NCERT Textbook: Combustion & Flame | Science & Technology for UPSC CSE PDF Download

 Page 1


COMBUSTION AND FLAME
COMBUSTION AND FLAME
W
e use different kinds of fuel for
various purposes at home, in
industry and for running
automobiles. Can you name a few fuels
used in our homes? Name a few fuels
used in trade and industry. What fuels
are used for running automobiles? Your
list will contain fuels like cowdung,
wood, coal, charcoal, petrol, diesel,
compressed natural gas (CNG), etc.
You are familiar with the burning of a
candle. What is the difference between the
burning of a candle and the burning of a
fuel like coal? May be you were able to
guess right: candle burns with a flame
whereas coal does not. Similarly, you will
find many other materials burning
without a flame. Let us study the chemical
process of burning and the types of flame
produced during this process.
4.1 What is Combustion?
Recall the activity of burning of
magnesium ribbon performed in
Class VII. We learnt that magnesium
burns to form magnesium oxide and
produces heat and light (Fig. 4.1).
We can perform a similar activity with
a piece of charcoal. Hold the piece with
a pair of tongs and bring it near the
flame of a candle or a  Bunsen burner.
What do you observe?
We find that charcoal burns in air.
We know that coal, too, burns  in air
producing carbon dioxide, heat and
light.
We were told that
food is a fuel for
our body.
Fig. 4.1 : Burning of magnesium
A chemical process in which a
substance reacts with oxygen to give
off heat is called combustion. The
substance that undergoes combustion
is said to be combustible. It is also called
a fuel. The fuel may be solid, liquid or
gas. Sometimes, light is also given off
during combustion, either as a flame or
as a glow.
In the reactions mentioned
above magnesium and charcoal are
combustible substances.
2024-25
Page 2


COMBUSTION AND FLAME
COMBUSTION AND FLAME
W
e use different kinds of fuel for
various purposes at home, in
industry and for running
automobiles. Can you name a few fuels
used in our homes? Name a few fuels
used in trade and industry. What fuels
are used for running automobiles? Your
list will contain fuels like cowdung,
wood, coal, charcoal, petrol, diesel,
compressed natural gas (CNG), etc.
You are familiar with the burning of a
candle. What is the difference between the
burning of a candle and the burning of a
fuel like coal? May be you were able to
guess right: candle burns with a flame
whereas coal does not. Similarly, you will
find many other materials burning
without a flame. Let us study the chemical
process of burning and the types of flame
produced during this process.
4.1 What is Combustion?
Recall the activity of burning of
magnesium ribbon performed in
Class VII. We learnt that magnesium
burns to form magnesium oxide and
produces heat and light (Fig. 4.1).
We can perform a similar activity with
a piece of charcoal. Hold the piece with
a pair of tongs and bring it near the
flame of a candle or a  Bunsen burner.
What do you observe?
We find that charcoal burns in air.
We know that coal, too, burns  in air
producing carbon dioxide, heat and
light.
We were told that
food is a fuel for
our body.
Fig. 4.1 : Burning of magnesium
A chemical process in which a
substance reacts with oxygen to give
off heat is called combustion. The
substance that undergoes combustion
is said to be combustible. It is also called
a fuel. The fuel may be solid, liquid or
gas. Sometimes, light is also given off
during combustion, either as a flame or
as a glow.
In the reactions mentioned
above magnesium and charcoal are
combustible substances.
2024-25
Activity 4.2
(Caution : Be careful while handling
burning candle).
Fix a lighted candle on a table. Put
a glass chimney over the candle and
rest it on a few wooden blocks in
such a way that air can enter the
Table 4.1 : Combustible and Non-
combustible Substances
Material Combustible Non-
combustible
Wood
Paper
Iron nails
Kerosene oil
Stone piece
Straw
Charcoal
Matchsticks
Glass
Activity 4.1
Collect some materials like straw,
matchsticks, kerosene oil, paper,
iron nails, stone pieces, glass etc.
Under the supervision of your
teacher try to burn each of these
materials one by one. If combustion
takes place mark the material
combustible, otherwise mark it
non-combustible (Table 4.1).
(a) (b)   (c)
Fig. 4.2: Experiment to show that air is
essential for burning
Rightly so. In our body
food is broken down by
reaction with oxygen and
heat is produced. We
learnt that in Class VII.
