NCERT Solutions for Class 8 Science Chapter 6 Combustion and Flame

Edited By Shivani Poonia | Updated on Apr 09, 2025 10:01 AM IST

We use various types of fuels in our day-to-day life, such as the LPG fuel used in the kitchen or petrol, diesel, and CNG in vehicles, wood, which is burnt during winters for warmth, or cow dung cakes that are used for cooking in villages. This NCERT Chapter 4, Class 8, Combustion and Flame, has a detailed discussion on combustion and flame. This chapter includes the different types of combustion, the factors that influence the combustion, the characteristics of flame components involved in the burning process, and the various uses of combustion in our daily lives.

This Story also Contains

Free download combustion and flame class 8 solutions PDF for CBSE exam.
NCERT Solutions For Science Class 8 Chapter 4 Combustion and Flame: Solved Exercise Questions
NCERT Solutions for Class 8 Science Chapter: Combustion and Flame- Preparation Tips.
NCERT Solutions For Class 8 Science- Chapter-Wise
Combustion and Flame Class 8 NCERT : Important Formulas and Points
Combustion And Flame Class 8 Science: Topics
Benefits of NCERT Solutions for Class 8 Science Chapter 4 Combustion and Flame:
Key Features of Class 8 Science Chapter 4 NCERT

NCERT Solutions for Class 8 Science Chapter 6 Combustion and Flame

The NCERT Class 8 Science Solutions Chapter 4 Combustion and Flame are designed by our experienced subject matter experts to offer a systematic approach to these important concepts and help students to develop a clear understanding of complex topics through a series of solved examples and conceptual explanations. These solutions also provide a valuable resource to the students to enhance their performance in board exams. Our subject matter experts ensure that through NCERT solutions, students can gain maximum knowledge of the chapter.

Free download combustion and flame class 8 solutions PDF for CBSE exam.

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NCERT Solutions For Science Class 8 Chapter 4 Combustion and Flame: Solved Exercise Questions

Q 1. List conditions under which combustion can take place.

Answer:

The conditions required for the combustion to take place are:

(a) Presence of oxygen

(b) Presence of inflammable substance (fuel)

Q 2. Fill in the blanks.
(a) Burning of wood and coal causes_________ of air.
(b) A liquid fuel, used in homes, is_________ .
(c) Fuel must be heated to its___________ ___________ before it starts burning.
(d) Fire produced by oil cannot be controlled by__________ .

Answer:

(a) Burning of wood and coal causes pollution of the air.
(b) A liquid fuel used in homes is LPG(Liquefied Petroleum Gas).
(c) Fuel must be heated to its ignition temperature before it starts burning.
(d) The fire produced by oil cannot be controlled by water.

Q 3. Explain how the use of CNG in automobiles has reduced pollution in our cities.

Answer:

Fuels like petroleum and coal release toxic gases like carbon monoxide, carbon dioxide, and sulfur dioxide during combustion. These harmful gases cause pollution and respiratory problems.

Whereas CNG (Compressed Natural Gas) is a clean fuel and produces these harmful gases in very small quantities.

(CNG is methane stored at high pressure!)

Q 4. Compare LPG and wood as fuels.

Answer:

LPG	Wood
It does not produce smoke.	It produces smoke.
It is easy to store and can be easily transported using pipelines.	It takes up a lot of space to store.
It has a low ignition temperature	It has a high ignition temperature
It does not cause environmental pollution	It leaves unburnt carbon particles, causing air pollution
The calorific value is higher.	The calorific value is lower.

Q 5(a). Give reasons.

Water is not used to control fires involving electrical equipment.
Answer:

Water is not used to control fires involving electrical equipment because water, being a good conductor of electricity, may lead the electric current to spread,d causing electric shocks or short-circuits

Q 5(b). Give reasons.

LPG is a better domestic fuel than wood.
Answer:

Wood produces lots of smoke and unburnt carbon particles, which cause respiratory problems. But LPG does not produce these. That's why LPG is a better domestic fuel than wood.

Q 5(c) . Give reasons.

Paper by itself catches fire easily, whereas a piece of paper wrapped around an aluminium pipe does not.

