NCERT Solutions for Class 8 Science Chapter 6 - Combustion And Flames

1. List Conditions Under Which Combustion Can Take Place.

Ans: Combustion takes place under the following three conditions: 

(i) In the presence of fuel.

(ii) In the presence of oxygen (air).

(iii) In the presence of heat - the minimum temperature at which a substance catches fire, known as ignition temperature.

2. Fill in the Blanks:

a) Burning of wood and coal causes ______ of air.

Ans: Burning of wood and coal causes pollution of air.

b) A liquid fuel used in homes is _____.

Ans: A liquid fuel used in homes is Liquified Petroleum Gas (LPG).

c) Fuel must be heated to its ____ before it starts burning.

Ans: Fuel must be heated to its ignition temperature before it starts burning.

d) The fire produced by oil cannot be controlled by _____.

Ans: Fire produced by oil cannot be controlled by water.

3. Explain How the Use of CNG in Automobiles Has Reduced Pollution in Our Cities.

Ans: The use of CNG in automobiles has reduced pollution in our cities because it is a clean fuel and the amount of unburnt fuel in CNG is very less compared to petroleum. It does not produce smoke and harmful substances that are produced in petroleum.

4. Compare LPG and Wood as Fuels.

Ans: The difference between LPG and wood as fuels is: 

5. Give Reasons.

a) Water is not used to control fires involving electrical equipment.

Ans: Water is not used to control fires involving electrical equipment because water is a good conductor of electricity due to which the person may be electro-conducted and it may damage the equipment.

b) LPG is a better domestic fuel than wood.

Ans: LPG is a better domestic fuel than wood because wood produces a lot of smoke on combustion and causes respiratory problems. Also, its efficiency is lower than LPG.

c) Paper by itself catches fire easily whereas a piece of paper wrapped around an aluminum pipe does not.

Ans: Paper by itself catches fire easily whereas a piece of paper wrapped around an aluminum pipe does not because aluminum is a good conductor of heat which absorbs the heat from the paper and the paper does not catch fire. Whereas, the paper by itself catches fire.

6. Make a Labeled Diagram of a Candle Flame.

Ans: A labeled diagram of a candle flame is: 

7. Name the Unit in Which the Calorific Value of a Fuel is Expressed.

Ans: “Kilo Joule per Kilogram $\left( kJ/kg \right)$” is used to express the calorific value of a fuel.

8. Explain how \[\mathbf{C}{{\mathbf{O}}_{\mathbf{2}}}\] is able to control fires.

Ans: We know that combustion takes place under the following three conditions: 

(i) In the presence of oxygen (air).

(ii) In the presence of fuel.

(iii) In the presence of heat - the minimum temperature at which a substance catches fire, known as ignition temperature.

We can control the fire if any one of the three conditions is not met. 

(i) $C{{O}_{2}}$ is heavier than oxygen and hence it acts as a protective blanket and prevents oxygen from reaching the fire.

(ii) Since $C{{O}_{2}}$ is stored in a liquid state, therefore, when it is used on the fire, it expands and cools which lowers down the temperature. This prevents heat from reaching the fire.

9. It is Difficult To Burn a Heap of Green Leaves, but Dry Leaves Catch Fire Easily. Explain.

Ans: It is difficult to burn a heap of green leaves, but dry leaves catch fire easily because combustion takes place in the presence of heat - the minimum temperature at which a substance catches fire, known as ignition temperature. Green leaves have high moisture than dry leaves and hence, it takes more time for green leaves to reach ignition temperature than dry leaves.

10. Which Zone of a Flame Does a Goldsmith Use for Melting Gold and Silver and Why?

Ans: Goldsmiths use the outermost zone of the flame to melt gold and silver because gold and silver have a high melting point and the outermost part undergoes complete combustion and it is the hottest part of the flame which supply the adequate amount of heat required for melting. 

11. In an Experiment \[\mathbf{4}.\mathbf{5}\text{ }\mathbf{kg}\] of a fuel was completely burnt. The heat produced was measured to be \[\mathbf{180},\mathbf{000}\text{ }\mathbf{kJ}\]. Calculate the calorific value of the fuel.

Ans: The amount of heat released during combustion of $1\text{ }kg$ fuel is known as calorific value i.e., 

$Calorific\text{ }Value=\dfrac{Heat\text{ produced during combustion}}{Quantity\text{ of fuel}}$  

$\Rightarrow Calorific\text{ }Value=\dfrac{180,000}{4.5}\text{ }kJ/kg$

$\therefore Calorific\text{ }Value=40,000\text{ }kJ/kg$

12. Can the Process of Rusting Be Called Combustion? Discuss.

Ans: A chemical process in which a substance reacts with oxygen to give off heat is called combustion. When an iron metal combines with the oxygen in the presence of water to form a compound iron oxide is known as rusting. 

