DAV Class 8 Science Solution Chapter 6 Sources of Energy
DAV School Books Class 8 Science Solution Chapter 6 Sources of Energy all Question Answer. DAV Class 8 6th Chapter Sources of Energy full Chapter explanation by expert teacher.
DAV School Books Class 8 Science Solution Chapter 6 Sources of Energy
A.) Fill in the blanks.
1.) ___________ and ___________ are non-renewable sources of energy.
2.) ___________ is a major renewable, natural resource.
3.) The process, in which coal is strongly heated in the absence of air, is known as ___________.
4.) In oil wells, ___________ is always found above the layer of petroleum.
5.) ___________ is a black viscous liquid, obtained by destructive distillation of coal.
Answer: (1) Coal, petroleum (2) Wood (3) destructive distillation (4) natural gas (5) Coal tar
B.) State True or False for the following statements.
1.) Fossil fuels are renewable natural resources.
2.) Anthracite has higher carbon content than lignite.
3.) Coke can be used to make fuel gases.
4.) Natural gas is found below the petroleum layers.
5.) Burning of fossil fuels is a major source of pollution.
Answer: (1) False , these are non-renewable natural resources.(2) True (3) True (4) False , it is found above thee petroleum layers(5) True
C.) Tick the correct option.
1.) The highest grade of coal is known as-
Answer: anthracite
2.) Coke and coal tar are obtained from-
Answer: coal
3.) Different types of coal generally have the-
Answer: different content of volatile material as well as different percentage of carbon.
4.) A product, that is not obtained through the refining of petroleum, is-
Answer: coal gas
5.) Which of the following is a renewable source of energy?
Answer: tidal energy
D.) Answer the following questions in brief.
1.) Define the term ‘fuel’.
Answer: Any Substances that produces heat on burning in air are called fuels, fuels are mostly a natural resource.
2.) Name any two renewable natural sources of energy.
Answer: Wind energy and water energy.
3.) Define the term ‘carbonisation’.
Answer: The process of conversion of dead remains of a plant upon decomposition into coal, is called carbonisation.
4.) Name the three main products obtained from destructive distillation of coal.
Answer: Coke, Coal Tar & Coal gas.
5.) State two uses each of the following:
(a) asphalt
Answer: Road construction is one of asphalt’s two uses.
It is also used to coat the underside of electric poles to prevent rusting.
(b) paraffin wax
Answer:There are two uses for paraffin wax: as grease.
Additionally, it is used to create candles, ointments, and vaseline.
.
6.) Write the full forms of CNG, LPG and PNG.
Answer:
CNG – Compressed Natural Gas.
LPG – Liquified Petroleum Gas.
PNG – Piped Natural Gas.
E.) Answer the following questions.
1.) Describe, in brief, the process of ‘coal formation’.
Answer:.
Dead and decaying organic matter such as dead plant and animal remain were first buried within the earth.For thousands of years these material have undergone geological action and their chemical and physical compositions have been changed these have led to the formation of fossil and fuels
2.) Differentiate between lignite and bituminous coal.
Answer: Differentiate between lignite and bituminous coal are:
Lignite Coal |
Bituminous Coal |
1. It has a very high carbon content of approximately 38 per cent. | 1. It has even higher carbon content of about 65 per cent. |
2. It used in power plants to generate electricity | 2. It is used for production of coke |
3. It contains a lot of moisture | 3. It contains less moisture |
4.It is considered as inferior quality amongst coal | 4. It is considered as a better quality amongst coal |
3.) How do petroleum and natural gas occur in nature?
Answer: Petrol is found deep down around 500 to 200 m below the surface of Earth It is typically found trapped between two layers of impervious rock
4.) State the main advantages of using natural gas.
Answer: Natural gas having a high calorific value makes it easier to burn hence it becomes a good fuel.It is cheaper than other fuels it easier to control it as it completely burns it emits lesser gaseous pollutants it does not leave as a by product
5.) Keeping in mind their availability in nature, explain the need of using coal and petroleum judiciously.
Answer: Both petroleum and coal are fossil fuels and hence are nonrenewable natural resources if we keep on using them we will run out of them and it won’t be easy for us or the nature to produce them again as it will take thousands of years to be produced again hence it is necessary that we judiciously use them