Chemistry PPT

1. WELCOME TO SCIENCE
CHEMISTRY
GROUP PRESENTATION

2. TOPIC-
COMBUSTION

3. COMBUSTION
The process of burning of substance in air with the release
of heat and light is known as combustion.
Combustible substance: A substance that burns in the air to
produce heat and light is called a combustible substance.
For example: Wood, paper, kerosene and LPG.
Combustible substance: A substance that does not burn in
air is called a non-combustible substance.
For example: Stone, metal and plastic.

4.  Combustionis a chemicalchange.Duringcombustionsubstanceslikecoalorcharcoal
reactwithoxygenin theairtoformcarbondioxideandwater.
* C + O2 = CO2 + Heat
Carbon + Oxygen =Carbondioxide
Hydrogenreactswithoxygentoformwater.
* 2H2 + O2 =2H2O +Heat
Hydrogen +Oxygen =Water
Naturalgasandbiogascontainmethane,whichburnstoproducecarbondioxideand
water.
*CH4 +2O2 =CO2 +2H2O +Heat
Methane +Oxygen =Carbondioxide +Water

5. CONDITIONS NECESSARY FOR COMBUSTION
*In the presence of a combustible substance.
*In the presence of oxygen[air].
*On attainment of ignition temperature.
If any of these conditions is not met, combustion does not
take place.

6. IGNITION TEMPERATURE
The ignition temperature at which a substance
catches fire is called its ignition temperature.
Substances like petrol , kerosene , alcohol and LPG
have low ignition temperatures and can easily catch
fire. They are called inflammable substances.

7. TYPES OF COMBUSTION-
 Rapidcombustionoccurswhenasubstanceburnsrapidlytoproduceheatand
lightasinLPG, paperandthewickofanoillamp.
 Spontaneouscombustionoccurswhena substance startsburningsuddenlyeven
withoutbeingheated.
 Explosionisa combustionreactionthatoccurssuddenly whena materialis
heated, liberatinga largeamountofheat, lightandsound. Firecrackersarethe
bestexamplesofexplosion.

8. EXTINGUISHING A FIRE
* Toextinguisha fire:
• Removethecombustiblematerial.
• Reducetemperatureto belowtheignitiontemperatureof the
combustiblesubstance.
• Cutoffairsupply

9. FIRE EXTINGUISHERS:
Dry powder fire
extinguisher.
Soda-acid fire
extinguisher.
Foam fire