure form of carbon.

Coke is obtained from coal by the process of destructive distillation. In this process, coal is heated strongly in the absence of air.

Properties of coke:

(i) It is a hard and porous substance.

(ii) It is almost pure carbon and burns with very little smoke.

Question: Why is coal tar called a complex mixture?

Answer: Coal tar is called a complex mixture because it contains a large number of different substances mixed together. It is made up of many chemicals, each having different properties and uses. These substances cannot be easily separated, so it is known as a complex mixture.

Question: What is coal tar? How is coal tar obtained? Write any two uses of coal tar.

Answer: Coal tar is a thick, black liquid with an unpleasant smell. It is a mixture of many different substances.

Coal tar is obtained during the process of destructive distillation of coal. In this process, coal is heated strongly in the absence of air, which produces coal tar along with other products.

Uses of coal tar:

(i) It is used for making dyes and drugs.

(ii) It is used for making naphthalene balls and roads.

Question: Explain how coal gas is obtained from coal.

Answer: Coal gas is obtained during the process of destructive distillation of coal. In this process, coal is heated strongly in the absence of air. As a result, different products are formed such as coke, coal tar and coal gas. The gas released during this process is called coal gas, which is used as a fuel mainly in industries.

Question: Write the difference between Inexhaustible Natural Resources and Exhaustible Natural Resources.

Answer: The difference between Inexhaustible Natural Resources and Exhaustible Natural Resources is :

Inexhaustible Natural Resources	Exhaustible Natural Resources
These resources are present in unlimited quantity.	These resources are present in limited quantity.
They are not likely to be exhausted by human activities.	They can be exhausted by continuous use.
They are naturally replenished continuously.	They take millions of years to form and cannot be replaced quickly.
Examples: Sunlight, air, wind.	Examples: Coal, petroleum, natural gas.

Question: Describe the different products obtained from petroleum and their uses.

Answer: Petroleum is refined in a refinery by a process called fractional distillation. During this process, different useful products are obtained.

Some important products of petroleum and their uses are:

(i) Petroleum gas (LPG): Used as a fuel for cooking at home and in industries.

(ii) Petrol: Used as a fuel in cars, scooters and motorcycles. It is also used as a solvent for dry cleaning.

(iii) Kerosene: Used as a fuel in stoves and lamps, especially in rural areas. It is also used as aviation fuel.

(iv) Diesel: Used as a fuel in buses, trucks, tractors and generators.

(v) Lubricating oil: Used for lubricating machine parts to reduce friction.

(vi) Paraffin wax: Used in making candles, ointments and cosmetics.

(vii) Bitumen: Used for making roads and in roofing.

Exercises            

1. What are the advantages of using CNG and LPG as fuels?

Answer: The advantages of using CNG (Compressed Natural Gas) and LPG (Liquefied Petroleum Gas) as fuels are:

(i) They can be burnt directly, so they are easy to use in homes and vehicles.

(ii) They can be transported easily through pipelines, which makes their supply convenient.

(iii) They are clean fuels and do not produce smoke when burnt, so they cause less air pollution.

(iv) They produce a large amount of heat energy on burning, so they are efficient fuels.

2. Name the petroleum product used for surfacing of roads.

Answer: The petroleum product used for surfacing of roads is bitumen.

Nowadays, bitumen, which is obtained from petroleum, is used in place of coal-tar for metalling and surfacing of roads. It helps to make the road surface smooth and strong.
3. Describe how coal is formed from dead vegetation. What is this process called?

Answer:  About 300 million years ago, dense forests in wetland areas got buried under soil due to natural processes like flooding. As more layers of soil covered them, heat and pressure increased. Over a long time, the dead plants slowly changed into coal. This slow conversion of dead vegetation into coal is called carbonisation.

4. Fill in the blanks.
(a) Fossil fuels are ………… ,……….. and …………..
(b) Process of separation of different constituents from petroleum is called …………….. .
(c) Least polluting fuel for vehicle is……………….. .

Answer: (a) Fossil fuels are coal, petroleum and natural gas.

(b) Process of separation of different constituents from petroleum is called refining.

(c) Least polluting fuel for vehicle is CNG (Compressed Natural Gas).
5. Tick True/False against the following statements.
(a) Fossil fuels can be made in the laboratory. (T/F)
(b) CNG is more polluting fuel than petrol. (T/F)
(c) Coke is almost pure form of carbon. (T/F)
(d) Coal tar is a mixture of various substances. (T/F)
(e) Kerosene is not a fossil fuel. (T/F)

Answer: (a) Fossil fuels can be made in the laboratory. — False

(b) CNG is more polluting fuel than petrol. — False

(c) Coke is almost pure form of carbon. — True

(d) Coal tar is a mixture of various substances. — True

(e) Kerosene is not a fossil fuel. — False
6. Explain why fossil fuels are exhaustible natural resources.

Answer: Fossil fuels are exhaustible natural resources because their supply is limited in nature and they take millions of years to form from dead plants and animals. However, humans are using them very fast for fuel and energy. Once they are used up, they cannot be replaced quickly, so they may get exhausted.

7. Describe characteristics and uses of coke.

Answer:  Characteristics of coke:
Coke is a tough, porous and black substance. It is an almost pure form of carbon.

Uses of coke:
Coke is used in the manufacture of steel and in the extraction of many metals.
8. Explain the process of formation of petroleum.

Answer: Petroleum was formed from the remains of tiny plants and animals that lived in the sea millions of years ago. When they died, their bodies settled at the bottom and were covered with layers of sand and clay. Over a long time, high temperature and pressure converted them into petroleum and natural gas.
9. The following Table shows the total power shortage in India from 1991–1997. Show the data in the form of a graph. Plot shortage percentage for the years on the Y-axis and the year on the X-axis .

S. No.	Year	Shortage (%)
1.         2.         3.         4.         5.         6.         7.	1991                1992                1993                1994                1995                1996                1997	7.9              7.8              8.3              7.4              7.1              9.2             11.5

Answer: