NCERT Solutions For Class 8 Science Chapter 6 Combustion and Flame

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Class 8 Science Chapter 6 Combustion and Flame

NCERT Solutions For Class 8 Science Chapter 6 Combustion And Flame, (Science) exam are Students are taught thru NCERT books in some of state board and CBSE Schools.  As the chapter involves an end, there is an exercise provided to assist students prepare for evaluation.  Students need to clear up those exercises very well because the questions withinside the very last asked from those. 

Sometimes, students get stuck withinside the exercises and are not able to clear up all of the questions.  To assist students solve all of the questions and maintain their studies without a doubt, we have provided step by step NCERT Solutions for the students for all classes.  These answers will similarly help students in scoring better marks with the assist of properly illustrated Solutions as a way to similarly assist the students and answering the questions right.

NCERT Solutions For Class 8 Science Chapter 6 Combustion and Flame

Class 8 Science Chapter 6 Combustion and Flame

Exercise Questions

1. List conditions under which combustion can take place.

Solution:

The burning of a substance in the presence of oxygen is defined as combustion.

The conditions under which combustion can take place are

  • The presence of air or oxygen.
  • The presence of fuel plays a significant role.
  • Ignition temperature is maintained (It is defined as the substance that catches fire at its lowest temperature.)

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) The fire produced by oil cannot be controlled by___________ .

Solution:

(a) Burning of wood and coal causes Pollution of air.

(b) A liquid fuel, used in homes is Kerosene.

(c) Fuel must be heated to its Ignition Temperature before it starts burning.

(d) The fire produced by oil cannot be controlled by Water.

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

Solution:

CNG played an important role in reducing pollution among automobiles for the following reasons

  • CNG is comparatively a cleaner fuel.
  • The CNG can be an alternative for diesel, petrol and propane/LPG.
  • It usually contains a few undesirable gases than the other fuels mentioned above.
  • The combustion of fuels like petroleum causes many unburnt carbon particles along with carbon monoxide, which leads to respiratory diseases.

4. Compare LPG and wood as fuels

Solution:

Wood

  • It is considered as a traditional fuel used for both domestic and industrial purposes.
  • Wood produces a lot of smoke which pollutes the atmosphere and cause respiratory diseases.
  • The usage of wood to a large extent causes deforestation.
  • The calorific value of wood ranges between 17000 to 22000 kJ/kg
  • However, wood may be used as a furnace, stove or fireplace indoors while it is used for a campfire, furnace outdoors.

      LPG

  • The usage LPG (Liquefied petroleum gas) has replaced wood.
  • It doesn’t release smoke and other pollutants.
  • It is a cleaner fuel.
  • The fuel efficiency of LPG is more than that of wood.
  • The calorific value of LPG is 55000 kJ/kg.
  • Hence, LPG is the most preferred choice.

5. Give reasons.

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

(b) LPG is a better domestic fuel than wood.

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

Solution:

a)

  • Water is a good conductor of electricity.
  • If added to an electrical fire, the water would just spread the electricity further.
  • The person dousing the fire might get an electric shock

b)

  • LPG being a cleaner fuel than wood doesn’t release smoke and other pollutants.
  • Wood, on the other hand, releases a lot of smoke and fumes polluting the atmosphere causing pollution and leading to respiratory diseases.
  • Hence, LPG is a better domestic fuel than wood.

c)

  • The paper by itself catches fire easily because of its low ignition temperature.
  • The piece of paper wrapped around an aluminium pipe doesn’t catch fire because aluminium is a good conductor of electricity.
  • While the paper wrapped around an aluminium pipe results in an increase in ignition temperature. So, there is a transfer of heat from paper to the aluminium pipe. Hence it doesn’t catch fire.

6. Make a labelled diagram of a candle flame.

Solution:

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

Solution:

Calorific value is defined as the energy contained in the fuel. It is expressed in the form kJ/kg

kJ=kilo joules

kg=kilogram

8. Explain how CO2 is able to control fires.

Solution:

CO2 is a non-combustible gas and extinguishes fire in two ways:

(i) It is heavier than oxygen and it covers the fire like a blanket and cuts off the contact between oxygen and fuel.

(ii) In cylinders, CO2 is kept in the liquid form. When released, it expands enormously. This brings down the temperature of the fuel, which helps in controlling the fire.

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

Solution:

A heap of green leaves contains a lot of moisture in it, hence its ignition temperature is high. Therefore, it does not catch fire easily.

But dry leaves have no moisture content in it, hence its ignition temperature is low. Therefore, it catches fire easily.

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

Solution:

The goldsmith mainly uses non-luminous flame which is termed to be the outermost part of the flame. This part of the flame is used because the outermost flame undergoes complete combustion and is considered as the hottest part of the flame.

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.

Solution:

12. Can the process of rusting be called combustion? Discuss.

Solution:

No, because rusting is an exothermic process as heat is liberated during rusting. On the other hand, combustion is a chemical process in which a substance reacts with oxygen to release energy in the form of heat or light.

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?

Solution:

The water placed in the outermost part of the flame will be heated in a short time since it is a non-luminous flame and is regarded as the hottest part of the flame. So Ramesh’s beaker will be heated first. However, Abida who placed the beaker in the luminous flame (yellow flame) is comparatively less hot.

Benefits of NCERT Solutions for Class 8

NCERT Solutions for Class 8 contains extremely important points, and for each chapter, each concept has been simplified to make it easier to remember and increase your chances of achieving excellent exam results. Exam Preparation References Here are some tips on how these Solutions can help you prepare for the exam.

  1. This helps students solve many of the problems in each chapter and encourages them to make their concepts more meaningful.
  2. NCERT Solutions for Class 8 encourage you to update your knowledge and refine your concepts so that you can get good results in the exam.
  3. These NCERT Solutions For Class 8 are the best exam materials, allowing you to learn more about your week and your strengths. To get good results in the exam, it is important to overcome your weaknesses.
  4. Most of the questions in the exam are formulated in a similar way to NCERT textbooks. Therefore, students should review the Solutions in each chapter in order to better understand the topic.
  5. It is free of cost.

Tips & Strategies for Class 8 Exam Preparation

  1. Plan your course and syllabus and make time for revision
  2. Please refer to the NCERT Solutions available on the cbsestudyguru website to clarify your concepts every time you prepare for the exam.
  3. Use the cbsestudyguru learning app to start learning to successfully pass the exam. Provide complete teaching materials, including resolved and unresolved tasks.
  4. It is important to clear all your doubts before the exam with your teachers or Alex (an Al study Bot). 
  5. When you read or study a chapter, write down algorithm formulas, theorems, etc., and review them quickly before the exam.
  6. Practice an ample number of question papers to make your concepts stronger. 
  7. Take rest and a proper meal.  Don’t stress too much. 

Why opt for cbsestudyguru NCERT Solutions for Class 8 ? 

  • cbsestudyguru provide NCERT Solutions for all subjects at your fingertips.
  • These Solutions are designed by subject matter experts and provide Solutions to every NCERT textbook questions. 
  • cbsestudyguru especially focuses on making learning interactive, effective and for all classes.
  • We provide free NCERT Solutions for class 8 and all other classes.

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