Can you name some more
substances which are combustible? You
can add  those to Table 4.1.
Let us investigate conditions under
which combustion takes place.
COMBUSTION AND FLAME 41
chimney [Fig. 4.2(a)]. Observe what
happens to the flame. Now remove
the blocks and let the chimney rest
on the table [Fig. 4.2(b)]. Again
observe the flame. Finally, put a
glass plate over the chimney [Fig.
4.2(c)]. Watch the flame again. What
happens in the three cases? Does
the flame flicker off? Does it flicker
and give  smoke? Does it burn
unaffected? Can you infer anything
at all about the role played by air in
the process of burning?
We find that for combustion, air is
necessary. The candle burns freely in
case (a) when air can enter the
chimney from below. In case (b), when
air does not enter the chimney from
below, the flame flickers and produces
smoke. In case (c), the flame finally
goes off because the air is not
available.
2024-25
Page 3


COMBUSTION AND FLAME
COMBUSTION AND FLAME
W
e use different kinds of fuel for
various purposes at home, in
industry and for running
automobiles. Can you name a few fuels
used in our homes? Name a few fuels
used in trade and industry. What fuels
are used for running automobiles? Your
list will contain fuels like cowdung,
wood, coal, charcoal, petrol, diesel,
compressed natural gas (CNG), etc.
You are familiar with the burning of a
candle. What is the difference between the
burning of a candle and the burning of a
fuel like coal? May be you were able to
guess right: candle burns with a flame
whereas coal does not. Similarly, you will
find many other materials burning
without a flame. Let us study the chemical
process of burning and the types of flame
produced during this process.
4.1 What is Combustion?
Recall the activity of burning of
magnesium ribbon performed in
Class VII. We learnt that magnesium
burns to form magnesium oxide and
produces heat and light (Fig. 4.1).
We can perform a similar activity with
a piece of charcoal. Hold the piece with
a pair of tongs and bring it near the
flame of a candle or a  Bunsen burner.
What do you observe?
We find that charcoal burns in air.
We know that coal, too, burns  in air
producing carbon dioxide, heat and
light.
We were told that
food is a fuel for
our body.
Fig. 4.1 : Burning of magnesium
A chemical process in which a
substance reacts with oxygen to give
off heat is called combustion. The
substance that undergoes combustion
is said to be combustible. It is also called
a fuel. The fuel may be solid, liquid or
gas. Sometimes, light is also given off
during combustion, either as a flame or
as a glow.
In the reactions mentioned
above magnesium and charcoal are
combustible substances.
2024-25
Activity 4.2
(Caution : Be careful while handling
burning candle).
Fix a lighted candle on a table. Put
a glass chimney over the candle and
rest it on a few wooden blocks in
such a way that air can enter the
Table 4.1 : Combustible and Non-
combustible Substances
Material Combustible Non-
combustible
Wood
Paper
Iron nails
Kerosene oil
Stone piece
Straw
Charcoal
Matchsticks
Glass
Activity 4.1
Collect some materials like straw,
matchsticks, kerosene oil, paper,
iron nails, stone pieces, glass etc.
Under the supervision of your
teacher try to burn each of these
materials one by one. If combustion
takes place mark the material
combustible, otherwise mark it
non-combustible (Table 4.1).
(a) (b)   (c)
Fig. 4.2: Experiment to show that air is
essential for burning
Rightly so. In our body
food is broken down by
reaction with oxygen and
heat is produced. We
learnt that in Class VII.
Can you name some more
substances which are combustible? You
can add  those to Table 4.1.
Let us investigate conditions under
which combustion takes place.
COMBUSTION AND FLAME 41
chimney [Fig. 4.2(a)]. Observe what
happens to the flame. Now remove
the blocks and let the chimney rest
on the table [Fig. 4.2(b)]. Again
observe the flame. Finally, put a
glass plate over the chimney [Fig.
4.2(c)]. Watch the flame again. What
happens in the three cases? Does
the flame flicker off? Does it flicker
and give  smoke? Does it burn
unaffected? Can you infer anything
at all about the role played by air in
the process of burning?
We find that for combustion, air is
necessary. The candle burns freely in
case (a) when air can enter the
chimney from below. In case (b), when
air does not enter the chimney from
below, the flame flickers and produces
smoke. In case (c), the flame finally
goes off because the air is not
available.
