The document explains combustion as a chemical process involving the burning of a substance in the presence of oxygen, producing heat and light. It outlines types of substances (combustible and non-combustible), conditions required for combustion, ignition temperatures, and methods to control fire. Additionally, it differentiates between various combustion types, including rapid combustion, spontaneous combustion, and explosions, and describes the structure of flames.

1. COMBUSTION AND FLAME
CLASS 8, CHEMISTRY
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NOTE- ALL THE ACTIVITIES ARE
GIVEN TOWARDS THE END OF THE
CHAPTER.

2. EXCLUDED CONTENTS-
• ALL THE ACTIVITIES IN NCERT
• BURNING OF FUELS LEADS TO HARMFUL
PRODUCTS
• IF ANY OTHER THING IS LEFT OUT, IT WILL BE
COVERED IN THE SECOND PART

3. WHAT IS COMBUSTION EXACTLY?
• Combustion in a chemical process in
which a substance reacts (burns) in the
presence of oxygen in order to give off
heat and light. Light is produced either in
form of flame or in form of glow.
• The substance which burns is often
referred to as a fuel or a combustible
substance. PPT BY @RIDHIMAWAHI

4. EXAMPLES OF COMBUSTION
• Magnesium + O2 à MgO ( magnesium oxide) +
heat + light
• Carbon + O2 à carbon dioxide + heat + light
FOOD- A FUEL FOR OUR BODIES
When food reacts with oxygen ( undergoes
respiration, a lot of energy is produced. Similarly,
when any other combustible substance undergoes
combustion, energy is released.
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5. COMBUSTIBLE AND NON-
COMBUSTIBLE SUBSTANCES
COMBUSTIBLE
• They are the substances
which burn in the presence
of oxygen in order to give
off heat and light.
• In other words, these are
the substances that
undergo combustion.
• Ex- magnesium, wood, lpg,
coal, petroleum.
NON- COMBUSTIBLE
• While on the other hand,
these are the substances
that do not react ( burn)
with oxygen.
• As a result, they do not
undergo combustion.
• Examples- plastic, glass,
water
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6. NECESSARY CONDITIONS FOR
COMBUSTION
• THERE ARE MAJORY 3 CONDITIONS FOR
COMBUSTION TO TAKE PLACE-
1. A COMBUSTIBLE SUBSTANCE ( A SUBSTANCE
WHICH UNDERGOES COMBUSTION)
2. OXYGEN i.e. A SUPPORTER OF COMBUSTION.
3. ATTAINMENT OF IGNITION TEMPERATURE.
Note- a fuel is a substance which undergoes
combustion i.e. It burns with air and releases a
lot of energy. PPT BY @RIDHIMAWAHI

7. WHAT IS IGNITION
TEMPERATURE?
• The ignition temperature is the minimum
temperature at which a substance starts to
burn. If the ignition temperature of the
substance is low, it means that it starts to burn
at a low temperature in less time. This is
because the minimum temperature for it to start
to burn is less. If the ignition temperature of the
substance is high, then it will start to burn on
heating it on a high temperature and will
relatively require more time.
• This is the reason why paper (and many other
substances) does not catch fire on room
temperature itself, because its ignition
temperature is much higher than room
temperature.
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8. APPLICATION- USE YOUR
MIND!
QUES- A PERSON WHOSE CLOTHES CATCH FIRE
IS COVERED WITH A BLANKET. WHAT DO YOU
THINK COULD BE THE POSSIBLE REASON?
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9. SOLUTION
• Well, we know that for fire to continue and
combustion to take place, oxygen is definitely
required. In fact, it is the supporter of
combustion. On spreading the blanket, the
supply of oxygen will be cut. And as a result,
the fire would extinguish.
QUES- WHY DOSEN’T A MATCHSTICK BURN AT
ROOM TEMPERATURE EVEN IN THE PRESENCE
OF OXYGEN?
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10. SOLUTION
• Every combustible substance has an ignition
temperature. The ignition temperature is the
lowest temperature at which a substance starts
to burn, and attainment of the ignition
temperature is must before combustion/ catching
fire. The ignition temperature of the matchstick is
much higher than room temperature, and this is
the reason why it catches fire on rubbing it
against the surface of the matchbox because the
heat produced by friction makes it attain its
ignition temperature.
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11. KEROSENE OIL IS USED TO
BURN WOOD AND COAL. WHY?
• For a substance to catch fire/ stat to burn, it
has to attain its ignition temperature. The
substances whose ignition temperature is very
high have to be heated up to a high
temperature in order to undergo combustion.
The substances such as wood and coal have
such a high ignition temperature, that a
matchstick can not provide enough heat (
make them attain the ignition temperature)
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12. Continuation...
• Now, the ignition temperature of the
kerosene is low. So, if it is sprinkled over the
wood and burnt by a lighted matchstick, it is
going to catch fire easily in very less time due
to its low ignition temperature. The heat
produced by kerosene makes the wood to
burn, and the heat produced by wood is
enough for the coal to start burning as it is
sufficient to make it attain its ignition
temperature.
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13. FLAMMABLE AND NON-FLAMMABLE
SUBSTANCES
FLAMMABLE SUBSTANCES
• These are the substances
whose ignition temperature
is very low and can catch
fire easily with a flame.
• Example- petrol, alcohol,
LPG
-----------------------------------------
NON- FLAMMABLE SUBSTANCES
• These are the substances
whose ignition temperature
is usually high and do not
catch fire or burn with a
flame.
• Example- coal, charcoal
-----------------------------------------
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14. HOW CAN FIRE BE
CONTROLLED?
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BY
@RIDHIMAWAHI

