2. Acknowledgement
Information and pictorial illustrations to create this
work have been drawn from class notes, prescribed
text books and various internet resources. The
author gratefully acknowledges the same. Any
objections to the use of internet resources may
please be indicated to suddurocks@yahoo.in so
that the same can be removed from the illustrations
used in this file.
This presentation is created with the sole intention
of benefitting a large number of student
community. This may not be used for any
commercial purpose.
3. Contents:
Combustion
Ignition Temperature
Inflammable Substances
Controlling Fire
Types of Combustion
Explosion
Fuel Efficiency
Burning of Fuels Leads to Harmful
Products
4. Combustion
A chemical process in which a substance
reacts with oxygen to give off heat is called
Combustion.
The substance that undergoes combustion is
said to be combustible. It is also called a
Fuel.
The fuel may be solid, liquid or gas.
Sometimes, light is also given off during
combustion, either as a flame or as a glow.
5. Ignition Temperature
When the cloths of a person catch fire, the
person is covered with a blanket to
extinguish fire.
The lowest temperature at which a
substance catches fire is called its
Ignition Temperature.
6. Inflammable Substances
The substances which have a very low Ignition
temperature and can easily catch fire with a
flame are called Inflammable Substances.
Example : Petrol, alcohol, Liquified Petroleum
Gas (LPG),…Etc.
7. Controlling Fire
• When a fire bridge arrives, it pours water on the
fire. Water cools the combustible material so
that its temperature is brought below its Ignition
Temperature.
• This prevents the fire from spreading. Water
vapours also surround the combustible material,
helping in cutting off the supply of air.
• So, the fire is extinguished.
8. • We must never use water to put out an oil fire
because oil floats on water and the fire would
spread more.
• We must never use water to put out an Electric
fire because the person spraying water can
receive an electric shock.
9. Types of Combustion
When we bring a burning match stick or a gas
lighter near the gas stove in the kitchen and
turn on the knob, the gas burns rapidly and
produces heat and light.
Such combustion is known as Rapid
Combustion.
The type of combustion in which a material
suddenly bursts into flames, without the
application of any apparent cause is called
Spontaneous Combustion.
10. Explosion
When a cracker is ignited, a sudden reaction
takes place with the evolution of heat, light and
sound.
A large amount of gas found in the reaction is
liberated.
Such a reaction is called an Explosion.
Explosion can also take place if pressure is
applied on the cracker.
11. Fuel Efficiency
► The amount of heat energy produced on a
complete combustion of 1kg of a fuel is
called its Calorific Value.
► The value of a fuel is expressed in a unit
called Kilojoules per Kg.
12. Burning of Fuels Leads to
Harmful Products
Carbon fuels like wood, coal, petroleum
release unburnt carbon particles. These
fine particles are dangerous pollutants
causing respiratory diseases like Asthma.
Incomplete combustion of these fuels
gives carbon monoxide gas. It is a very
poisonous gas. It is dangerous to burn
coal in a closed room. This gas produced
can kill persons sleeping in that room.
13. Combustion of most fuels releases carbon
dioxide in the environment. Increased
concentration of carbon dioxide in the air
is believed to cause Global Warming.
Global warming is the raise in temperature
of the atmosphere for the earth. This
results, among other things, in the melting
of polar glaciers, which leads to a raise in
the sea level causing floods in the costal
areas. Low lying costal areas may even be
permanently submerged in water.
