Combustion & Flame Class 8 PPT

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CHAPTER - 6 
 
COMBUSTION AND FLAME 
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CHAPTER - 6 
 
COMBUSTION AND FLAME 
1) Combustible substances :- 
   Substances which burn in air to produce heat and 
light are called combustible substances. 
 Eg :- wood, coal, charcoal, kerosene, petrol, 
diesel, liquified petroleum gas (LPG), compressed 
natural gas (CNG) etc. 
    Wood                Coal                    LPG               Kerosene 
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CHAPTER - 6 
 
COMBUSTION AND FLAME 
1) Combustible substances :- 
   Substances which burn in air to produce heat and 
light are called combustible substances. 
 Eg :- wood, coal, charcoal, kerosene, petrol, 
diesel, liquified petroleum gas (LPG), compressed 
natural gas (CNG) etc. 
    Wood                Coal                    LPG               Kerosene 
2) Combustion :- 
    The chemical process in which a substance reacts with 
oxygen to produce heat is called combustion. 
    The substance which undergoes combustion is called a 
combustible substance. It is also called a fuel. 
    Sometimes light is also produced during combustion 
either as a flame or as a glow. 
    Air is necessary for combustion. 
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CHAPTER - 6 
 
COMBUSTION AND FLAME 
1) Combustible substances :- 
   Substances which burn in air to produce heat and 
light are called combustible substances. 
 Eg :- wood, coal, charcoal, kerosene, petrol, 
diesel, liquified petroleum gas (LPG), compressed 
natural gas (CNG) etc. 
    Wood                Coal                    LPG               Kerosene 
2) Combustion :- 
    The chemical process in which a substance reacts with 
oxygen to produce heat is called combustion. 
    The substance which undergoes combustion is called a 
combustible substance. It is also called a fuel. 
    Sometimes light is also produced during combustion 
either as a flame or as a glow. 
    Air is necessary for combustion. 
3) Air is necessary for burning :-  
 
 
 
 
 
 
 
 
 
 
   
                           (a)                                           (b)                                         (c) 
     Fix a lighted candle on a table. Put a glass chimney over the table and rest 
it on a few wooden blocks in such a way so that air can enter the chimney. 
Observe what happens to the flame. 
     Now remove the blocks and let the chimney rest on the table. Again 
observe the flame. 
     Then put a glass plate over the chimney. Observe the flame again. 
     The candle burns freely in (a) because air enters the chimney from below. 
     The candle stops burning in (b) because air does not enter the chimney 
from below. 
     The candle does not burn in (c) because air is not available. 
  This shows that air is necessary for burning. 
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CHAPTER - 6 
 
COMBUSTION AND FLAME 
1) Combustible substances :- 
   Substances which burn in air to produce heat and 
light are called combustible substances. 
 Eg :- wood, coal, charcoal, kerosene, petrol, 
diesel, liquified petroleum gas (LPG), compressed 
natural gas (CNG) etc. 
    Wood                Coal                    LPG               Kerosene 
2) Combustion :- 
    The chemical process in which a substance reacts with 
oxygen to produce heat is called combustion. 
    The substance which undergoes combustion is called a 
combustible substance. It is also called a fuel. 
    Sometimes light is also produced during combustion 
either as a flame or as a glow. 
    Air is necessary for combustion. 
3) Air is necessary for burning :-  
 
 
 
 
 
 
 
 
 
 
   
                           (a)                                           (b)                                         (c) 
     Fix a lighted candle on a table. Put a glass chimney over the table and rest 
it on a few wooden blocks in such a way so that air can enter the chimney. 
Observe what happens to the flame. 
     Now remove the blocks and let the chimney rest on the table. Again 
observe the flame. 
     Then put a glass plate over the chimney. Observe the flame again. 
     The candle burns freely in (a) because air enters the chimney from below. 
     The candle stops burning in (b) because air does not enter the chimney 
from below. 
     The candle does not burn in (c) because air is not available. 
  This shows that air is necessary for burning. 
4) Ignition temperature :- 
   The minimum temperature at which a substance catches fire and 
burns is called its ignition temperature. 
    A substance will not catch fire and burn if its temperature is lower 
than its ignition temperature. 
   Different substances have different ignition temperatures. 
   Eg:- The ignition temperature of kerosene is less than the ignition 
temperature of wood. 
   Substances which have very low ignition temperature and can easily 
catch fire with a flame are called inflammable substances. Eg:- petrol, 
alcohol, LPG, CNG etc.