Answer:

Paper has a low ignition temperature and hence catches fire easily. But when it is wrapped around an aluminium pipe, heat is transferred to the metal, and hence the ignition temperature of the paper is not reached. That is why paper by itself catches fire easily, whereas a piece of paper wrapped around an aluminium pipe does not.

Q 6. Make a labelled diagram of a candle flame.

Answer:

Following is the labelled diagram of a candle flame:

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Q 7. Name the unit in which the calorific value of a fuel is expressed.

Answer:

The calorific value of a fuel is expressed in kilojoules per kilogram (kJ/kg).

Q 8. Explain how CO2 is able to control fires.

Answer:

CO2 is heavier than O2 . Therefore, it acts as a blanket over the substance and cuts off the oxygen supply required for combustion. This way CO2 is able to control fires.

Q 9. It is difficult to burn a heap of green leaves but dry leaves catch fire easily. Explain.
Answer:

It is difficult to burn a heap of green leaves but dry leaves catch fire easily because green leaves have moisture present in them. Hence the heat gets absorbed by water to provide energy to evaporate. But, the dry leaves have no moisture and hence the heat is not lost. That is why it catches fire easily.

Q 10. Which zone of a flame does a goldsmith use for melting gold and silver and why?

Answer:
The goldsmith uses the outermost non-luminous (blue) zone for melting gold and silver. This is because it is the hottest part of the flame and hence melts the metals easily.

Q 11. In an experiment 4.5 kg of a fuel was completely burnt. The heat produced was measured to be 180,000 kJ.Calculate the calorific value of the fuel.

Answer:

The calorific value of the fuel is the amount of heat produced by the complete combustion of 1 kg of fuel.

Given, Heat produced by 4.5 kg of fuel = 180000 kJ

∴ Heat produced by 1 kg of fuel = 180,000 kJ/4.5 Kg = 40,000 kJ

∴ The calorific value of the fuel is 40,000 kJ/kg.

Q 13. Abida and Ramesh were doing an experiment in which water was to be heated in a beaker. Abida kept the beaker near the wick in the yellow part of the candle flame. Ramesh kept the beaker in the outermost part of the flame. Whose water will get heated in a shorter time?

Answer:

The outermost part of the flame is the hottest region of the flame. Hence, water kept near it will get heated faster, i.e, in a shorter time.
Therefore, the water in Ramesh's beaker will get heated in a shorter time.

NCERT Solutions for Class 8 Science Chapter: Combustion and Flame- Preparation Tips.

In order to prepare this chapter, first read the NCERT Class 8 Science chapter 4, Combustion and Flame. Once you are done with the chapter reading, prepare the NCERT Science Class 8 chapter 4 Combustion and Flame notes and revise them properly. After proper revision, go for the NCERT Science Class 8 chapter 4 Combustion and Flame worksheets. For better preparation, attempt as many NCERT quizzes for Science Class 8 chapter 4 as possible. As far as NCERT preparation is concerned, a great understanding of NCERT solutions for the Science Class 8 chapter 4, Combustion and Flame, can be useful for you.

NCERT Solutions For Class 8 Science- Chapter-Wise

Apart from combustion and flame class 8 ncert solutions, chapter-wise solutions are given below for science class 8.

Chapter 1	Crop Production and Management
Chapter 2	Microorganisms Friend and Foe In Microorganisms
Chapter 3	Coal and Petroleum
Chapter 4	Combustion and Flame
Chapter 5	Conservation of Plants and Animals
Chapter 6	Reproduction in Animals
Chapter 7	Reaching the Age of Adolescence
Chapter 8	Force and Pressure
Chapter 9	Friction
Chapter 10	Sound
Chapter 11	Chemical Effects of Electric Current
Chapter 12	Some Natural Phenomena
Chapter 13	Light

Combustion and Flame Class 8 NCERT : Important Formulas and Points

Combustion

Combustion is a chemical process in which a substance reacts with oxygen to produce heat and light.
Requirements for Combustion: For combustion to occur, three things are needed: fuel, oxygen, and heat. This is often referred to as the "fire triangle.

