Case Study Based Questions: Coal and Petroleum | Science Class 8 PDF Download

Case Study

Nowadays we are very much dependent on fossil fuels. Increase in the use of coal and petroleum has led to difficulties in managing fossil fuels, and now the time is not far when we run on shortage of them. There are many steps taken by the different governments to decrease the consumption of fossil fuels such as promoting natural gases and making it mandatory for all the vehicles or promoting the usage of electric vehicles on subsidised costs. Coal and petroleum are very useful sources. We need to save them so that it gets easier to manage our natural resources. There are many alternatives like solar energy, electric vehicles, etc which are environment friendly. Many countries are trying to replace all the vehicles which run on diesel and petrol with electric vehicles by 2030. Some serious steps need to be taken in order to manage these sources and save our environment.

Q1: An ideal fuel should have a _________calorific value.
(a) Low
(b) High
(c) Sufficient
(d) None of the above.
Ans: (b)
Sol: An ideal fuel should have a high calorific value because calorific value of a fuel is the amount of heat liberated on complete burning of a unit mass or volume of a fuel. It is expressed in kJ/kg.

Q2: Which of the following is not a fossil fuel?
(a) Kerosene
(b) Coal tar
(c) Water
(d) Petrol
Ans: (c)
Sol: Water is not a fossil fuel. It is a natural resource which is present in unlimited quantity in nature and will not get replenish.

Q3: Explain how the use of CNG in automobiles has reduced pollution in our cities.
Ans: Compressed Natural Gas (CNG) is a clean fuel and does not give smoke when burnt as compared to other petroleum containing fuels like petrol and diesel.

• For automobiles to run, petroleum fuel is burnt.
• The combustion of fuel leaves unburnt carbon particles in the air, along with carbon monoxide (CO) – poisonous and harmful gas.
• Breathing CO causes headache, dizziness, etc.
• CNG burns completely leaving no harmful residue. Hence, the use of CNG in automobiles has reduced pollution in our cities.

Q4: What are petrochemicals?
Ans: Petrochemicals are chemical products obtained from petroleum and natural gas are used in the manufacture of detergents, fibers (polyester, nylon, acrylic etc.), polythene and other man-made plastics. Hydrogen gas is obtained from natural gas, is used in the production of fertilisers (urea).