8th Class Science Coal and Petroleum

Coal and Petroleum

Synopsis

• Sources of energy:

All sources of energy can be divided into two categories:

(i) renewable sources of energy and

(ii) non - renewable sources of energy.

• Renewable sources of energy: The sources of energy which are found in nature and inexhaustible are called renewable sources of energy. Some renewable sources of energy are solar energy, geothermal energy, wind energy, tidal energy, bio-energy.

• Non-renewable sources of energy: The sources of energy which have accumulated in nature over a long period of time and cannot be quickly replaced once exhausted are called non-renewable sources of energy. Some non-renewable sources of energy are fossil fuels like coal, petroleum, natural gas.

• Coal and its products: Coal is a complex mixture of elements like carbon, hydrogen and oxygen. Coal is formed by the process of carbonisation. Coal is one of the cheapest and widely used fuels. Anthracite, bituminous, lignite and peat are different varieties of coal. The most important variety of coal which is used as a fuel is bituminous coal. The process of heating coal in the absence of air is called destructive distillation. Destructive distillation of coal gives products like coal gas, ammonical liquor, coal tar and coke.

• Coke obtained from coal is used to make fuel gases like water gas and producer gas.

• Coal tar is a black, thick liquid with an unpleasant smell.

• Coal gas is a mixture of hydrogen, methane and carbon monoxide.

• Petroleum and its products: Economy of a nation depends, to a great extent, on its petroleum wealth. That is why petroleum is called 'Black Gold'.

• Crude oil is a complex mixture of solid, liquid and gaseous hydrocarbons mixed with water, salt and other particles.

• Petroleum is lighter than water and insoluble in it. Petroleum is a dark coloured, viscous and a strong smelling liquid.

• Petroleum is extracted by drilling holes in the earth's crust, sinking pipes and pumping out the oil. Petroleum is then refined by fractional distillation. Important fractions of petroleum are gasoline, kerosene, diesel, lubricating oil, petrol, etc.

• Coal and petroleum resources are limited, so we should use them judiciously.

Natural gas: Natural gas is stored under high pressure as CNG which is used for power generation and fuel. It is a cleaner fuel and less polluting. It consists mainly of methane (85%), ethane (10%), propane (3%) and others.