Chapter 6 | Sources Of Energy | Class- 8 DAV Science Solutions

Are you looking for DAV Books Solutions then you are in right place, we have discussed the solution of Science class 8 book Chapter 5 Sources of Energy which is followed in all DAV School. Solutions are given below with proper Explanation please bookmark our website for further updates!! All the Best !!

DAV Class- 8 Science Sources of Energy Question and Answer

Something To Know

A. Fill in the blanks.

1. Coal and petroleum are non-renewable sources of energy.

2.Wood is a major renewable, natural resource.

3. The process, in which coal is strongly heated in the absence of air, is known as destructive distillation.

4. In oil wells, Natural gas is always found above the layer of petroleum.

5. Coal tar is a black viscous liquid, obtained by destructive distillation of coal.

B. State True or False for the following statements.

1. Fossil fuels are renewable natural resources.	Answer: False
2. Anthracite has higher carbon content than lignite.	Answer: True
3. Coke can be used to make fuel gases.	Answer: True
4. Natural gas is found below the petroleum layers.	Answer: False
5. Burning of fossil fuels is a major source of pollution.	Answer: 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: Substances which produce heat on burning in air are called fuels.

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 plant materials 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: Two uses of asphalt are:

It is used for roads construction.
It is also used for coating the underside of electric poles to prevent their rusting.

(b) paraffin wax

Answer: Two uses of paraffin wax are:

It is used as grease.
It is also used for making vaseline, ointments and candles.

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: Coal was formed from plant remains got buried deep under the earth’s crust. Over a large period of time, the chemical and physical properties of these plant remain were changed through geological action that leads to the creation of the solid material i.e., Coal.

2. Differentiate between lignite and bituminous coal.

Answer: Differentiate between lignite and bituminous coal are:

Lignite Coal	Bituminous Coal
1. It has carbon content of about 38 per cent.	1. It has carbon content about 65 per cent.
2. It has been mainly used for electric power generation.	2. It is used for making coke (other type of fuel) and also for power generation.
3. It produces low heat energy.	3. It produces more heat energy.
4. It has high moisture content.	4. It has low moisture content.
5. It is regarded as the lowest grade of coal.	5. It is regarded as the middle grade coal.

3. How do petroleum and natural gas occur in nature?

Answer: Petroleum is found at moderate depths (500m – 2000m) between two layers of impervious rocks. Petroleum deposits are usually found mixed with salt water. Petroleum being lighter than salt water, floats over it. Natural gas is found above petroleum; it is trapped between the rock cap and the petroleum layer.

4. State the main advantages of using natural gas.

Answer: The main advantages of using natural gas are:

It burns readily and has a high calorific value.
It is easy to carry and store.
It undergoes complete combustion and can be controlled easily.
It is a cleaner fuel as it releases relatively low amounts of gaseous pollutants.
Do not leave ash particles after burning.

5. Keeping in mind their availability in nature, explain the need of using coal and petroleum judiciously.

Answer: Coal and petroleum are finite resources that take millions of years to create. They are non-renewable, in other words. As a result, these fossil fuels should be used wisely so that future generations will have access to them for valuable products.

Value Based Question

Do it yourself

Chapter 6 | Sources of Energy | Class- 8 DAV Science Solutions