Saturday, 27 February 2016

TEXTBOOK ANSWERS AND SOLUTIONS OF CBSE CLASS VIII SCIENCE-Chapter-5 COAL AND PETROLEUM




Exercise


1) What are the advantages of using CNG and LPG as fuels?

ANSWER:-The advantages are'-:-
(i) They can be burnt directly.
(ii) They can be transported easily through pipe lines.
(iii) They are clean fuels and do not give smoke when burnt.
(iv) They give a lot of heat energy when burnt.

2) Name the petroleum product used for surfacing of roads.

ANSWER:-Bitumen, a petroleum product, is used for surfacing roads.

3) Describe how coal is formed from dead vegetation. What is this process 
called?




ANSWER:-A long time back, about 300 million years ago the earth had dense forests in low lying wetland areas. Due to natural processes, like earth quakes, flooding, these forests got buried under the soil, rocks and other land masses. With the passage of time, 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.

4) Fill in the blanks:

(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 --CNG--

5) Tick True/False against the following statements:

(a) Fossil fuels can be made in the laboratory. ( F)
(b) CNG is more polluting fuel than petrol. ( F)
(c) Coke is almost pure form of carbon. ( T )
(d) Coal tar is a mixture of various substances. ( T )
(e) Kerosene is not a fossil fuel. (F)

6) Explain why fossil fuels are exhaustible natural resources.

ANSWER:-Fossil fuels are exhaustible natural resources, as limited fossil fuels reserves like coal, petroleum, natural gas are being depleted very fast by human activities like rapid urbanization, industrialization and transportation.

7) Describe characteristics and uses of coke.

ANSWER:-Characteristics of coke are:
(i) Tough
(ii) Porous
(iii) Black in colour

Uses of coke:
(i) In manufacture of steel.
(ii) In the extraction of metals (as a reducing agent).
Coke is used in the homes for cooking, heating and in industries, for manufacturing of steel and extraction of many metals. Earlier it was also used in steam engines for rail transportation. It is also used in thermal power plants to produce electricity.

8) Explain the process of formation of petroleum.

ANSWER:-Petroleum was formed from dead organisms that got buried in the sea millions of years ago. These dead bodies got covered with layers of sand and clay. Lack of air, high, temperature, and high pressure transformed these dead organisms into petroleum and natural gas.

9) The following Table shows the total power shortage in India from 1991–1997. Shown 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. (REFER TO THE BOOK)

ANSWER:-





Written By Badal Paul
The author is a passionate blogger, writer and educationalist. This blog is created to ease troubles of the Cbse students. The author holds multiple blogs and the writer of the Novel KALCHAKRA, OOM AND THE CHOSEN FIVE.