Therefore, the process of rusting can be called combustion because in both processes, heat, and light are produced. Rusting is known as slow combustion. 

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?

Ans: A labeled diagram of a candle flame is: 

(Image will be uploaded soon)

Observe that the innermost zone of the candle which is near to the wick is the least hot whereas the outer zone of the candle is the hottest part of the candle flame.

Since Ramesh kept the beaker in the outermost part of the flame, therefore his beaker will be heated in a shorter time as compared to Abida. 

Combustion and Flame Class 8 NCERT Solutions PDF Download

The free Class 8 Science Chapter 6 PDF download for NCERT solutions will help you to gain an in-depth insight into Chemistry. The topics covered in ch 6 Science Class 8 NCERT solutions are an important part of the syllabus. NCERT Solutions provide an easy outlook on the topic and helps the student to secure good marks in their exams. The NCERT solutions of Class 8 Science Chapter 6 can be found online for download in a PDF form. It is easy to understand and will clarify all doubts the students can have.

NCERT Solutions for Combustion and Flame Class 8 Science Chapter 6

NCERT Solutions for Class 8 Science Chapter 6 Combustion and Flame provide a clear insight into tackling combustion with the help of CNG instead of other fuels. Comparatively, CNG is a cleaner fuel. The CNG can be an option for diesel, petroleum and propane/LPG. For most of the parts, it contains a couple of bothersome gases than different energies referenced previously. The burning of fuels like oil causes numerous unburnt carbon particles alongside carbon monoxide, which prompts respiratory infections.

The solutions provided in this PDF also cover the following topics. Water is a decent conduit of power. Whenever added to an electrical fire, the water would simply spread the power further. The individual drenching the fire may get an electric stun. LPG being a cleaner fuel than wood, doesn't deliver smoke and different contaminations. Wood, then again, delivers a great deal of smoke and exhaust dirtying the environment, making contamination and driving respiratory ailments.

Consequently, LPG is a superior homegrown fuel than wood. The paper without anyone else bursts into flames effectively due to its low start temperature. The bit of paper folded over an aluminium pipe doesn't burst into flames since aluminium is a decent channel of power. At the same time, the paper folded over an aluminium pipe brings about an expansion in start temperature. In this way, there is an exchange of warmth from paper to the aluminium pipe. Thus it doesn't burst into flames. These solutions cater to all the needs a student can have regarding this topic.

NCERT Class 8 Science Chapter 6 Solution Weightage Marks

Class 8 Science Chapter 6 Solution contains a total of 10 marks in CBSE examinations. The topics included in NCERT Solutions for Class 8 Science ch 6 are as follows:

• Combustion.

• Flame Solutions.

• Types of Combustions.

• Role of Oxygen in Combustion.

• Ignition Temperatures.

• Inflammable Substances. 

• Control of Fire.

• Fuel and its Efficiency.

• Definitions and Different zones of Flames.

• Dangerous Pollutants.

• Acid Rain and its Effects.

Benefits of NCERT Solutions For Class 8 Science Chapter 6 Combustion and Flame

The benefits of NCERT Class 8 Science Chapter 6 are endless. The solutions will clear doubts for every candidate, and all prospective questions on these topics are answered here. Combustion and Flame Class 8 NCERT Solutions provide a clear insight into Combustion and Flame. These solutions are given in simple language and can be understood by all students. The solutions are given by teachers who are regarded as experts on this subject. These are prepared with the sole objective of helping the students to gain the maximum marks on these topics. The solutions also contain practical examples of ch 6 Science Class 8 so that the students can handle any problem without any difficulty in the subject. All probable topics that can appear in the exams are covered thoroughly in these solutions for the students to gain more marks in the examination.

Chapter wise NCERT Solutions for Class 8 Science

• Chapter 1 - Crop Production and Management

• Chapter 2 - Microorganisms : Friend and Foe

• Chapter 3 - Synthetic Fibres and Plastics

• Chapter 4 - Materials : Metals and Non-Metals

• Chapter 5 - Coal and Petroleum

• Chapter 6 - Combustion and Flame

• Chapter 7 - Conservation of Plants and Animals

• Chapter 8 - Cell - Structure and Functions

• Chapter 9 - Reproduction in Animals

• Chapter 10 - Reaching The Age of Adolescence

• Chapter 11 - Force and Pressure

• Chapter 12 - Friction

• Chapter 13 - Sound

• Chapter 14 - Chemical Effects of Electric Current

• Chapter 15 - Some Natural Phenomena

• Chapter 16 - Light

• Chapter 17 - Stars and The Solar System

• Chapter 18 - Pollution of Air and Water