Class 8 chapter 5 coal and petroleum

Anything in the environment 'which can be used' is called a resource.

All the natural resource are classified into two main groups:

Inexhaustible natural resources(Renewable resources): Natural resources which are present in unlimited quantity in nature and do not get exhausted by the human activities. For example sunlight, air and water.

Exhaustible natural resources(Non-renewable resources) : Those resources which are present in limited quantity in nature and can be exhausted by human activities. For example: Coal, Petroleum, natural gas, minerals, forest and wildlife.

Fossils: Fossils are the remains of dead plants and animals buried under the earth millions of years ago.

Fossil fuels: The fuel which are formed from the remains of living organisms buried under the earth long long ago are called the fossil fuels. For example Coal, Petroleum and Natural gas.

Coal: Coal is a hard black combustible mineral that consists mainly of carbon it is found deep under the surface of the earth.

Formation of coal: About 300 million ago, there are dense forest in low lying wetland areas. Due to the natural processes like earthquake, volcanoes and flood these forests were buried under the surface of the earth. As more soil deposited over them they were compressed due to the high pressure and high temperature inside the earth and in the absence of air the wood of the buried forest plants and trees slowly converted into coal.

Carbonisation: The slow process by which the dead plants buried deep under the earth have become coal is called carbonisation.

Coal consists mainly of carbon( oxygen,hydrogen and sulphur in very small quantity) when heated in air it burns and produces mainly carbon dioxide and heat.

C + O2 ------> CO2

Coalification: It involves the removal of water and carbon dioxide, a reduction in oxygen and hydrogen contents, an increase in carbon content.

Variety of coal:

1. Anthracite: 96% carbon. Best variety of coal Because it has high heating value and highest carbon content it gives out more heat and produce less dust.

2. Bituminous coal: 65% carbon. It is the most abundant kind of coal it has high heating value and high sulphur content. It is burnt to generate electricity.

3. Lignite : 38% carbon. Considered as a lowest rank coal because it has lowest heating value and lowest carbon content. It is used to generate electricity, synthetic natural gas producing fertilizer product.

Destructive Distillation of coal: The strong heating of coal in the absence of air is called destructive distillation of coal.

https://www.youtube.com/watch?v=ACZXGEOVsWg

Products obtained during destructive distillation of coal:

Coke: a) The residue left behind when destructive distillation of coal is carried out is coke.

b) It is almost pure form of carbon burns with no smoke.

c) It is also used to reduce the metal oxides such as iron and zinc oxide to get metals.

Coal gas:a) It is the mixture of hydrogen, Methane and carbon monoxide and other gases.

b) It was earlier used for domestic cooking and lightning purpose.

Coal Tar: a) It is the thick viscous liquid mainly used for the road construction.

Ammonium compounds: a) Ammonium compounds when dissolved in water give ammoniacal liquor.

b) It is used for making nitrogenous fertilizers.

PETROLEUM

* Petra (rock) + oleum (oil)

* It is a dark coloured, thick crude oil found trapped in underground rocks.

* It is a mixture of several hydrocarbons (compound having only hydrogen and carbon bond), with the no. of carbon atoms varying from one to more than one hundred.

How petroleum was formed

Petroleum was formed by the decomposition of the remains of tiny plants and animals buried under the sea millions of years ago. Their dead bodies sank to the bottom of the sea and covered with mud and sand. Due to high pressure, heat and action of bacteria in the absence of air the dead remains of tiny plants and animals was slowly converted into Petroleum.

Occurrence of Petroleum

* Petroleum occurs deep under the surface of earth between two layers of impervious rock

(rocks which will not permit oil, water or gas to flow through it).

* Natural gas occur above the petroleum oil trapped under the rocks.

Extraction of Petroleum and Natural gas.

* Petroleum is extracted by drilling holes called oil wells in the earth crust.

* Oil Wells are drilled by using drilling rigs. When an oil well is drilled through rock, natural gas comes out first with great pressure, after sometime crude petroleum oil comes out by itself due to the gas pressure.

*After the gas pressure reduced, petroleum is pumped out of the oil well.

The crude oil (petroleum) pump out from a well is a black liquid because of its importance it is referred to as a black gold.

Refining of Petroleum

The Crude petroleum oil is a complex mixture of many hydrocarbons.

Fractions: Components with different boiling points.

Refining: The process of separating the crude petroleum oil into more useful fractions called refining.

The various hydrocarbons present in petroleum have different boiling points. As the carbon atoms in hydrocarbon increases its boiling point also increases and this property is used to separate the different components of Petroleum.

Fractional distillation: The separation of Petroleum into different fractions is done by the process of fractional distillation.

Process involved in refining:

* Crude oil is first heated at about 400 degree centigrade in a furnace.

* The vapour formed are passed into a tall fractionating column.

* The hydrocarbon with the highest boiling point condense first at the base of the fractionating tower.

* As the vapour rises hydrocarbon with different boiling point condense at a different heights.

* The hydrocarbon with only 1 to 4 carbon atoms which exist in the gaseous state do not condense and escape from the top of the tower as a petroleum gas.

The various fractions of Petroleum:

1. Fraction: Petroleum gas:

Boiling point below 40 degree Celsius.

Number of carbon atoms (1-4)

Product obtained: Liquefied Petroleum Gas (LPG) used as fuel for the home and industry.

2. Fraction: Gasoline and Naphtha

Boiling point 90 - 165 degree Celsius

Number of carbon atoms (4- 10)

Product obtained: Petrol used as a motor fuel, aviation fuel & solvent for the dry cleaning.

3. Fraction: kerosene

Boiling point 150 - 245 degree Celsius

Number of carbon atoms (10-16)

Product obtained: kerosene used as a domestic fuel( pressure stoves to cook food and in lanterns for lightening purposes) and jet engine fuel.

4. Fraction: Light oil

Boiling point 215 - 315 degree Celsius

Number of carbon atoms (16 - 20)

Product obtained: Diesel used as a fuel for the motor vehicles and electric generator.

5. Fraction: Residue

Boiling point over 370 degree Celsius

Number of carbon atoms over 25

Product obtained: Lubricating oil used to lubricate the machine

Paraffin wax used in making candles, vaseline, ointments etc.

Asphalt (Bitumen) used in making black paints and for roads surfacing.