This PPT was made as part of a school Project... Excuse me.

1. COMBUSTION AND FOSSIL
FUELS
OUR OWN HIGH SCHOOL, AL WARQA’A,
DUBAI

2. COMBUSTION
• The process of burning of a substance in the presence of air
or oxygen with the liberation of heat and light is called
combustion.
• Combustion is also the scientific name for burning.
• Substances that burn in air or oxygen to produce heat and
light are called combustible substances.
Example: Paper, wood, kerosene and LPG.
• Substances that do not burn in air or oxygen to produce heat
and light are called non-combustible substances.
Example: Water, sand, glass and cement.

3. TYPES OF COMBUSTION
• Rapid Combustion – In this combustion, a large amount of heat and
light are released in a very short span of time.
Example: Combustion of LPG.
• Explosion – This type of combustion is characterized by the sudden
release of heat, light and sound accompanied by the liberation of a
large amount of gas.
Example: Bursting of firecrackers.
• Spontaneous combustion – Here, substances catch fire on their own
without the application of heat.
Example: Phosphorus catches fire in room temperature.

4. CONDITIONS NECESSARY FOR
COMBUSTION
• Presence of a combustible substance – Combustion is
only possible with a combustible substance.
• Presence of a supporter of combustion – Adequate
supply of a supporter of combustion like oxygen is
essential.
• Attainment of ignition temperature
 The temperature at which a particular substance burns
in the presence of air is called its ignition
temperature.
 A substance cannot catch fire if its temperature is lower
than its ignition temperature.
 Substances like alcohol, petrol, LPG and synthetic

5. EXTINGUISHING A FIRE
• Fire can be extinguished using water. Water evaporates,
taking away heat from the fire while cooling down the burning
material below its ignition temperature.
• Water should not be poured over burning petrol, diesel or
kerosene because they are lighter than water and do not mix
with it. So water just forms a layer beneath them and the
substance continues to burn.
• Water conducts electricity, so it should not be used over
electrical fires. It can pose danger to the people who are trying
to extinguish it.

6. TYPES OF FIRE EXTINGUISHER
• Most fire extinguishers use CO2 (Carbon Dioxide) as it is not
a supporter of combustion. As it is heavier than air, CO2
settles down and cuts off the oxygen supply and therefore,
extinguishes the fire.
• There are commonly two types of fire extinguishers:
• Carbon dioxide fire extinguisher – This type of fire
extinguisher consists of carbon dioxide filled under high
pressure in cylinders.
• Soda-acid fire extinguisher – It has a concentrated
solution of sodium hydrogen carbonate and sulphuric acid
in separate compartments. When the extinguisher is used,
the two substances come in contact with each other and

7. FLAME
• Flame is a region where combustion of fuel takes place.
• The colour of flame depends upon the temperature, amount of
air available and the nature of the burning substance.
• Hydrocarbons burn with blue or yellow flame.
• A yellow flame is also called a luminous flame because it
emits a lot of light. It’s mostly seen when there is in-sufficient
oxygen. Its temperature is lower than that of a blue flame. It
leaves behind black soot and other residue.
• A blue flame is also called a non-luminous flame as it emits
less light. It’s observed when there is adequate amount of
oxygen. It doesn’t leave behind and residue.

8. COMBUSTION OF A WAX
CANDLE
If you ever observe the candle flame closely, this is what you
see :
• The wick burns and stands in a pool of liquid wax.
• There is a small portion of unburnt wick between the flame
and the liquid wax.
• The liquid wax is trapped in a ‘cup’ of solid wax.
• Both liquid and solid wax never catch fire.
The wick is not the only substance burning because the candle
gets smaller too. So in addition to the wick, the wax vapours
also burn to form the flame.

9. ZONES OF A CANDLE FLAME
Middle zone
(Yellow) – It’s
less hot than the
outer zone.
Incomplete
combustion of
wax vapours
produces CO2
and Carbon
monoxide. This
zone emits most
light
Outer zone (blue) –
Hottest part of the
flame. Wax vapours
have enough oxygen
for complete
combustion
(producing CO2 and
H2O. This zone emits
very less light.
Inner zone
(Black) –
Coolest part of
the flame. Wax
vapours remain
un-burned as
no oxygen is
available. It’s
completely dark
and emits no
light.

