Page 39 - Genius Kidz Prudence Learning Sc-8

(a) Combustible substance : A substance that produced. And this type of combustion is
can burn in presence of air or oxygen is called complete combustion, for example,
known as combustible substance.
CH + 2O ¾¾® CO + 2H O + Energy
(b) Air or Oxygen : In the absence of oxygen, 4 2 2 2
combustion is not supported as it is often (Methane) (Oxygen) (Carbon (Water)
Dioxide)
seen in the case of fire that we try to cut the
oxygen supply to stop it. If the amount of oxygen available is insufficient
then the products obtained include carbon
monoxide, water and energy. And this type of

combustion is called incomplete combustion.

CH + O ¾¾® (CO) + (H O) + Energy
4 2 2
(Methane) (Oxygen) (Carbon (Water)
Monooxide)

Combustion in absence of fire
Unburnt carbon particles are released as
In the above picture, blanket is used so that
“soot” during combustion.
oxygen or air supply can be cut off and thus fire
Types of Combustion
is extinguished.
(a) Rapid combustion :
(c) Ignition temperature : The minimum
temperature required for a substance to (i) It takes place at a very fast speed.
cath fire under normal atmospheric (ii) It is accompanied by the release of large
conditions is called ignition temperature of amount of heat and light energy.
the substance. (iii) It results in fire usually.

Substances with low ignition temperature (iv) It is used in exploding crackers and in
are called inflammable substances, for burning a stove.
example, petrol, ether, paper, benzene, etc.
(b) Slow combustion :
Substances with high ignition temperature (i) It takes place at a slow speed.
need to be heated first for their burning

because their ignition temperature is (ii) It is accompanied by the release of
attained by heating, for example, burning very little amount of heat and light
of a log of wood or wick of a candle. energy or light energy is not even
released.
Products of Combustion
(iii) Examples of slow combustion include
If the amount of oxygen available is sufficient
oxidation of food or cellular respiration.
then carbon dioxide, water and energy are

2H (Hydrogen) + (O ) (Oxygen) ® 2(H O) (Water) + Energy.
2
2
2
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