COMBUSTION AND FLAME
DELHI PUBLIC SCHOOL,RANIPUR,HARIDWAR
LESSON 6:COMBUSTION AND FLAME
DATED:24.07.14
1
COMBUSTION:
When a substance combines readily with oxygen to give heat and (light) it is called combustion.
2
COMBUSTILE SUBSTANCE:
A substance which burns easily to give heat it is said to be combustible. For ex. Wood ,paper
3
FUEL:
A substance that is burnt for obtaining heat and light is called a fuel.
Carbon based fuel: wood ,coal,wax ,petrol etc.
Non carbon based fuel: hydrogen
4
CHARACTERISTICS OF AN IDEAL FUEL:
An ideal fuel should :
i)Have high calorific value ii)Have moderate ignition temperature iii)Be easy to store and handle iv)Burn completely leaving no solid residues or smoke i.e should be pollution free.
v)Be cheap and easily available. vi)Have moderate rate of combustion
5
CALORIFIC VALUE:
The amount of heat energy released on complete combustion of 1 kg of a fuel in air or oxygen is called its calorific value. It is expressed in kJ/kg.
Hydrogen has the highest calorificvalue :150000 KJ/Kg.
* Table of calorific value of different fuels is given on pg 73 of the NCERT book.
6
CONDITIONS NECESSARY FOR COMBUSTION:
a)Presence of oxygen or air
b)Presence of combustible substance
c)Correct ignition temperature
7
TYPES OF COMBUSTION:
6
SPONTANEOUS COMBUSTION :
When a substance suddenly bursts into flame at room temperature, without application of a cause(heat), it is called spontaneous combustion .
Ex burning of phosphorus, sodium in air,forest fires
7
RAPID COMBUSTION:
When a substance burns rapidly ,on application of heat and produces heat and light it is rapid combustion. Ex burning of petrol, LPG
8
SLOW COMBUSTION:
When a substance burns in oxygen slowly without applying heat, to give out small amount of heat but no light, it is called slow combustion .Ex burning of food in our body, rusting of iron
9
EXPLOSION:
A sudden reaction takes place with the evolution heat,lightand sound.A large amount of as is alson liberated.Such a
LESSON 6:COMBUSTION AND FLAME
DATED:24.07.14
1
COMBUSTION:
When a substance combines readily with oxygen to give heat and (light) it is called combustion.
2
COMBUSTILE SUBSTANCE:
A substance which burns easily to give heat it is said to be combustible. For ex. Wood ,paper
3
FUEL:
A substance that is burnt for obtaining heat and light is called a fuel.
Carbon based fuel: wood ,coal,wax ,petrol etc.
Non carbon based fuel: hydrogen
4
CHARACTERISTICS OF AN IDEAL FUEL:
An ideal fuel should :
i)Have high calorific value ii)Have moderate ignition temperature iii)Be easy to store and handle iv)Burn completely leaving no solid residues or smoke i.e should be pollution free.
v)Be cheap and easily available. vi)Have moderate rate of combustion
5
CALORIFIC VALUE:
The amount of heat energy released on complete combustion of 1 kg of a fuel in air or oxygen is called its calorific value. It is expressed in kJ/kg.
Hydrogen has the highest calorificvalue :150000 KJ/Kg.
* Table of calorific value of different fuels is given on pg 73 of the NCERT book.
6
CONDITIONS NECESSARY FOR COMBUSTION:
a)Presence of oxygen or air
b)Presence of combustible substance
c)Correct ignition temperature
7
TYPES OF COMBUSTION:
6
SPONTANEOUS COMBUSTION :
When a substance suddenly bursts into flame at room temperature, without application of a cause(heat), it is called spontaneous combustion .
Ex burning of phosphorus, sodium in air,forest fires
7
RAPID COMBUSTION:
When a substance burns rapidly ,on application of heat and produces heat and light it is rapid combustion. Ex burning of petrol, LPG
8
SLOW COMBUSTION:
When a substance burns in oxygen slowly without applying heat, to give out small amount of heat but no light, it is called slow combustion .Ex burning of food in our body, rusting of iron
9
EXPLOSION:
A sudden reaction takes place with the evolution heat,lightand sound.A large amount of as is alson liberated.Such a