KENDRIYA VIDYALAYA SHAHDARA

CLASS VIII

SUBJECT- SCIENCE

CHAPTER -5
COAL AND PETROLEUM

PREPARED BY:
SHASHI BALA
TGT (BIOLOGY)
 INTRODUCTION
We use various materials for our basic needs. Some of them are found in
nature and some have been made by human efforts.
The materials or substances occurring in nature which can be exploited for
basic needs are called Natural Resources.
TYPES OF NATURAL RESOURCES
1. Inexhaustible Natural Resources
2. Exhaustible Natural resources
 Inexhaustible Natural Resources
The resources which are present in unlimited quantity in nature and are
not likely to be exhausted by human activities are called Inexhaustible
Natural Resources.

Examples are: sunlight, air.

 Exhaustible Natural Resources

The resources which are present in limited amount in nature are called
Exhaustible natural resources. They can be exhausted by human
activities.

Examples: forests, wildlife, minerals, coal, petroleum, natural gas etc.

In this chapter we will learn about some exhaustible
natural resources like coal, petroleum and natural
gas. These were formed from the dead remains of
living organisms (fossils). So, these are all known as
fossil fuels.
 COAL
• It is as hard as stone and is black in colour.
• It is used
a) to cook food.
b) in railway engines to produce steam to run the engine.
c) in thermal power plants to produce electricity.
d) as a fuel in various industries.
• When heated in air, coal burns and produces mainly carbon dioxide gas.
• Coal is processed in industry to get some useful products such as coke, coal
tar and coal gas.
 How coal is formed?

• About 300 million years ago the earth had dense forests in low lying wetland
areas. Due to natural processes, like flooding, these forests got buried under
the soil. As more soil deposited over them, they were compressed. The
temperature also rose as they sank deeper and deeper. Under high pressure
and high temperature, dead plants got slowly converted to coal. As coal
contains mainly carbon, the slow process of conversion of dead vegetation
into coal is called carbonisation. Since it was formed from the remains of
vegetation, coal is also called a fossil fuel.
Coke
• It is a tough, porous and black substance. It is an almost pure form of
carbon.
• Coke is used in the manufacture of steel and in the extraction of many
metals.
Coal Tar
• It is a black, thick liquid with an unpleasant smell.
• It is a mixture of about 200 substances.
• Products obtained from coal tar are used as starting materials for
manufacturing various substances used in everyday life and in industry, like
synthetic dyes, drugs, explosives, perfumes, plastics, paints, photographic
materials, roofing materials, etc.
• Naphthalene balls which are used to repel moths and other insects are also
obtained from coal tar.
Coal Gas
• Coal gas is obtained during the processing of coal to get coke. It is used as a
fuel in many industries situated near the coal processing plants.
• Now-a-days it is used as a source of heat rather than light.

NOTE
Bitumen, a petroleum product, is used in place of coal-tar for metaling the
roads now-a days.
 PETROLEUM
• The word petroleum is derived from petra (rock) and oleum (oil) as it is
mined from between the rocks under Earth.
• Petroleum is a dark oily liquid.
• It has an unpleasant odour.
• It is a mixture of various constituents such as petroleum gas, petrol, diesel,
lubricating oil, paraffin wax, etc.
• Petrol and diesel are obtained petroleum.
(Petrol is used as a fuel in light automobiles such as motor cycles/ scooters
and cars. And diesel is used as a fuel for heavy motor vehicles like trucks and
tractors.)
 How petroleum is formed?

• Petroleum was formed from organisms living in the sea. As these organisms
died, their bodies settled at the bottom of the sea and got covered with
layers of sand and clay. Over millions of years, absence of air, high
temperature and high pressure transformed the dead organisms into
petroleum and natural gas.
 Refining of Petroleum
• The process of separating the various constituents/ fractions of petroleum is
known as refining. It is carried out in a petroleum refinery
Many useful substances are obtained from petroleum and
natural gas.
These are termed as ‘Petrochemicals’. These are used in
the manufacture of detergents, fibres (polyester, nylon,
acrylic etc.), polythene and other man-made plastics.
Hydrogen gas obtained from natural gas, is used in the
production of fertilisers (urea). Due to its great commercial
importance, petroleum is also called ‘black
gold’.
 Natural Gas
• Natural gas is a very important fossil fuel because it is easy to transport
through pipes.
• Natural gas is stored under high pressure as compressed natural gas (CNG).
• CNG is used for power generation.
• It is used as a fuel for transport vehicles because it is less polluting.
• It is a cleaner fuel.
• The great advantage of CNG is that it can be used directly for burning in
homes and factories where it can be supplied through pipes.
• Natural gas is also used as a starting material for the manufacture of a
number of chemicals and fertilisers.
• In India, natural gas has been found in Tripura, Rajasthan, Maharashtra and
in the Krishna Godavari delta.
 Some Natural Resources are Limited

Coal and petroleum are fossil fuels. It required the dead organisms
millions of years to get converted into these fuels. On the other
hand, the known reserves of these will last only a few hundred
years. Moreover, burning of these fuels is a major cause of air
pollution. Their use is also linked to global warming. It is therefore
necessary that we use these fuels only when absolutely necessary.
This will result in better environment, smaller risk of global
warming and their availability for a longer period of time.
 How can we save petrol/diesel while driving ?

• Drive at a constant and moderate speed as far as possible.

• Switch off the engine at traffic lights or at a place where you have to wait.
• Ensure correct tyre pressure.
• Ensure regular maintenance of the vehicle.
 WORKSHEET
Q.1 What are the advantages of using CNG and LPG as fuels?
Q.2. Name the petroleum product used for surfacing of roads.
Q.3. Describe how coal is formed from dead vegetation. What is this process called?
Q.4 Make a list of various materials used by us in daily life and classify them as natural and
man-made.

Natural Man- made

Q.5 Can coal, petroleum and natural gas be prepared in the laboratory from dead organisms?
Q.6 What does CNG stands for? Why is it considered to be a better fuel than petrol?
Q.7 While driving what are the tips we must follow to save petrol/diesel/natural gas?
 WORKSHEET
Q.8 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 1991 7.9
2 1992 7.8
3 1993 8.3
4 1994 7.4
5 1995 7.1
6 1996 9.2
7 1997 11.5
THANK YOU….