Long Answers - Coal and Petroleum, Science, Class 8 PDF Download

LONG ANSWER TYPE QUESTIONS 
 

Q. 1. Describe the process of formation of coal in the nature.
Ans. About 300 million years ago, the earth had dense forests in low-lying wetland areas. Due to natural processes like flood, earthquakes and volcanic eruptions, 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 temperature and pressure buried plants got slowly converted to coal. The coal contains mainly carbon. The slow process of conversion of dead vegetation into coal is called carbonisation. It was formed from the remains of vegetation. Coal is called fossil fuel.

 Q. 2. Describe the process of formation of petroleum.  
Ans. Petroleum is a dark oily liquid. It is a mixture of various fractions. 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 and action of microorganisms, transformed the dead organisms into petroleum and natural gases. The layer containing petroleum and natural gas is above that of water. Oil and gas are lighter than water and do not mix with it.

Q. 3. Write the names of various components of petroleum and write their uses.
Ans. The petroleum is the mixture of various fractions. These fractions are separated by the process of refining: We get following fractions by the process of refining:

(1) LPG (Liquefied Petroleum Gas):  

Uses:  It is used as domestic and industrial fuel.

(2) Petrol  

Uses:  It is used as motor fuel, aviation fuel and solvent for drycleaning.

(3) Kerosene  

Uses:  It is used as fuel for stoves, lamps and for jet aircraft.

(4) Diesel  

Uses:  It is used as fuel for heavy motor vehicles and electric generators.

(5) Lubricating  Oil  

Uses:  It is used as a lubricant.

(6) Paraffin  Wax  

Uses:  It is used in making ointments, candles and vaseline etc.

(7) Bitumen  

Uses:  It is used in making paints and road surfacing.
 

Q. 4. What advise is given by PCRA for saving petrol and diesel?
Ans. The advise given by PCRA are as following:
(i) Drive at a constant and moderate speed as far as possible.
(ii) Switch off the engine at traffic lights or at a place where you have to wait.
(iii) Ensure correct tyre pressure.
(iv) Ensure regular maintenance of the vehicle. If we follow the tips given by PCRA, then we can save more and more petrol or diesel. In this way we can save money and energy of the nation.