COMBUSTION AND FLAME

● The chemical process in which a substance reacts with oxygen to produce heat is called combustion. Combustion ● Substance which undergoes combustion is combustible substance.

Eg :- Wood Coal LPG Kerosene. Combustible substances Substances which burn in air to produce heat and light

Conditions for Combustion Substance will not burn without these conditions: Fuel Air (to supply oxygen) Heat (to raise the temperature beyond the ignition temperature)

Types of combustion Rapid combustion Three main types of combustion : E.g.:- burning of LPG

Spontaneous combustion phosphorus burns spontaneously at room temperature

Explosion E.g. crackers

We should install a fire extinguish in :- ●Offices ●Big buildings ●Commercials place ●Public places How do we control fire ?

●Call fire brigade to control fire first ● use sand or water to control fire Note:- do not use water on electric fire

i) Solid fuels :- Eg:- wood, coal, charcoal etc. Types of fuels :-

E.g:- kerosene, petrol, diesel etc. ii) Liquid fuels :-

Eg:- CNG, LPG, biogas, hydrogen etc iii) Gaseous fuels :-

vi) Does not cause pollution Characteristics of a good fuel :- i) readily available. ii) cheap. iii) easy to store and transport. iv) Burns at a moderate rate. v) Produces a large amount of heat.

Structure of a candle flame or burning :- Flame :- Outer zone (blue) Middle zone (yellow) Inner zone (black) (Complete combustion) (Partial combustion) Hottest part Least hot Luminous zone Non luminous zone

Flame :- Substances which vaporizes during burning produce flames E.g.:- kerosene wax

Substances which do not vaporizes during burning do not produce flames. E.g.:- Coal Charcoal

Assessment Fill in the blanks: – a) Burning of wood and coal causes ______ of air. b) A liquid fuel, used in home is _______. c) Fuel must be heated to its ________ before it starts burning. d) Fire produced by oil can not be controlled by _________.