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NCERT Solutions for Class 8 Science Chapter 4 Combustion and Flame
Edited By Shivani Poonia | Updated on Jun 05, 2025 11:04 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. Class 8 Science NCERT chapter 4 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
- Practice questions for Class 8 Science Combustion and Flame
- Topics Of Combustion And Flame Class 8 Science
- Combustion and Flame Class 8 NCERT: Important Formulas and Points
- 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-Wise
Solutions of NCERT are designed by our subject experts in a very detailed and comprehensive manner, which offers a systematic approach to these important concepts and helps students to develop a clear understanding of complex topics through a series of solved examples and conceptual explanations. Class 8 Science chapter 4 solutions also provide a valuable resource to 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.
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)
(c) Maintain Ignition Temperature (the minimum temperature at which a substance catches fire).
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:
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LPG
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Wood
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It does not produce smoke.
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It produces smoke.
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It is easy to store and can be easily transported using pipelines.
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It takes up a lot of space to store.
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It has a low ignition temperature
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It has a high ignition temperature
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It does not cause environmental pollution
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It leaves unburnt carbon particles, causing air pollution
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The calorific value is higher.
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The calorific value is lower.
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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:
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.
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.
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.
Practice questions for Class 8 Science Combustion and Flame
Question 1: What is Combustion?
Answer 1: It is a Chemical process in which a substance reacts with oxygen to produce light and Heat. Another name for this process is burning.
Question 2: What are inflammable substances?
Answer 2: These are those substances that can catch fire easily at room temperature. Examples are Petroleum, LPG, and Alcohol.
Question 3: What are the essential requirements for combustion?
Answer 3: The essential requirements for combustion are:
- Fuel
- Oxygen
- Heat
Question 4: What is the ignition Temperature?
Answer 4: It is the minimum temperature required by any substance to catch fire and start burning.
Question 5: What are the different zones of a candle flame?
Answer 5: A Candle flame has 3 significant zones:
1) Outer zone
- It is the hottest zone and blue, which is due to complete combustion.
2) Middle zone
- This is yellow and luminous due to partial combustion.
3) Inner zone
- This zone is the least hot and darkest, which is due to the presence of unburnt wax vapours.
Topics Of Combustion And Flame Class 8 Science
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
Combustion and Flame Class 8 NCERT: Important Formulas and Points
Combustion
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Combustion is a chemical process in which a substance reacts with oxygen to produce heat and light.
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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.
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Middle Zone: In this zone, combustion is incomplete, and it appears yellow.
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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.
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.
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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.
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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.
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Conceptual Clarity: These solutions focus on building a strong conceptual understanding of combustion and flames, helping students develop a solid foundation in the subject.
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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.
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Chapter Renumbering: Note that "Combustion and Flame" has been renumbered as Chapter 4 in the CBSE Syllabus for 2025-26.
NCERT Solutions For Class 8 Science- Chapter-Wise
Apart from the combustion and flame class 8 NCERT solutions, chapter-wise solutions are given below for the science class 8.
NCERT Solutions For Class 8: Subject-Wise
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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