DAV Solutions Class 8 Science Chapter 6
DAV Solutions for Class 8 Science Chapter 6 Sources of Energy of The Living World Book is prepared for the benefit of DAV Class 8 students. They cover the DAV Syllabus (2021-22) and comprise answers to the questions in the Class 8 Science Chapter 6. This solution guides you in your exam preparation and to understand the topic thoroughly. To score good marks in the school examinations, students should solve the DAV questions Class 8 Science provided at the end of each chapter. Class 8 is one of the important phases of a student’s life. Students learn many new topics in Class 8, which are the basis for the topics included in higher classes.
These DAV Solutions for Class 8 Science Chapter 6 has answers to the questions on coal, natural gas and petroleum and other fossil fuels, the formation of fossil fuels, uses of fossil fuels, types of fossil fuels, and limitations of using fossil fuels. These DAV Solutions are prepared systematically by experienced teachers which will not only help you in your exam preparation but also help you in understanding the topic in-depth.
DAV Class 8 Science Chapter 6 Question Answer
DAV Solutions for Class 8 Science Chapter 6 Sources of Energy is given below. Here DAV Class 8 Science Chapter 6 Question Answer is provided with great explanation. Here we will solve fill in the blanks, true or false, tick the correct option, answer the following questions in brief and answer the following questions or long answer question.
- Fill in the blanks.
- True or False.
- Tick the correct option.
- Answer the following questions in brief.
- Answer the following questions.
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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
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 (2) True (3) True (4) False (5) True
1. The highest grade of coal is known as-
2. Coke and coal tar are obtained from-
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
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:
Answer: Two uses of asphalt are:
- It is used for making roads.
- 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.
CNG – Compressed Natural Gas.
LPG – Liquified Petroleum Gas.
PNG – Piped Natural Gas.
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 limited and take millions of years for their formation. i.e., they are non-renewable. Hence these fossil fuels should be used judiciously so that they will be available to future generations for useful products.