Maharashtra BoardEnglish MediumSTD 7ScienceNatural Resources5 Marks
Question
What is meant by fossil fuel? What are their types?
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Answer
Fossil fuels (such as coal or natural gas) are formed in the earth from dead plants and animals, due to high pressure from above and the heat from the earth’s interior.
The dead plants, animals get transformed into fossil fuel.
There are three types of fossil fuels which can be used for energy production, Coal, oil and natural gas.
a. Coal:
Coal is a solid fossil fuel formed over millions of years by the decay of land vegetation,
Coal is a store house of carbon. Coal is found in mines,
It is like porous, hard, black rock.
It is burnt to obtain heat energy.
It is used as a fuel in thermal power plants and to run boilers and railway engines, for cooking and baking bricks.
Anthracite is the coal of the highest grade.
Producer gas and water gas are obtained from coal.
b. Mineral oil:
Mineral oil is the liquid fuel formed by the decomposition of organic substances buried underground,
The underground mineral oil is extracted through oil wells.
Mineral oil is found mainly in oil sands, shale, sandstone and limestone at a depth of about 1000 to 3000 metres.
Mineral oil is also known as petroleum or crude oil. It is greenish-brown in colour.
Petroleum is a mixture of many compounds mainly of the hydrocarbon type.
It also contains compounds of oxygen, nitrogen and sulphur.
Petroleum is extracted through oil wells and refined by fractional distillation to separate other components,
Aviation petrol, gasoline, diesel, kerosene, naphtha, lubricating oil, tar are all obtained from petroleum.
They are used as fuel and for production of dyes, pesticides, perfumes and artificial fibres.
c. Natural gas:
Natural gas is an important fossil fuel.
It is lighter than air. It is found with petroleum in underground oil wells and in some places as natural gas alone.
The main component of natural gas is methane $\left( CH _4\right)$, ethane $\left( C _2 H _6\right)$, propane $\left( C _3 H _8\right)$ and butane $\left( C _4 H _{10}\right)$ are present in small proportions.
This gas is highly flammable.
This fuel can be carried over long distance by means of a gas pipeline.
In absence of pipeline, it is transformed under high pressure into compressed natural gas (CNG) and liquefied natural gas (LNG).
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