2024-25
SCIENCE 42
Activity 4.3
Place a piece of burning wood or
charcoal on an iron plate or Tawa.
Cover it with a glass jar or a
tumbler, or a transparent plastic jar.
Observe what happens. Does
charcoal stop burning after
sometime? Can you think of the
reason why it stops burning?
You might have heard that when the
clothes of a person catch fire, the person
We have read that the sun
produces its own heat and
light. Is it also some kind of
combustion?
In the sun, heat and light are
produced by nuclear reactions. You
will learn about this process in higher
classes.
During extreme heat
of summer, at some
places dry grass
catches fire. From
the grass, it spreads
to trees, and very
soon the whole forest
is on fire (Fig. 4.4). It
is very difficult to
control such fires.
Fig. 4.4 : Forest fire
Fig. 4.3 : Blanket wrapped around a person
whose clothes caught fire
Now recall some of your experiences.
Does a matchstick burn by itself?
How does it burn?
You must have had an experience of
burning a piece of paper. Does it burn
when a burning matchstick is brought
near it?
Can you burn a piece of wood by
bringing a lighted matchstick near it?
Why do you have to use paper or
kerosene oil to start fire in wood or coal?
Have you heard of forest fires?
is covered with a blanket to extinguish
fire (Fig. 4.3). Can you guess why?
2024-25
Page 4


COMBUSTION AND FLAME
COMBUSTION AND FLAME
W
e use different kinds of fuel for
various purposes at home, in
industry and for running
automobiles. Can you name a few fuels
used in our homes? Name a few fuels
used in trade and industry. What fuels
are used for running automobiles? Your
list will contain fuels like cowdung,
wood, coal, charcoal, petrol, diesel,
compressed natural gas (CNG), etc.
You are familiar with the burning of a
candle. What is the difference between the
burning of a candle and the burning of a
fuel like coal? May be you were able to
guess right: candle burns with a flame
whereas coal does not. Similarly, you will
find many other materials burning
without a flame. Let us study the chemical
process of burning and the types of flame
produced during this process.
4.1 What is Combustion?
Recall the activity of burning of
magnesium ribbon performed in
Class VII. We learnt that magnesium
burns to form magnesium oxide and
produces heat and light (Fig. 4.1).
We can perform a similar activity with
a piece of charcoal. Hold the piece with
a pair of tongs and bring it near the
flame of a candle or a  Bunsen burner.
What do you observe?
We find that charcoal burns in air.
We know that coal, too, burns  in air
producing carbon dioxide, heat and
light.
We were told that
food is a fuel for
our body.
Fig. 4.1 : Burning of magnesium
A chemical process in which a
substance reacts with oxygen to give
off heat is called combustion. The
substance that undergoes combustion
is said to be combustible. It is also called
a fuel. The fuel may be solid, liquid or
gas. Sometimes, light is also given off
during combustion, either as a flame or
as a glow.
In the reactions mentioned
above magnesium and charcoal are
combustible substances.
2024-25
Activity 4.2
(Caution : Be careful while handling
burning candle).
Fix a lighted candle on a table. Put
a glass chimney over the candle and
rest it on a few wooden blocks in
such a way that air can enter the
Table 4.1 : Combustible and Non-
combustible Substances
Material Combustible Non-
combustible
Wood
Paper
Iron nails
Kerosene oil
Stone piece
Straw
Charcoal
Matchsticks
Glass
Activity 4.1
Collect some materials like straw,
matchsticks, kerosene oil, paper,
iron nails, stone pieces, glass etc.
Under the supervision of your
teacher try to burn each of these
materials one by one. If combustion
takes place mark the material
combustible, otherwise mark it
non-combustible (Table 4.1).
(a) (b)   (c)
Fig. 4.2: Experiment to show that air is
essential for burning
Rightly so. In our body
food is broken down by
reaction with oxygen and
heat is produced. We
learnt that in Class VII.
Can you name some more
substances which are combustible? You
can add  those to Table 4.1.
Let us investigate conditions under
which combustion takes place.
COMBUSTION AND FLAME 41
chimney [Fig. 4.2(a)]. Observe what
happens to the flame. Now remove
the blocks and let the chimney rest
on the table [Fig. 4.2(b)]. Again
observe the flame. Finally, put a
glass plate over the chimney [Fig.