Fuel + Oxygen → Carbon Dioxide + Water + Heat + Light

Combustible and Non-Combustible Substances

Combustible substances can burn when exposed to heat or a flame, while non-combustible substances do not readily catch fire and burn. Examples of combustible materials include wood and gasoline, while non-combustible materials include metals and glass.

Flame

A flame is a visible gaseous part of a fire. It is the region where combustion occurs, and it emits heat and light.

Structure of a Flame

A flame has three zones:

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Inner Zone: This is the hottest part of the flame, where complete combustion occurs, and it appears blue.
Middle Zone: In this zone, combustion is incomplete, and it appears yellow.
Outer Zone: The outermost zone contains unburnt fuel, which makes it less hot and less bright.

Types of Flames

Flames can be classified into different types based on the type of fuel and the conditions of combustion. Examples include a blue flame from a Bunsen burner (complete combustion) and a yellow flame from a candle (incomplete combustion).

Fire Safety

Fire safety measures include using fire extinguishers, keeping flammable materials away from open flames, and having fire escape plans in place.

Control of Combustion

Controlling combustion involves regulating the supply of fuel, oxygen, and heat.

Adjusting the air supply can change the colour and temperature of a flame.

Smoke

Smoke is produced during incomplete combustion and consists of tiny unburnt particles and harmful gases like carbon monoxide.

Fire Extinguishers

Fire extinguishers are devices used to control small fires by cutting off the supply of oxygen or cooling the fire. Different types of fire extinguishers are designed for specific types of fires, such as water extinguishers for ordinary fires and CO2 extinguishers for electrical fires.

Combustion And Flame Class 8 Science: Topics

Topics for class 8 science chapter 4 question answer given below:

What is combustion
How do we control fire
Types of combustion
Flame
Structure of a flame
What is fuel
Fuel efficiency

NCERT Solutions For Class 8: Subject-Wise

Benefits of NCERT Solutions for Class 8 Science Chapter 4 Combustion and Flame:

Homework, as well as revision, becomes an easy task with the NCERT Solutions for Class 8 Science chapter 4, Combustion and Flame, in hand.
Similar type questions in the class 8 science chapter 4 question answer are expected in the class exams. This is where the NCERT solutions for Class 8 Science chapter 4, Combustion and Flame, are important.
You can score well in the exam with the help of these solutions of NCERT for Class 8 Science Chapter 4 Combustion and Flame.

Key Features of Class 8 Science Chapter 4 NCERT

Comprehensive Coverage: The class 8 combustion and flame ncert solutions provide comprehensive coverage of the chapter, addressing all important topics and concepts related to combustion and flames.
Step-by-Step Explanations: Each question is explained step by step, making it easier for students to understand the combustion and flame class 8 questions and answers and apply the concepts.
Clarity in Language: The Class 8 science chapter 4 question answers are written in clear and concise language, ensuring that students can grasp the explanations easily.
Conceptual Clarity: These solutions focus on building a strong conceptual understanding of combustion and flames, helping students develop a solid foundation in the subject.
Exam Preparation: The combustion and flame class 8 solutions serve as valuable resources for exam preparation, allowing students to practice and improve their performance in Class 8 Science exams.
Chapter Renumbering: Note that "Combustion and Flame" has been renumbered as Chapter 4 in the CBSE Syllabus for 2025-26.

Also, check the NCERT Books and the NCERT Syllabus here:

Frequently Asked Questions (FAQs)

1. What are some common causes of fire hazards in the home?

Common causes of fire hazards in homes are given below:

Improperly stored flammable liquids, Careless smoking, Unattended cooking, Faulty electrical wiring, Lack of working smoke detectors, Unattended candles, Overloaded electrical outlets.

2. Write the different zones in a candle flame. What are they?

A candle flame has three main zones, which are given below:

Zone 3 (Non-Luminous Zone): It is the outermost zone. It is almost invisible and the hottest part of the flame. With sufficient oxygen, Complete combustion occurs here.

Zone 2 (Luminous Zone): It is the middle zone, which is typically yellow and bright. Incomplete combustion occurs here.

