The chemical process of burning of a substance in presence of oxygen to produce heat is called as Combustion.
The substance that is burned is called as Fuel OR Combustible substance.
Air is the source of oxygen for combustion
The substance needs fire (source of heat) to burn.
TYPES OF COMBUSTION:
Rapid Combustion: The burning of substance in which large amount of heat is produced in a short time is called as Rapid Combustion.
Spontaneous Combustion: When burning of a substance do not require any external source for ignition/burning this is called as Spontaneous Combustion. Example: Forest Fire, Sodium metal
Explosive Combustion: When a excessive release of energy or large amount of gas is formed this is called as Explosive Combustion. Example: Crackers.
Combustion can be classified as Complete and Incomplete:
When sufficient amount of oxygen is available for the fuel to burn this is called as Complete Combustion.
When amount of oxygen is limited in air the carbon in substance do not burn completely and produces soot this is called as Incomplete combustion.
How Do We Control Fire?
Fire is the source of heat.
There are three essential requirements for producing fire:
These are: fuel, air (to supply oxygen) and heat (to raise the temperature of the fuel beyond the ignition temperature).
Fire can be controlled by removing one or more of these requirements.
IGNITION TEMPERATURE:
The lowest temperature at which a substance catch fire is called as Ignition Temperature.
Ignition temperature is different for different substance.
It can be lowered.
The Ignition Temperature of kerosene oil is lower than wood thats why kerosene oil catches fire easily.
What are Inflammable substance?
The substances which have very low ignition temperature and can easily catch fire with a flame are called inflammable substances.
Examples of inflammable substances are petrol, alcohol, Liquified Petroleum Gas (LPG)
FLAME: Its parts and formation
Flame is the region where combustion of fuel takes place. Flame is formed when a substance vaporized on heating
In candle the wax first melt and then vapourise, the vapours rise upward and burns into flame.
A flame has three main zones:
Non-Luminous zone: It is the outermost zone of complete combustion. Flame is blue in colour.
Luminous zone: It is the middle zone of incomplete combustion (due to less air) Flame is orange in colour.
Dark Zone: It is innermost zone or zone of no combustion. It is the coolest part of flame.
Goldsmiths blow the outermost zone of a flame with a metallic blowpipe for melting gold and silver because the outermost zone is the hottest part of flame used for designing.
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