4.2(c)]. Watch the flame again. What
happens in the three cases? Does
the flame flicker off? Does it flicker
and give  smoke? Does it burn
unaffected? Can you infer anything
at all about the role played by air in
the process of burning?
We find that for combustion, air is
necessary. The candle burns freely in
case (a) when air can enter the
chimney from below. In case (b), when
air does not enter the chimney from
below, the flame flickers and produces
smoke. In case (c), the flame finally
goes off because the air is not
available.
2024-25
SCIENCE 42
Activity 4.3
Place a piece of burning wood or
charcoal on an iron plate or Tawa.
Cover it with a glass jar or a
tumbler, or a transparent plastic jar.
Observe what happens. Does
charcoal stop burning after
sometime? Can you think of the
reason why it stops burning?
You might have heard that when the
clothes of a person catch fire, the person
We have read that the sun
produces its own heat and
light. Is it also some kind of
combustion?
In the sun, heat and light are
produced by nuclear reactions. You
will learn about this process in higher
classes.
During extreme heat
of summer, at some
places dry grass
catches fire. From
the grass, it spreads
to trees, and very
soon the whole forest
is on fire (Fig. 4.4). It
is very difficult to
control such fires.
Fig. 4.4 : Forest fire
Fig. 4.3 : Blanket wrapped around a person
whose clothes caught fire
Now recall some of your experiences.
Does a matchstick burn by itself?
How does it burn?
You must have had an experience of
burning a piece of paper. Does it burn
when a burning matchstick is brought
near it?
Can you burn a piece of wood by
bringing a lighted matchstick near it?
Why do you have to use paper or
kerosene oil to start fire in wood or coal?
Have you heard of forest fires?
is covered with a blanket to extinguish
fire (Fig. 4.3). Can you guess why?
2024-25
COMBUSTION AND FLAME 43
We find that a combustible substance
cannot catch fire or burn as long as its
temperature is lower than its ignition
temperature. Have you ever seen
cooking oil catching fire when a frying
pan is kept for long on a burning stove?
Kerosene oil and wood do not catch fire
on their own at room temperature. But,
if kerosene oil is heated a little, it will
catch fire. But if wood is heated a little,
it would still not catch fire. Does it mean
that ignition temperature of kerosene oil
is lower than that of wood? Does it mean
that we need to take special care in
storing kerosene oil? The following
activity shows that it is essential for a
substance to reach ignition temperature
to burn.
Activity 4.4
(Caution : Be careful while handling
burning candle).
Make two paper cups by folding a
sheet of paper. Pour about 50 mL of
water in one of the cups. Heat both
the cups separately with a candle
(Fig. 4.5). What do you observe?
The history of the matchstick is very
old. More than five thousand years
ago small pieces of pinewood dipped
in sulphur were used as matches in
ancient Egypt. The modern safety
match was developed only about two
hundred years ago.
A mixture of antimony trisulphide,
potassium chlorate and white
phosphorus with some glue and
starch was applied on the head of a
match made of suitable wood. When
struck against a rough surface, white
phosphorus got ignited due to the heat
of friction. This started the
combustion of the match. However,
white phosphorus proved to be
dangerous both for the workers
involved in the manufacturing of
matches and for the users.
These days the head of the safety
match contains only antimony
trisulphide and potassium chlorate.
The rubbing surface has powdered
glass and a little red phosphorus
(which is much less dangerous).
When the match is struck against
the rubbing surface, some red
phosphorus gets converted into white
phosphorus. This immediately reacts
with potassium chlorate in the
matchstick head to produce enough
heat to ignite antimony trisulphide
and start the combustion.
Do these experiences tell you that
different substances catch fire at
different temperatures?
The lowest temperature at which a
substance catches fire is called its
ignition temperature.
Can you tell now why a matchstick
does not catch fire on its own at room
temperature? Why does the matchstick
start burning on rubbing it on the side
of the matchbox?
Fig. 4.5 : Heating water in a paper cup
water
paper
cups
What happens to the empty paper
cup? What happens to the paper cup
with water? Does water in this cup
become hot?
