Coal and Petroleum
Science Class Eight
NCERT Exercise Solution
Question (1) What are the advantages of using CNG and LPG as fuels?
Answer Advantages of using CNG and LPG as fuels
(a) CNG and PNG create much less pollution while burning.
(b) As being in the gaseous form CNG and PNG can be transported through pipe lines and compressed in cylinder easily.
(c) CNG and PNG are cheaper than other fossil fuels.
Question (2) Name the petroleum product used for surfacing of roads.
Answer Coal tar and bitumen, which are petroleum products, used for surfacing of roads.
Question (3) Describe how coal is formed from dead vegetation. What is this process called?
Answer Dense forest situated in low lying wetland areas of earth were buried under the soil due to many natural processes like flooding, earthquake, etc. about 300 million years ago. In the due course more soil were deposited over them again and again and they were compressed. As they went deeper more temperature and pressure act over them. Under such conditions of high temperature and pressure, those dead plants got slowly converted into coal. Since coal was formed from the remains of vegetation, coal is also called a fossil fuel.
The slow process of conversion of dead vegetation into coal is called carbonization as coal contains mainly carbon.
Question (4) Fill in the blanks.
(a) Fossil fuels are ______, ______ and _______.
Answer Fossil fuels are coal, petrol, diesel and natural gas.
(b) Process of separation of different constituents from petroleum is called _________.
Answerrefining of petroleum.
(c) Least polluting fuel for vehicle is ________.
Answer 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)
Answer False (F)
Correct Answer Fossil fuels are natural resources and cannot be made in the laboratory.
(b) CNG is more polluting fuel than petrol. (T/F)
Answer False (F)
Correct Answer CNG is less polluting fuel than petrol.
(c) Coke is almost pure form of carbon. (T/F)
Answer True (T)
(d) Coal tar is a mixture of various substances. (T/F)
Answer True (T)
(e) Kerosene is not a fossil fuel. (T/F)
Answer False (F)
Correct Answer Kerosene is a fossil fuel as it is obtained from petroleum.
Question (6) Explain why fossil fuels are exhaustible natural resources.
Answer
Petroleum, natural gas and coal are fossil fuels. Coal was formed from the remains of vegetation and petroleum was form from the dead remains of organisms. Fossil fuels take millions of years to form. They can be exhausted by human activities. And amount of these fossil fuels are limited. On the other hand these fossil fuels take millions of year to form.
Thus, these fossil fuels are exhaustible natural resources.
Question (7) Describe characteristics and uses of coke.
Answer Characteristics of coke:
(a) Coke is a tough, porous and black substance.
(b) Coke is almost pure form of carbon.
Use of coke
(a) Coke is used in the manufacturing of steel.
(b) Coke is used in the extraction of many metals.
Question (8) 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 Y-axis and the year on the X-axis.
| S.No. | Year | Shortage (%) |
|---|---|---|
| 1 | 1991 | 7.9 |
| 2 | 1992 | 7.8 |
| 3 | 1993 | 8.9 |
| 4 | 1994 | 7.4 |
| 5 | 1995 | 7.1 |
| 6 | 1996 | 9.2 |
| 7 | 1997 | 11.5 |
Answer
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