15. • The 3 very essential requirements for fire to
continue are-
1. Fuel, the substance that burns and
undergoes combustion
2. Presence of oxygen
3. Heat
If any of these components is removed, then
fire can be controlled. PPT BY @RIDHIMAWAHI

16. WE CONCLUDE THAT...
FIRE CAN BE CONTROLLED/ EXTINGUISHED BY
ANY OF THE FOLLOWING METHODS-
1. BY REMOVING THE FUEL i.e. THE
SUBSTANCE WHICH IS BURNING.
2. BY CUTTING OFF THE AIR SUPPLY, THIS
COULD BE DONE USING FIRE EXTINGUISHERS.
3. BY REMOVING THE HEAT.
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17. FIRE EXTINGUISHERS
Fire extinguishers are the
Substances that are used to
Stop/extinguish fire.
Water is one the most
common
Fire extinguishers, but
That is only for substances like
Wood and paper.
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18. • Water acts a fire extinguisher only for wood and
paper because it is able to extinguish fire by
cooling the substances. However, if any electric
equipment is on fire, then water may conduct
electricity and it may cause electric shocks.
• Also, if the fire involves petrol or oil, water is not
suitable for extinguishing the fire and this is
because water is heavier than oil and petrol, and
as a result the oil would start to float on the
surface of the water.
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19. TYPES OF COMBUSTION
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20. RAPID COMBUSTION
• It is the type of combustion which occurs in a
very short time, the substance burns rapidly
and a lot of heat and light is produced.
However, for this to happen the substance
needs to be heated first.
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21. SPONTANEOUS
COMBUSTION
• It is the type of combustion in which the
substance starts to burn on its own without
the involvement of any external heat.
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22. EXPLOSIONS
• This sudden type of combustion in which a lot
of sound, light and heat is produced. A lot of
gases are also produced.
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23. FLAME
• It is a hot glowing body of ignited gas which is
generated by something on fire.
• Whenever we burn something, vapours may be
released which are in gaseous state. The substances
which release the vapours on burning give flames.
THESE VAPOURS START TO BURN DUE TO WHICH
FLAME IS GIVEN OUT.
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24. STRUCTURE OF THE FLAME
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25. DETAIL-
• The innermost zone or the black zone is dark in
colour. This zone consists of the unburnt vapours
of the combustible substance and is the least hot
part of the flame.
• The middle zone is yellow in colour. It is the
luminous zone which has moderate temperature.
( partial combustion of the fuel)
• Outermost zone- blue in colour which is the
hottest part of the flame and hear complete
combustion takes place.
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26. Application-
Goldsmiths blow the outermost zone of a
flame with a metallic blow pipe for
melting gold and silver. ... The melting
point of gold and silver is very high.
therefore, goldsmiths need maximum
temperature. Hence goldsmith use
outermost part of the flame because it is
the hottest part of flame.
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27. FUELS AND
CALORIFIC VALUE
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