2024-25
Page 5


COMBUSTION AND FLAME
COMBUSTION AND FLAME
W
e use different kinds of fuel for
various purposes at home, in
industry and for running
automobiles. Can you name a few fuels
used in our homes? Name a few fuels
used in trade and industry. What fuels
are used for running automobiles? Your
list will contain fuels like cowdung,
wood, coal, charcoal, petrol, diesel,
compressed natural gas (CNG), etc.
You are familiar with the burning of a
candle. What is the difference between the
burning of a candle and the burning of a
fuel like coal? May be you were able to
guess right: candle burns with a flame
whereas coal does not. Similarly, you will
find many other materials burning
without a flame. Let us study the chemical
process of burning and the types of flame
produced during this process.
4.1 What is Combustion?
Recall the activity of burning of
magnesium ribbon performed in
Class VII. We learnt that magnesium
burns to form magnesium oxide and
produces heat and light (Fig. 4.1).
We can perform a similar activity with
a piece of charcoal. Hold the piece with
a pair of tongs and bring it near the
flame of a candle or a  Bunsen burner.
What do you observe?
We find that charcoal burns in air.
We know that coal, too, burns  in air
producing carbon dioxide, heat and
light.
We were told that
food is a fuel for
our body.
Fig. 4.1 : Burning of magnesium
A chemical process in which a
substance reacts with oxygen to give
off heat is called combustion. The
substance that undergoes combustion
is said to be combustible. It is also called
a fuel. The fuel may be solid, liquid or
gas. Sometimes, light is also given off
during combustion, either as a flame or
as a glow.
In the reactions mentioned
above magnesium and charcoal are
combustible substances.
2024-25
Activity 4.2
(Caution : Be careful while handling
burning candle).
Fix a lighted candle on a table. Put
a glass chimney over the candle and
rest it on a few wooden blocks in
such a way that air can enter the
Table 4.1 : Combustible and Non-
combustible Substances
Material Combustible Non-
combustible
Wood
Paper
Iron nails
Kerosene oil
Stone piece
Straw
Charcoal
Matchsticks
Glass
Activity 4.1
Collect some materials like straw,
matchsticks, kerosene oil, paper,
iron nails, stone pieces, glass etc.
Under the supervision of your
teacher try to burn each of these
materials one by one. If combustion
takes place mark the material
combustible, otherwise mark it
non-combustible (Table 4.1).
(a) (b)   (c)
Fig. 4.2: Experiment to show that air is
essential for burning
Rightly so. In our body
food is broken down by
reaction with oxygen and
heat is produced. We
learnt that in Class VII.
Can you name some more
substances which are combustible? You
can add  those to Table 4.1.
Let us investigate conditions under
which combustion takes place.
COMBUSTION AND FLAME 41
chimney [Fig. 4.2(a)]. Observe what
happens to the flame. Now remove
the blocks and let the chimney rest
on the table [Fig. 4.2(b)]. Again
observe the flame. Finally, put a
glass plate over the chimney [Fig.
4.2(c)]. Watch the flame again. What
happens in the three cases? Does
the flame flicker off? Does it flicker
and give  smoke? Does it burn
unaffected? Can you infer anything
at all about the role played by air in
the process of burning?
We find that for combustion, air is
necessary. The candle burns freely in
case (a) when air can enter the
chimney from below. In case (b), when
air does not enter the chimney from
below, the flame flickers and produces
smoke. In case (c), the flame finally
goes off because the air is not
available.
2024-25
SCIENCE 42
Activity 4.3
Place a piece of burning wood or
charcoal on an iron plate or Tawa.
Cover it with a glass jar or a
tumbler, or a transparent plastic jar.
Observe what happens. Does
charcoal stop burning after
sometime? Can you think of the
reason why it stops burning?
You might have heard that when the
clothes of a person catch fire, the person
We have read that the sun
produces its own heat and
light. Is it also some kind of
combustion?
In the sun, heat and light are
produced by nuclear reactions. You
will learn about this process in higher
classes.
During extreme heat
of summer, at some
places dry grass
catches fire. From
the grass, it spreads
to trees, and very
soon the whole forest
is on fire (Fig. 4.4). It
is very difficult to
control such fires.
Fig. 4.4 : Forest fire
Fig. 4.3 : Blanket wrapped around a person
whose clothes caught fire
Now recall some of your experiences.
Does a matchstick burn by itself?
How does it burn?
You must have had an experience of
burning a piece of paper. Does it burn
when a burning matchstick is brought
near it?
