RBSE Class 8 Science Chapter 18 Carbon and Fuel Solutions

In RBSE Class 8 Science Chapter 18 Carbon and Fuel, students learn about the presence and uses of coal as a fuel in our daily lives and how it is used for combustion and other purposes. In this article, we present you the key questions along with solutions of this chapter that will help students to obtain a solid understanding of all important topics and excel in it easily.

The solutions of this chapter have been designed by our subject-matter experts in a lucid manner along with key explanations of chapter-wise important questions, as per the RBSE Class 8 Science syllabus. We hope these readily available solutions will help students to explore new concepts and strengthen their foundation while prepping up for the RBSE Class 8 2020 exam.

Along with the exercise and textbook questions, we have added a few solved additional questions with solutions of the RBSE Class 8 Science for Chapter 18 Carbon and Fuel from the RBSE Class 8 Science Syllabus. Students can refer to these textbook solutions and practice from these questions to have in-depth knowledge and understanding of the chapter and revise from these solutions before sitting for their exams and score well in this subject.

Rajasthan Board Class 8 Science Chapter 18: BYJU’S Important Questions & Answers

RBSE Class 8 Science Chapter 18 Objective Questions: Textbook Important Questions and Solutions

Multiple Choice Questions (MCQs)

Choose the correct option:

Question 1: The coal in which carbon content is highest?

(a) Peat

(b) Lignite

(c) Anthracite

(d) Bituminous

Answer: (c) Anthracite

Question 2: The residue of fractional distillation of petroleum is

(a) Lubricant oil

(b) Wax

(c) Coal tar

(d) Diesel

Answer: (c) Coal tar

Question 3: The crystalline allotrope of carbon is –

(a) Coal

(b) Kajal

(c) Charcoal

(d) Graphite

Answer: (d) Graphite

Fill in the blanks:

Question 4: ____________________ is the domestic liquid fuel.

Answer: Kerosene

Question 5: In graphite each carbon atom is attached to _____________ nearest carbon atoms while in diamond each carbon atom is attached to ____________ nearest carbon atoms.

Answer: three, four

Question 6: ___________________ is necessary for combustion.

Answer: Oxygen

Put True (T) for correct and False (F) for incorrect for the following:

Question 7: The carbon content in Lignite is 67%.

Answer: T

Question 8: Peat coal is an example of liquid fuel.

Answer: F

Question 9: Lubricant oil is used as fuel in vehicles and kitchens.

Answer: F

Question 10: The crystalline allotropes of carbon are diamond, graphite and fullerene.

Answer: T

Short Type Answer Textbook Questions

Question 1: Write the uses of petroleum gas.

Answer: Petroleum gas is a liquid fuel which is mainly used in automobiles such motor bikes, cars, buses, trucks, etc. It is also used in the kitchen as a fuel for cooking purposes.

Question 2: We should sensibly use petrol and diesel like substances. Explain why.

Answer: We should sensibly use petrol and diesel like substances because of the following reasons:

1. Petrol and diesel cause air pollution.

2. It’s an elaborate process which takes time to form oxide oil or natural fuels.

3. Their deposits are in limited quantity which might last only for another 100 years.

4. They are a major causative factor of global warming.

Question 3: Write differences between diamond and graphite.

Answer: Given below are the differences between diamond and graphite:

Sl. No. Properties Diamond Graphite
1. Soft/hard It is a transparent and hard substance It is a powdered substance which is oily and gliding in nature
2. Structure The carbon atom in it forms a tetrahedral structure by joining with 4 carbon and form a three dimensional structure It forms a hexagonal structure by attaching with three other carbon atoms in one dimension only. Likewise, many layers remain attached to each other through weak bonds, so that one layer slides on another layer. Therefore, they are soft
3. Electrical conductance It is insulator electricity but conductor of heat It is a conductor of electricity
4. Uses It is used in making jewellery, cutting glasses, grinding and making holes It is used in pencils, dry cells and electric arcs

Question 4: Compare L.P.G and Wood as Fuel.

Answer: Given below are the differences between L.P.G and Wood as Fuel:

Sl. No. L.P.G Wood
1. It causes less air pollution. It causes air pollution.
2. It doesn’t produce ash. It produces ash.
3. It produces more heat in less time. It takes more time to produce heat.
4. It burns completely. It doesn’t burn completely.

Question 5: Name five compounds of carbon.

Answer: Given below are the names of five compounds of carbon:

1. Petrol

2. Wood

3. Diesel

4. Coal

5. Kerosene

Long Type Answer Textbook Questions

Question 6: Draw a well labelled diagram of diamond and graphite and explain their difference.

