Page 61 - Science Class 08

Liquid : Some liquid fuels are kerosene oil, organic ma er present. How long it was buried,
petrol, diesel, alcohol, liquefied, hydrogen, etc. and what temperature and pressure condi ons

Gaseous : Some gaseous fuels are natural gas, existed when they were decomposing?
liquefied petroleum gas (LPG), petrol gas, gobar There are three major types of fossil fuels:
gas, coal gas, water gas (H + O), acetylene,
2 v Coal is formed from ferns, plants and trees
hydrogen gas, etc. which hardened due to pressure and heat

Occurrence v Oil is formed from smaller organisms, like
On the basis of the occurrence of the fuels, we zooplankton and algae. Intense amount of
can grouped them into natural fuels and pressure caused this complex organic
processed fuels. ma er to decompose into oil.

Natural Fuels : Fuels which are used in the v Natural gas undergoes the same process as
form in which they occur in nature are called oil; however the process is longer and
natural fuels or primary fuels. subject to higher amounts of heat and

For example, wood, coal, natural gas, petroleum, pressure, causing further decomposi on.
ca le dung, bagasse, agricultural wastes
obtained from crops, etc.
Processed Fuels : Some natural fuels are used

a er a long physical and chemical process.
These fuels are, therefore, called the processed
fuels or secondary fuels.
For example, charcoal, coke, petrol, diesel, Coal Oil
kerosene, water gas, coal gas, etc. PETROLEUM

Fossil Fuels Petroleum crude oil is a mixture of hydro-
Fossil fuel is a term used to describe a group of carbons formed originally from marine animals
energy sources that were formed from ancient and plants, found beneath the ground trapped
plants and organisms during the Carboniferous between layers of rocks. That is why, it is called
Period, approximately 360 to 286 million years the earth’s petroleum (petra means rock and
ago, prior to the age of dinosaurs. oleum mean oil). Petroleum is obtained in its

At that me, the land was covered with raw form. We obtain petrol and other products
swamps filled with microorganisms, marine of petroleum like diesel and kerosene a er
organisms, trees, ferns and other large leafy refining petroleum.
plants. As the organisms and plants died, they
sank to the bo om of the swamps and oceans
and formed layers of a spongy material called
peat. Over millions of years, the peat was
covered by sand, clay and other minerals,
which converted the peat into sedimentary

rock. Over me, different types of fossil fuels
formed, depending on the combina on of
Petroleum
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