NCERT Solutions for Class 8 Science Science - NCERT Solution Chapter 6

Combustion and Flame Class 8

Chapter 6 Combustion and Flame Exercise Solutions

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Exercise : Solutions of Questions on Page Number : 75

Q1 :  

List conditions under which combustion can take place.


Answer :

Combustion is a process of reaction of a substance with oxygen. There are certain conditions required for combustion to take place. They are:

(i) Presence of a fuel

(ii) Air (or oxygen)

(iii) Ignition temperature (minimum temperature at which a substance catches fire)

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Q2 :  

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 __liquefied petroleum gas (LPG)_.

(c) Fuel must be heated to its __ignition temperature__ before it starts burning.

(d) Fire produced by oil cannot be controlled by __water__.

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Q3 :  

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


Answer :

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Q4 :  

Compare LPG and wood as fuels.


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Q5 :  

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.


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Q6 :  

Make a labelled diagram of a candle flame.


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Q7 :  

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


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Q8 :  

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


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Q9 :  

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


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Q10 :  

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.


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Q11 :  

Can the process of rusting be called combustion? Discuss.


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Q12 :  

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?


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<< Previous Chapter 5 : Coal and Petroleum Next Chapter 7 : Conservation of Plants and Animals >>

Science - NCERT Solution - Science : CBSE NCERT Exercise Solutions for Class 8th for Combustion and Flame will be available online in PDF book form soon. The solutions are absolutely Free. Soon you will be able to download the solutions.

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