Can you burn a piece of wood by
bringing a lighted matchstick near it?
Why do you have to use paper or
kerosene oil to start fire in wood or coal?
Have you heard of forest fires?
is covered with a blanket to extinguish
fire (Fig. 4.3). Can you guess why?
2024-25
COMBUSTION AND FLAME 43
We find that a combustible substance
cannot catch fire or burn as long as its
temperature is lower than its ignition
temperature. Have you ever seen
cooking oil catching fire when a frying
pan is kept for long on a burning stove?
Kerosene oil and wood do not catch fire
on their own at room temperature. But,
if kerosene oil is heated a little, it will
catch fire. But if wood is heated a little,
it would still not catch fire. Does it mean
that ignition temperature of kerosene oil
is lower than that of wood? Does it mean
that we need to take special care in
storing kerosene oil? The following
activity shows that it is essential for a
substance to reach ignition temperature
to burn.
Activity 4.4
(Caution : Be careful while handling
burning candle).
Make two paper cups by folding a
sheet of paper. Pour about 50 mL of
water in one of the cups. Heat both
the cups separately with a candle
(Fig. 4.5). What do you observe?
The history of the matchstick is very
old. More than five thousand years
ago small pieces of pinewood dipped
in sulphur were used as matches in
ancient Egypt. The modern safety
match was developed only about two
hundred years ago.
A mixture of antimony trisulphide,
potassium chlorate and white
phosphorus with some glue and
starch was applied on the head of a
match made of suitable wood. When
struck against a rough surface, white
phosphorus got ignited due to the heat
of friction. This started the
combustion of the match. However,
white phosphorus proved to be
dangerous both for the workers
involved in the manufacturing of
matches and for the users.
These days the head of the safety
match contains only antimony
trisulphide and potassium chlorate.
The rubbing surface has powdered
glass and a little red phosphorus
(which is much less dangerous).
When the match is struck against
the rubbing surface, some red
phosphorus gets converted into white
phosphorus. This immediately reacts
with potassium chlorate in the
matchstick head to produce enough
heat to ignite antimony trisulphide
and start the combustion.
Do these experiences tell you that
different substances catch fire at
different temperatures?
The lowest temperature at which a
substance catches fire is called its
ignition temperature.
Can you tell now why a matchstick
does not catch fire on its own at room
temperature? Why does the matchstick
start burning on rubbing it on the side
of the matchbox?
Fig. 4.5 : Heating water in a paper cup
water
paper
cups
What happens to the empty paper
cup? What happens to the paper cup
with water? Does water in this cup
become hot?
2024-25
SCIENCE 44
If we continue heating
the cup, we can even boil
water in the paper cup.
Can you think of an
explanation for this
phenomenon?
The heat supplied to
the paper cup is
transferred to water by
conduction. So, in the
presence of water, the
ignition temperature of
paper is not reached.
Hence, it does not burn.
The substances which
have very low ignition
temperature and can
easily catch fire with
a flame are called
inflammable substances. Examples of
inflammable substances are petrol,
alcohol, Liquified Petroleum Gas (LPG)
etc. Can you list some more inflammable
substances?
4.2 How Do We Control Fire?
You must have seen or heard of fire
breaking out in homes, shops and
factories. If you have seen such an
accident, write a short description in
your note book. Also, share the
experience with your classmates.
It is important that all of us
know the telephone numbers
of the fire service.
Fig. 4.6: Firemen extinguish the fire by throwing water under pressure
Find out the telephone number of the
fire service in your area. If a fire
breaks out in your house or in your
neighbourhood, the first thing to do
is to call the fire service.
Does your city/town have a fire
brigade station?
When a fire brigade arrives, what
does it do? It pours water on the fire
(Fig. 4.6). Water cools the combustible
material so that its temperature is
brought below its ignition
temperature. This prevents the fire
from spreading. Water vapours also
surround the combustible material,
helping in cutting off the supply of air.
So, the fire is extinguished.
You have learnt that there are three
essential requirements for producing
fire. Can you list these requirements?
These are: fuel, air (to supply
oxygen) and heat (to raise the
temperature of the fuel beyond the
ignition temperature). Fire can be
controlled by removing one or more of
these requirements. The job of a fire
extinguisher is to cut off the supply of
air, or to bring down the temperature
of the fuel, or both. Notice that the fuel
2024-25