Class 8 Science Chapter 3 Question Answers - Coal And Petroleum

Q1: Discuss importance of natural gas in our daily life.

Ans: Natural gas is very important fossil fuel as it is very easy to transport through pipes, apart from this also it can be stored under high pressure as compressed natural gas (CNG) which is being used now a day as a fuel for transport vehicle.
CNG stands for Compressed Natural gas. In CNG compressed gas (which is mainly methane gas) is stored under high pressure as compressed natural Gas.
Advantages of CNG:

• CNG is a very important fossil fuel because it is easy to transport through pipes.
• CNG is also used for power generation and now used as fuel for transport vehicles because it is less polluting.
• It is a cleaner fuel.
• CNG-powered vehicles have lower maintenance costs when compared with other fossil fuel-powered vehicles.
• CNG fuel systems are sealed, which prevents any spill or evaporation losses.
• Natural gas is also used as starting material for the manufacture of a number of chemicals and fertilisers.

Q2: Explain fossil fuels. 

Ans: Some exhaustible natural resources like coal, petroleum and natural gas are called fossil fuels as they are formed from the dead remains of living organisms (fossils). Fossil fuels are non-renewable resources because they take millions of years to form, and reserves are being depleted much faster than new ones are being made. The production and use of fossil fuels raise environmental concerns.
Coal: About 300 years ago the earth had dense forests in low lying wetland areas. Due to natural processes, like flooding these forests got buried under the soil. They get sank deeper and deeper and temperature gets increasing day by day, under high pressure and high temperature dead plants slowly got converted to coal. Coal's primary use is for the generation of electricity. It is also used in the industrial and retail sector as fuel for heating and powering foundries, cement plants and other industrial and manufacturing facilities.
Petroleum: 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 in absence of air and under high temperature and high pressure the dead organisms get transformed into Petroleum and natural Gas. Petroleum is a dark oily liquid. It has an unpleasant odour. It is a mixture of various constituents such as Petrol, Diesel, etc. and the process of separating these constituents from crude oil is called Refining.
Q3: Describe coal and its various products along with their uses.

Ans: Coal is a hard and black coloured non-metal which is used to cook food, in the past it was also used to run railway engines, apart from this it is also used to produce electricity in thermal power plant; it is also used as fuel in various industries.
Following are the products of coal:
1. Coke: Coke is a product of coal; it is tough, porous, and black in colour and almost pure formof carbon. It is used in making steels and in extraction of many metals
2. Coal tar: coal tar is the product of coal which is the mixture of various substances. Products obtained from coal tar is used for manufacturing a variety of products like dyes, drugs, perfumes, explosives, paints, photographic materials, roofing materials etc.
3. Coal gas: Coal gas is obtained during the processing of Coal to get coke. It is used as a fuel in many industries situated near the coal processing plants.

Q4: Write notes on wide and judicious use of our exhaustible natural resource.

Ans: Exhaustible resources like coal, petroleum are formed from the dead organisms, it takes millions of years for formation of these fuels, and On the other hand the known reserves of these will last almost a few hundred years. A part from this since these products are not environmental friendly as burning of these fuels is a major cause of air pollution and their use is also linked to global warming therefore we should use these resources only when it is actually required. Wise use of natural resource will result in better environment, smaller risk of global warming and their availability for a longer period of time.
 Q5: 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.

Q6: 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.