Answer: Here’s a labelled diagram of diamond and graphite:

Structure of Diamond

Structure of Diamond

Structure of Graphite

Structure of Graphite

Differences between Diamond and Graphite

Sl. No. Properties Diamond Graphite
1. Soft/hard It is a transparent and hard substance It is a powdered substance which is oily and gliding in nature
2. Structure The carbon atom in it forms a tetrahedral structure by joining with 4 carbon and form a three dimensional structure It forms a hexagonal structure by attaching with three other carbon atoms in one dimension only. Likewise, many layers remain attached to each other through weak bonds, so that one layer slides on another layer. Therefore, they are soft
3. Electrical conductance It is insulator electricity but conductor of heat It is a conductor of electricity
4. Uses It is used in making jewellery, cutting glasses, grinding and making holes It is used in pencils, dry cells and electric arcs

Question 7: Write your views in the following table and also discuss with other students.

Advantages of uses of petroleum as fuel Disadvantages of uses of petroleum as fuel

Answer: Check the following table:

Sl. No. Advantages of uses of petroleum as fuel Disadvantages of uses of petroleum as fuel
1. Petroleum is used as a fuel in automobiles and for cleaning/dry washing substances. Petrol and diesel cause a lot of air pollution.
2. These fuels are readily available. Its reserves are on the brink of extinction.
3. These fuels are convenient to use Due to increased use of petroleum fuel, carbon monoxide is formed which is harmful for the environment and a major factor of global warming.

Question 8: The use of petrol, diesel and kerosene is rising day by day. Their smoke is mixing with air and causing air pollution. Write your suggestions and views for reducing air pollution.

Answer: Here are some useful suggestions to control pollution caused due to petroleum usage:

1. Should drive automobiles at moderate speed which cause less air pollution.

2. Petroleum should be judiciously and economically used.

3. People should switch off the engine at traffic signals or places where the waiting time is more.

4. Ensure that the tyre pressure is under constant check.

5. Use lead-free petrol, CNG, LPG to minimise air pollution.

6. Ensure proper maintenance of the vehicle on a regular basis.

7. Sustainable use of petroleum products so that future generations can also use them.

Question 9: List the fuels used in daily life.

Answer: Some of the fuels that we use in our daily lives include wood, coal, dung cakes, agricultural wastes, kerosene, petrol, gasoline, Liquified Petroleum Gas (LPG), biogas, water gas (H2 + CO), coal gas, producer gas (N2 + CO), etc.

Question 10: Draw the diagram of extraction of petrol and label it.

Answer: Given below is the labelled diagram of extraction of petrol:

Extraction of petrol

Extraction of petrol

Question 11: Differentiate between complete and incomplete combustion. Explain with an example.

Answer: Given below are the points of difference between complete and incomplete combustion:

Complete combustion: In a combustion substance, when a sufficient amount of oxygen is supplied, it burns with a blue flame. This is known as complete combustion.

Example: Combustion of LPG (Liquefied Petroleum Gas).

Incomplete combustion: When any burning substance does not have access to sufficient amount of oxygen supply, it burns with a yellow flame. This is known as incomplete combustion.

Example: Burning of wood that causes acute air pollution.

Additional Short Type Answer Questions

Question 1: Define carbonisation.

Answer: The gradual process of coal formation from dead vegetation is known as carbonisation. Carbon is the dominant element of coal. Since it is formed from plants, it is also considered as an organic fuel.

Question 2: Describe inexhaustible and exhaustible natural resources.

Answer: Inexhaustible natural resources are those resources which are available in unlimited quantity and can be used for a very long period of time. These resources are not likely to get exhausted by human activities. For example – sunlight, air, etc.

On the other hand, exhaustible natural resources are those resources which are limited in nature and can get exhausted by human activities within a span of many years. For example – coal, water, minerals, petroleum, etc.

Question 3: What are the useful products that we can obtain from coal?

Answer: Some of the useful products that we can obtain from coal when it is subjected to destructive distillation are coal tar, coke and coal gas, etc.

Question 4: What are the different types of coal on the basis of carbon content?

Answer: Coal is divided into four types on the basis of carbon content in it:

1. Peat (60% Carbon)

2. Lignite (67% Carbon)

3. Bituminous (80% Carbon)

4. Anthracite (90-98% Carbon)

Question 5: Define coke. What are its uses?

Answer: Coke is a very porous, hard and black substance. It is almost like a pure form of carbon. Coke is mainly used in steel manufacture and for extraction of various metals.

Question 6: Explain combustion. List the things necessary for complete combustion.

Answer: A chemical reaction happens when oxygen mixes with other substances to release heat and produce light. This is known as combustion, which happens due to the burning of a substance in the presence of oxygen.

Given below are the three things which are necessary for complete combustion:

1. Supply of oxygen

2. Particular or optimum temperature

3. Burning substance or fuel

Question 7: What is calorific value?

Answer: Calorific value is the amount of heat released by a unit mass of a fuel during complete combustion.

Question 8: What are allotropes? Mention some allotropes of carbon.

Answer: An element that is found in two or more forms with similar chemical properties but distinct physical properties are known as Allotropes. The property of elements are called Allotropes.

