NCERT Class 8 Science Chapter 5 - Coal and Petroleum

Chapter 5 - Coal and Petroleum

Question 1: What are the advantages of using CNG and LPG as fuels?
Answer: The great advantage of CNG is that it can be used directly for burning in homes and factories where it can be supplied through pipes. 

Question 2: Name the petroleum product used for surfacing of roads.
Answer: Bitumen is the petroleum product which is used for surfacing of roads.

Question 3: Describe how coal is formed from dead vegetation. What is this process called?
Answer: Million 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. As more soil deposited over them, they were compressed. The temperature also rose as they sank deeper and deeper. Under high pressure and high temperature, dead plants got slowly converted to coal. As coal contains mainly carbon, the slow process of conversion of dead vegetation into coal is called carbonisation. Since it was formed from the remains of vegetation, coal is also called a fossil fuel. When it is heated in air, coal burns and produces mainly carbon dioxide gas. Coal is processed in industry to get some useful products such as coke, coal tar and coal gas.

Question 4: Fill in the blanks.
a) Fossil fuels are ______________________, __________________________ and ___________________________.
b) Process of separation of different constituents from petroleum is called ________________________.
c) Least polluting fuel for vehicle is __________________________.
Answer:
a) Fossil fuels are Coal, Petroleum and Natural Gas.
b) Process of separation of different constituents from petroleum is called refining.
c) Least polluting fuel for vehicle is Compressed Natural Gas (CNG).

Question 5: Tick True/False against the following statements.
a) Fossil fuels can be made in the laboratory. (T/F)
b) CNG is more polluting fuel than petrol. (T/F)
c) Coke is almost pure form of carbon. (T/F)
d) Coal tar is a mixture of various substances. (T/F)
e) Kerosene is not a fossil fuel. (T/F)
Answer:
a) False
b) False
c) True
d) True
e) False

Question 6: Explain why fossil fuels are exhaustible natural resources.
Answer: Fossil fuels take millions of years to be formed. The amount of these resources in nature is limited. They can be exhausted by human activities. Once it is exhausted it takes millions of years to form. Therefore, fossil fuels are known as exhaustible natural resources.

Question 7: Describe characteristics and uses of coke.
Answer: Coke is a tough, porous and black substance. It is an almost pure form of carbon. Coke is used in the manufacture of steel and in the extraction of many metals.

Question 8: Explain the process of formation of petroleum.
Answer: 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 transformed the dead organisms into petroleum and natural gas.

Question 9: The following Table shows the total power shortage in India from 1991-1997. Show the data in the form of a graph. Plot shortage percentage for the years on the Y-axis and the year on the X-axis.

Answer: