NCERT Book : Combustion & flame Class 8 Notes | EduRev

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Class 8 : NCERT Book : Combustion & flame Class 8 Notes | EduRev

 Page 1


BAL BHARATI PUBLIC SCHOOL, PITAMPURA, DELHI-110034        
 
CLASS-8  Term II (2013-2014) 
Chemistry Notes 
 
COMBUSTION AND FLAME     
 
Q1:Define combustion. 
Ans1: Combustion is the process of burning of a substance in the presence of air or oxygen 
with the liberation of energy in the form of heat and light. 
 
Q2: List the conditions necessary for combustion. 
Ans2: The conditions necessary for combustion are:  
(1) Presence of combustible substance 
(2) Supporter of combustion  
(3) Attainment of ignition temperature 
 
Q3: Differentiate between combustible & non-combustible substances. 
Ans3: Those substances which burn easily are called combustible substances. for eg.  
Paper, petrol, LPG & wood etc. 
Substances which do not burn in air or oxygen are called non-combustible substances. For 
eg. glass, sand, soil & cement. 
 
Q4: What is an inflammable substance? 
Ans4: The substances having very low ignition temperature catch fire easily.such 
substances are called inflammable substances. For eg. Petrol,CNG,LPG,alcohol. 
 
Q5: Name the different types of combustion. 
Ans 5: Combustion is mainly of three types:  
1.Rapid combustion 
2.Spontaneous combustion 
3. Explosion 
 
Q6: Differentiate between different types of combustion. 
Page 2


BAL BHARATI PUBLIC SCHOOL, PITAMPURA, DELHI-110034        
 
CLASS-8  Term II (2013-2014) 
Chemistry Notes 
 
COMBUSTION AND FLAME     
 
Q1:Define combustion. 
Ans1: Combustion is the process of burning of a substance in the presence of air or oxygen 
with the liberation of energy in the form of heat and light. 
 
Q2: List the conditions necessary for combustion. 
Ans2: The conditions necessary for combustion are:  
(1) Presence of combustible substance 
(2) Supporter of combustion  
(3) Attainment of ignition temperature 
 
Q3: Differentiate between combustible & non-combustible substances. 
Ans3: Those substances which burn easily are called combustible substances. for eg.  
Paper, petrol, LPG & wood etc. 
Substances which do not burn in air or oxygen are called non-combustible substances. For 
eg. glass, sand, soil & cement. 
 
Q4: What is an inflammable substance? 
Ans4: The substances having very low ignition temperature catch fire easily.such 
substances are called inflammable substances. For eg. Petrol,CNG,LPG,alcohol. 
 
Q5: Name the different types of combustion. 
Ans 5: Combustion is mainly of three types:  
1.Rapid combustion 
2.Spontaneous combustion 
3. Explosion 
 
Q6: Differentiate between different types of combustion. 
If a combustion reaction takes place with a high speed &in which a large amount of heat & 
light are produced in a short time is called Rapid combustion. for eg. burning of matchstick, 
burning of magnesium ribbon. 
A combustion which occurs on its own ,without the application of heat is called spontaneous 
combustion. For eg. Forest fire, burning of white phosphorus. 
The process of combustion where large amount of gases are evolved with the production of 
a tremendous amount of heat, light and sound is called explosion. for eg. Burning of 
crackers. 
 
Q7: What is an incomplete combustion ?  
Ans7: Incomplete combustion of a substance takes place in the presence of insufficient 
amount of air or oxygen, this results in the formation of carbon monoxide, soot, heat &light. 
 
Q8: Which device is used to extinguish fire &state the principle of extinguishing fire? 
Ans8: Fire extinguisher is used to extinguish fire. Fire may be extinguished  
1.By removing all the combustible substances. 
2. By cutting off the supply of air (supporter of combustion). 
3.By cooling the burning substances below their ignition temperature. 
 
Q9: What are the characteristics of an ideal fuel ? 
Ans 9  An ideal fuel should have the following characteristics: 
1.It should have a high calorific value. 
2. It should not produce any harmful products on burning. 
3. It should cause minimum pollution of air. 
4. It should be cheap and readily available. 
5. It should be easy to store,transport and handle. 
6. Its ignition temperature should be above the room temperature. 
7. It should leave no residue after burning. 
8. It should burn at a moderate rate. 
 
Q10: Define Calorific value of a fuel . 
Ans 10: The amount of heat produced on complete combustion of one kg of a fuel is known 
as its calorific value.it is usually expressed in joule per kg (kj/kg).  
 