Coal, graphite, diamond, lamp black, etc. are all examples of free forms of carbon and all of these different forms of carbon are called allotropes of carbon.

Question 9: Name a fuel that is used in shoe polish and wax paper.

Answer: Paraffin wax is one such fuel which is used in wax, shoe polish and wax paper.

Question 10: Name some places in India where natural gas is formed.

Answer: In India, natural gas is formed are listed below:

1. Offshore of Gujarat

2. Bombay High basin

3. Andhra Pradesh coast (Krishna-Godavari Basin)

4. Tamil Nadu coast (Cauvery Basin)

5. North Eastern states (Assam and Tripura)

Question 11: Define the constituents of crude oil.

Answer: Crude oil consists of many useful fractions which can be obtained by subjecting it to the process of fractional distillation. These include petroleum gas, gasoline, kerosene, diesel, lubricating oils, paraffin wax and asphalt.

Question 12: Name a fuel that is used in chemical reactions.

Answer: Naphtha is used as a fuel in chemical reactions. It gets separated from petroleum at 120°C to 180°C temperature.

Question 13: Define Compressed Natural Gas (CNG).

Answer: Natural gas is a fossil fuel which is obtained from extraction of petrol. Methane is the main gas in it. It is easy in automobiles such as autos, scooters as a fuel. It is stored under high pressure and compressed and filled in cylinders.

Question 14: Explain the composition of LPG.

Answer: Liquified Petroleum Gas (LPG) is mainly a mixture of ethane, propane, butane, isobutane, etc. This gas can be easily liquified at high pressure.

Question 15: What is coal tar?

Answer: Coal tar is also known as Dammar. It gets separated at 600°C temperature. It is the last residual portion of fractional distillation. It is mainly used for construction of roads.

Question 16: What is petroleum also known as?

Answer: Petroleum is also commonly known as liquid gold. It is costlier than gold for every country in the world. It is used in agriculture, communication, transport, industry, etc.

Question 17: What is biomass?

Answer: Biomass is the substance that is present in animals and plants such as agricultural waste, cow dung, wood, etc.

Question 18: What are three states of matter in a fuel?

Answer: Fuel is found in three states of matter:

1. Solid fuel: Example – wood charcoal, cow dung, agricultural waste, etc.

2. Liquid fuel: Example – Petrol, kerosene, diesel, gasoline, etc.

3. Gaseous fuel: Example – Biogas, water gas, coal gas, CNG, LPG, etc.

Question 19: How is petroleum formed?

Answer: Petroleum is formed from the vegetation and organisms of the sea. Due to the geographical disturbances, many animals and plants get buried under the sea. This causes high pressure and temperature and the absence of air, dead plants and animals convert into petroleum and natural gas in due course of time.

Question 20: Where did the first petroleum well of the world drilling take place?

Answer: The first petroleum well of the world drilling took place in Penisiluama, America in the year 1859.

Question 21: Where in India was the first oil storage found?

Answer: In 1867, the first oil storage place was found at Mecum in Assam, India which was almost eight years after the discovery of the first petroleum well of the world.

Additional Long Type Answer Questions

Question 22: Discuss the allotropes of carbon.

Answer: The allotropes of carbon are divided into types:

1. Crystalline allotropes of carbon: These allotropes of carbon which have a particular or specific structure are mainly of crystalline nature. Examples:

(a) Diamond

(b) Graphite

(c) Fullerene

2. Non-crystalline allotropes of carbon: These allotropes of carbon do not have a particular or specific structure or geometry of carbon atoms. Examples:

(a) Coal from wood

(b) Coke

(c) Kajal (Lamp black).

(d) Animal charcoal (Bone charcoal)

Allotropes of carbon

Question 23: Describe the advice given by Petroleum Conservation Research Association (PCRA) for saving petrol.

Answer: The Petroleum Conservation Research Association (PCRA) had advised people to conserve petrol and diesel while driving:

1. Drive the vehicle with constant and medium speed.

2. Switch of the vehicle engine at traffic signals.

3. Ensure to maintain the vehicle properly and keep the air pressure of tyres in absolute condition.

Question 24: Explain fractional distillation.

Answer: Petroleum is extracted from fractional distillation of crude oil. Petrol is a dark brown colour, dense and oily liquid. It is a mixture of many hydrocarbons. Extracted petroleum is a form of crude oil and is not used in the raw form. Petrol comprises various components such as petroleum gas, naphtha, diesel, kerosene, etc. which have different boiling points.

Crude oil is filled in a fractionating column (vertical cylindrical container) and heated slowly. First petroleum gas, then petrol, naphtha, kerosene and diesel change into vapour and move upward in the column, which are then condensed at different levels and collected separately. This process is known as fractional distillation.

We hope that the above mentioned solutions of “RBSE Class 8 Science Chapter 18 Carbon and Fuel” will help students build a strong foundation of the different concepts mentioned in the chapter.

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