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NCERT Solutions for Class 8 Science Chapter 6 Combustion and Flame

NCERT Solutions for Class 8 Science Chapter 6 Combustion and Flame

Edited By Vishal kumar | Updated on Sep 16, 2023 12:12 PM IST

NCERT Solutions for Class 8 Science Chapter 6 – Access and Download Free PDF

NCERT Solutions for Class 8 Science Chapter 6 Combustion and Flame- In the NCERT Class 8 Science book, chapter 6 is Combustion and Flame. A thorough study of the chapter exercises and solutions of NCERT for Class 8 Science Chapter 6 Combustion and Flame will be beneficial for Class 8 students as concept-based questions are asked from this chapter in exams. Before studying the chapter, you must know that in your day-to-day life, you use various types of fuels. Be it the LPG fuel used in the kitchen or petrol, diesel, CNG in-vehicle, be it wood which is burnt during winters for warmth or cow dung cakes that are used for cooking in villages.

The NCERT solutions for Class 8 Science Chapter 6 Combustion and Flame are prepared by our subject experts so that students use these solutions to learn the concepts in minimal time. All these fuels work on the same phenomenon which is burning. NCERT Science Class 8 Chapter 6 Combustion and Flame deals with the chemical process of burning or combustion. It also deals with the details of burning without a flame. After studying the chapter thoroughly, you will be able to attempt the exercise of NCERT textbook and get the correct CBSE NCERT solutions for Class 8 Science chapter 6 Combustion and Flame. For middle school students, a tool like NCERT Solutions helps extremely in their studies to score decent marks in their examinations.

While studying NCERT Science chapter 6 you will also get to know what are combustible and non-combustible materials.

**As per the CBSE Syllabus 2023-24, this chapter has been renumbered as Chapter 3 in Class 8 Science.

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

NCERT Solutions for Class 8 Science Chapter 6 Combustion and Flame

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NCERT Solutions For Science Class 8 Chapter 6 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 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 air.
(b) A liquid fuel, used in homes is LPG(Liquified 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 sulphur 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 quantity.

(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 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 un-burnt carbon particles causing air pollution
Calorific value is higher.
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 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. Thats 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:

1659447799453

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 CO_{2} is able to control fires.

Answer:

CO_{2} is heavier than O_{2} . Therefore, it acts as a blanket over the substance and cuts off the oxygen supply required for combustion. This way CO_{2} 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

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

\therefore 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 6 Combustion and Flame- Preparation Tips.

In order to prepare this chapter firstly read the NCERT Class 8 Science chapter 6 Combustion and Flame. Once you are done with the chapter reading, prepare NCERT Science Class 8 chapter 6 Combustion and Flame notes and revise them properly. After proper revision, go for NCERT Science Class 8 chapter 6 Combustion and Flame worksheets. For better preparation, attempt as many NCERT quizzes for Science Class 8 chapter 6 as possible. As far as NCERT preparation is concerned, a great understanding of NCERT solutions for Science Class 8 chapter 6 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 solution are given below for science class 8.

Combustion and Flame Class 8 NCERT Solutions: 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 Chapter 6-Topics

Topics for class 8 science chapter 6 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 6 Combustion and Flame:

  • Homework, as well as revision, becomes an easy task with the NCERT Solutions for Class 8 Science chapter 6 Combustion and Flame in hand.
  • Similar type questions in the class 8 science chapter 6 question answer are expected in the class exams. This is where the NCERT solutions for Class 8 Science chapter 6 Combustion and Flame is important.
  • You can score well in the exam with the help of these solutions of NCERT for Class 8 Science Chapter 6 Combustion and Flame.

Key Features of Class 8 Science Chapter 6 NCERT Solutions

  1. 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.

  2. 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.

  3. Clarity in Language: The class 8 science ch 6 question answer are written in clear and concise language, ensuring that students can grasp the explanations easily.

  4. Conceptual Clarity: These solutions focus on building a strong conceptual understanding of combustion and flames, helping students develop a solid foundation in the subject.

  5. 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.

  6. Chapter Renumbering: Note that Chapter 6, "Combustion and Flame," has been renumbered as Chapter 3 in the CBSE Syllabus for 2023-24.

Also Check NCERT Books and NCERT Syllabus here:

Frequently Asked Question (FAQs)

1. What is combustion?

Combustion is a chemical process that involves the reaction of a substance with oxygen in order to give away heat. The substance that undergoes combustion is known as fuel. Fuels can be   

  1.    Solid   
  2.    Liquid   
  3.    Gas   

   In NCERT Science Class 8 Chapter 6 you will majorly learn about these fuels and the process of combustion. On the basis of combustion, materials can be divided into two types   

  1.    Combustible materials   
  2.    Non- combustible materials  
2. What is the ignition temperature?

 Have ever these questions crossed your mind   

  1.    Why LPG burns so fast while CNG takes some time?   
  2.    Why kerosene is required to burn wood?   

   The answers to these above-stated questions lie in their ignition temperatures.  It refers to the minimum temperature at which a substance catches fire. Now you can try attempting the above questions. As you will gradually go about the NCERT chapter 6 combustion and flame you will get familiar with the ignition temperature of various substances and how it is important for combustion.

3. What are the topics covered in NCERT Class 8 Science Chapter 6?

Here are the topics covered in NCERT Class 8 Science chapter 6

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

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A block of mass 0.50 kg is moving with a speed of 2.00 ms-1 on a smooth surface. It strikes another mass of 1.00 kg and then they move together as a single body. The energy loss during the collision is

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 3.8×107 J 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

Option 1)

less than 3

Option 2)

more than 3 but less than 6

Option 3)

more than 6 but less than 9

Option 4)

more than 9

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