Page 3


BAL BHARATI PUBLIC SCHOOL, PITAMPURA, DELHI-110034        
 
CLASS-8  Term II (2013-2014) 
Chemistry Notes 
 
COMBUSTION AND FLAME     
 
Q1:Define combustion. 
Ans1: Combustion is the process of burning of a substance in the presence of air or oxygen 
with the liberation of energy in the form of heat and light. 
 
Q2: List the conditions necessary for combustion. 
Ans2: The conditions necessary for combustion are:  
(1) Presence of combustible substance 
(2) Supporter of combustion  
(3) Attainment of ignition temperature 
 
Q3: Differentiate between combustible & non-combustible substances. 
Ans3: Those substances which burn easily are called combustible substances. for eg.  
Paper, petrol, LPG & wood etc. 
Substances which do not burn in air or oxygen are called non-combustible substances. For 
eg. glass, sand, soil & cement. 
 
Q4: What is an inflammable substance? 
Ans4: The substances having very low ignition temperature catch fire easily.such 
substances are called inflammable substances. For eg. Petrol,CNG,LPG,alcohol. 
 
Q5: Name the different types of combustion. 
Ans 5: Combustion is mainly of three types:  
1.Rapid combustion 
2.Spontaneous combustion 
3. Explosion 
 
Q6: Differentiate between different types of combustion. 
If a combustion reaction takes place with a high speed &in which a large amount of heat & 
light are produced in a short time is called Rapid combustion. for eg. burning of matchstick, 
burning of magnesium ribbon. 
A combustion which occurs on its own ,without the application of heat is called spontaneous 
combustion. For eg. Forest fire, burning of white phosphorus. 
The process of combustion where large amount of gases are evolved with the production of 
a tremendous amount of heat, light and sound is called explosion. for eg. Burning of 
crackers. 
 
Q7: What is an incomplete combustion ?  
Ans7: Incomplete combustion of a substance takes place in the presence of insufficient 
amount of air or oxygen, this results in the formation of carbon monoxide, soot, heat &light. 
 
Q8: Which device is used to extinguish fire &state the principle of extinguishing fire? 
Ans8: Fire extinguisher is used to extinguish fire. Fire may be extinguished  
1.By removing all the combustible substances. 
2. By cutting off the supply of air (supporter of combustion). 
3.By cooling the burning substances below their ignition temperature. 
 
Q9: What are the characteristics of an ideal fuel ? 
Ans 9  An ideal fuel should have the following characteristics: 
1.It should have a high calorific value. 
2. It should not produce any harmful products on burning. 
3. It should cause minimum pollution of air. 
4. It should be cheap and readily available. 
5. It should be easy to store,transport and handle. 
6. Its ignition temperature should be above the room temperature. 
7. It should leave no residue after burning. 
8. It should burn at a moderate rate. 
 
Q10: Define Calorific value of a fuel . 
Ans 10: The amount of heat produced on complete combustion of one kg of a fuel is known 
as its calorific value.it is usually expressed in joule per kg (kj/kg).  
 
Q11: Define ignition temperature ? 
Ans 11: The lowest temperature at which a substance catches fire and starts burning is 
known as ignition temperature. 
 
Q12: How is a flame produced?  
Ans 12: A flame is said to be produced when a combustible substance is in the vapour state 
& burns. 
 
Q13: Name the zones of a candle flame along with a labelled diagram. 
Ans13: A candle flame consists of three zones  
1.Non-luminous zone or zone of complete combustion. 
2.Luminous zone or zone of incomplete combustion. 
3. Dark zone or zone of no combustion. 
Refer to N.C.E.R.T for the diagram. 
 
Q14: What is Green house effect ? explain its consequence. 
Ans 14:An increase in the concentration of carbon dioxide in the atmosphere leads to an 
increase in the temperature of the earth is called GREENHOUSE EFFECT. 
Its consequences are melting of polar ice ,raising the level of water in seas and oceans.This 
would cause flooding and submerging of many low lying areas. 
 
Q15: Define Acid rain .Explain its consequences. 
Ans 15: Burning of coal and diesel releases sulphur dioxide gas &oxides of nitrogen which 
when dissolved in rainwater produces the acid rain.It is quite harmful for crops,buildings and 
soil. These gases also cause respiratory problems like asthma and bronchitis. 
***** 
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