10. FUELS
• Substances that produce heat and light energy on burning
are called fuels.
Examples: Wood, coal, cow dung cakes, kerosene,
LPG, petrol.
• Fuels are used for cooking, heating, in automobiles and for
generating electricity.
• Based on the physical state of fuels, they can be classified
into three:
SOLID FUELS LIQUID FUELS GASEOUS FUELS
Fuels that exist in
solid state at room
temperature are solid
fuels.
Example: Charcoal,
wood, coal.
Fuels existing in liquid
state at room
temperature are liquid
fuels.
Example: Petrol,
diesel, fuel oil.
Fuels that exist in
gaseous state at room
temperature are
gaseous fuels.
Example:
Petroleum gas,
natural gas, biogas.

11. CHARACTERISTICS OF FUELS
• The most two important characteristics are its calorific
value and efficiency.
• Calorific value of a fuel is defined as the amount of
heat produced in kilojoules when one gram of a fuel is
completely burned.
• The unit for representing calorific value is kilojoule (kJ).
The value is expressed in kJ/g.
• If the calorific value of fuel is higher, it produces more
heat while burning.

12. CALORIFIC VALUE OF SOME
FUELS
FUEL
Calorific
Value
(kJ/g)
FUEL
Calorific
Value
(kJ/g)
Wood Pellets 17 Petrol 47
Coal 25 - 33 Biogas 35 - 40
Charcoal 35 LPG 50
Cow Dung
Cakes
7 Methane 55
Coke 33 Hydrogen 150
Kerosene 48 Diesel 45

13. SOME IMPORTANT
CHARACTERISTICS
• An Ideal fuel should have a high calorific value.
• Its ignition temperature should be low but above room
temperature.
• It should have a moderate rate of combustion and should
release heat in a controlled manner.
• Must be available easily and fairly cheap.
• Must be safe to handle, store and transport.
• It should not cause pollution during burning.

14. FEW OF THE COMMON FUELS
• Hydrogen – Hydrogen is considered as the best fuel as it has
the highest calorific value. But it is highly inflammable. There
are also few difficulties associated with transport, storage etc.
Example : Rocket Fuel
• Methane and LPG – They have fairly high calorific values.
They burn with smokeless fire and, therefore they don’t cause
pollution. They are also easily stored and transported through
cylinders and pipelines.
Example : Cooking
• Petrol and Diesel – Mostly used in automobiles. The main
disadvantage is the limited availability and that their
combustion releases a lot of Carbon Monoxide (CO), Volatile
Organic Compounds (VOC’s) and Nitrogen Oxides (NOX)

15. FOSSIL FUELS
• Fossil Fuels are formed from the buried remains if of
plants and animals over a period of millions of years.
Examples : Coal, Petroleum and Natural Gas
• They are also referred to as natural resources. They can
be of two types.
• Inexhaustible – Resources which have unlimited
supply.
Examples : Sunlight, Air
• Exhaustible – Resources which have limited supply.
Examples : Fossil Fuels, Forests and wildlife

16. COAL
• Coal is generally black or brownish-black un color.
• Depending on its carbon content, it can be divided into
three types :
• Anthracite – It has a carbon content of around 86% or
higher and is regarded as the best grade of coal. Its
mainly used for heating.
• Bituminous Coal – It has a carbon content of around
70-80% and is mainly used for power generation and
for manufacturing another fuel called Coke.
• Lignite – It has a carbon content of around 60-70%
and is regarded as the lowest grade of coal. It’s mainly
used for power generation.

17. FORMATION OF COAL
• Trees and other plants that grew in swampy
areas 300-400 Million years ago died and their
remains got buried in the swampy soil. Over
time, the remains got covered with layers of
sediments like mud and sand.
• In low-oxygen conditions, the buried plant
material formed a dark brown material called
peat.
• Gradually more and more sediments got
deposited over peat. Peat was compressed
between layers of sediments and formed
lignite.
• Further compression resulted in the formation
of bituminous coal.
• Even further compression resulted in the

18. PETROLEUM REFINING
• Petroleum Gas – Used as a domestic fuel in liquefied form,
LPG.
• Petrol – Used as a fuel in automobiles, dry cleaning etc.
• Kerosene – Used as fuel in lamps, stoves and also used as
jet fuel.
• Diesel – Used as a fuel in heavy motor vehicles and
generators.
• Fuel Oil – For power stations and ships.
• Lubricating Oil – Used for lubrication, paraffin wax (used in
candles, ointments, Vaseline etc.) and asphalt (used for
making roads.

20. ANSWER THE FOLLOWING
• What are the three essential conditions necessary for
combustion?
• Explain how CO2 extinguisher is able to control fires.
• Can the process of rusting be called combustion? Give reason.
• Charcoal does not burn with flame, but glows. Why?
• Why is hydrogen not used as a domestic fuel even though it has
calorific value?
• A flame always points upwards. Why?
• ‘Burning petrol produces nitrogen oxides and water’. Is this
statement right or wrong? Justify your answer.