NCERT class 8 is one of the important phase of a student's life, in class 8 many new topics are added. To score good marks in class 8th examinations students should solve the NCERT questions provided at the end of each chapter. Solving the NCERT questions will help you to understand the chapter in a better way. Sometimes NCERT questions are directly asked in the school examinations .
Here we have provided the NCERT solutions for class 8 science chapter 5 PDF for better understanding and clarification.
Compressed Natural Gas (CNG) and Liquefied Petroleum Gas (LPG) are used as fuels. What are its advantages?
The advantages of using CNG and LPG as fuels are as follow:
- CNG and LPG can be transported easily through pipe lines.
- CNG and LPG burn easily.
- CNG and LPG are clean fuels and they do not release smoke when burnt.
- CNG and LPG give a lot of heat energy when burnt.
What is the process called where coal is formed from dead vegetation? Explain how.
Dense forests got buried under the soil due to natural processes, millions of years ago. More and more soil got deposited over them and they got compressed more. This led them to get exposed to very high temperature and pressure. They slowly got converted into coal under these extreme conditions. The whole process of formation of coal from dead vegetation is known as carbonization.
For the surfacing of roads, which petroleum product do you think is used?
Bitumen is used for the surfacing of roads.
Fill in the blanks.
a) Process of separation of different constituents from petroleum is called__________.
b) Fossil fuels are ___________, ___________ and __________.
c) The least polluting fuel for vehicles is __________.
b) coal, petroleum and natural gas.
c) compressed natural gas (CNG).
Mark ‘T’ if the statement is true and ‘F’ if it is false for the following statements.
a) Fossil fuels can be made in the laboratory. ( )
b) Coke is an almost pure form of carbon. ( )
c) CNG is a more polluting fuel than petrol. ( )
d) Kerosene is not a fossil fuel. ( )
e) Coal tar is a mixture of various substances. ( )
Fossil fuels are exhaustible natural resources. Explain.
The process of formation of fossil fuels requires millions of years. Dead vegetation and animals that get buried deep inside the earth require high temperature and pressure for the formation of fossil fuels, which cannot be done in the laboratory. Thus, fossils are limited. Therefore, the use of fossil fuels at this rate will lead to their exhaustion.
Write the characteristics and uses of coke.
i) Coke is tough.
ii) Coke is porous.
iii) Coke is black in colour.
i) In the manufacture of steel.
ii) In the extraction of metals (as a reducing agent).
Explain the process of formation of petroleum.
Dead organisms that got buried in the sea millions of years ago got covered with layers of sand and clay. Due to lack of air, high temperature, and high pressure, these dead organisms got transformed into petroleum and natural gas.
The below given table shows the total power shortage in India from1993 – 1999. Show the given data in the form of agraph. The x-axis represents the year and Y-axis represents the shortage percentage for the years. Plot the graph.