Zone 1 (Dark Inner Zone): It is the innermost zone closest to the wick. It is the coolest part of the flame, where combustion doesn't occur. It also contains unburnt fuel vapor.

3. What is the definition of combustion?

Combustion: It is a chemical process that involves rapid reaction between a substance and an oxidant (usually oxygen) to produce heat and light.

4. How can a fire be extinguished?

Fire can be extinguished by removing one or more elements of the fire triangle:

Removing the oxygen: Smothering the fire with a foam, blanket, or carbon dioxide.

Removing the heat: Cooling the burning material with water or another coolant material.

Removing the fuel: Physically removing unburnt fuel or letting the fuel burn completely.

5. What is the ignition temperature?

Ignition temperature is the minimum temperature required to initiate combustion, without any external spark or flame. It is also called the autoignition temperature.

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Option 1) $0.34\; J$	Option 2) $0.16\; J$
Option 3) $1.00\; J$	Option 4) $0.67\; J$

A person trying to lose weight by burning fat lifts a mass of 10 kg upto a height of 1 m 1000 times. Assume that the potential energy lost each time he lowers the mass is dissipated. How much fat will he use up considering the work done only when the weight is lifted up ? Fat supplies 3.8×10⁷J of energy per kg which is converted to mechanical energy with a 20% efficiency rate. Take g = 9.8 ms⁻² :

Option 1)

2.45×10⁻³ kg

Option 2)

6.45×10⁻³ kg

Option 3)

9.89×10⁻³ kg

Option 4)

12.89×10⁻³ kg

An athlete in the olympic games covers a distance of 100 m in 10 s. His kinetic energy can be estimated to be in the range

Option 1) $2,000 \; J - 5,000\; J$	Option 2) $200 \, \, J - 500 \, \, J$
Option 3) $2\times 10^{5}J-3\times 10^{5}J$	Option 4) $20,000 \, \, J - 50,000 \, \, J$

A particle is projected at 60⁰ to the horizontal with a kinetic energy $K$ . The kinetic energy at the highest point

Option 1) $K/2\,$	Option 2) $\; K\;$
Option 3) $zero\;$	Option 4) $K/4$

In the reaction,

$2Al_{(s)}+6HCL_{(aq)}\rightarrow 2Al^{3+}\, _{(aq)}+6Cl^{-}\, _{(aq)}+3H_{2(g)}$

Option 1) $11.2\, L\, H_{2(g)}$ at STP is produced for every mole $HCL_{(aq)}$ consumed	Option 2) $6L\, HCl_{(aq)}$ is consumed for ever $3L\, H_{2(g)}$ produced
Option 3) $33.6 L\, H_{2(g)}$ is produced regardless of temperature and pressure for every mole Al that reacts	Option 4) $67.2\, L\, H_{2(g)}$ at STP is produced for every mole Al that reacts .

How many moles of magnesium phosphate, $Mg_{3}(PO_{4})_{2}$ will contain 0.25 mole of oxygen atoms?

Option 1) 0.02	Option 2) 3.125 × 10^-2
Option 3) 1.25 × 10^-2	Option 4) 2.5 × 10^-2

If we consider that 1/6, in place of 1/12, mass of carbon atom is taken to be the relative atomic mass unit, the mass of one mole of a substance will

Option 1) decrease twice	Option 2) increase two fold
Option 3) remain unchanged	Option 4) be a function of the molecular mass of the substance.

With increase of temperature, which of these changes?

Option 1) Molality	Option 2) Weight fraction of solute
Option 3) Fraction of solute present in water	Option 4) Mole fraction.

Number of atoms in 558.5 gram Fe (at. wt.of Fe = 55.85 g mol^-1) is

Option 1) twice that in 60 g carbon	Option 2) 6.023 × 10²²
Option 3) half that in 8 g He	Option 4) 558.5 × 6.023 × 10²³

A pulley of radius 2 m is rotated about its axis by a force F = (20t - 5t²) newton (where t is measured in seconds) applied tangentially. If the moment of inertia of the pulley about its axis of rotation is 10 kg m² , the number of rotations made by the pulley before its direction of motion if reversed, is