Name some of the commonly used fuels,

:- Cow dung, wood, coal, charcoal, petrol, diesel, CNG

What is the difference between the burning of a candle and burning of a fuel like coal?
:- Candle burns with a flame, whereas coal does not
What does magnesium produce while burning?
:- Magnesium burns to form magnesium oxide and produces heat and light
Define combustion.
:- a chemical process in which a substance reacts with oxygen to give of heat is called combustion
What does charcoal produce after burning?
:- It produces carbon dioxide, heat, and light
What do you understand by fuel?
:- The substance that undergoes combustion is said to be combustible, it is also called a fuel
Explain why food is called as fuel for a body?
:- Food acts as fuel for body because in our body, food is broken down by reaction with oxygen heat is produced and
energy is released that helps in carrying out various life processes
Which type of energy does a body produce?
:- Adenosine triphosphate (ATP)
In which form does ATP is converted?
:- Adenosine Diphosphate (ADP)
What is necessary for combustion? :- Air.
This produces its own heat and light. Is it also some kind of combustion?
:-In the sun, heat light are produced by nuclear reaction. So this cannot be said as combustion.
How does during extreme heat of summer, whole forest catches fire easily?
:- during extreme heat of summer, at some places, dry grass catches fire. From the grass, it’s spreads to trees, and very
soon the whole forest is on fire. It is very difficult to control such fires.
If someone’s clothes catches fire, the person is covered with a blanket to extinguish fire. Can you guess why?
:-When someone’s clothes, catch fire, they are covered with blanket, extinguish the flames by cutting of the oxygen
supply that is required for combustion.
Why cannot a matchstick burn by itself?
:- This is because the ignition temperature of the matchsticks head is much higher than room temperature. It requires
additional heat, generated by friction when the Matchstick is rubbed against a rough surface.
Why do you have to use paper or kerosene oil to start fire in wood or coal?
:- paper or kerosene, oil are used to start fires in wood or coal because they have lower ignition temperatures than wood
or coal. This means they ignite more easily and produce enough heat to raise the temperature of wood or coal to at
ignition point, causing it to catch fire.
What do you understand by ignition temperature?
:- The lowest temperature at which a substance catches fire is called ignition temperature
What is the history of match stick?
:- History of match stick is very old. More than 5000 years ago, small pieces of pinewood dipped in sulphur were used as
matches in ancient Egypt. The modern safety match was developed only about 200 years ago.
By what does the head of match is made?
:- A mixture of antimony trisulphide, potassium chlorate, and white phosphorus with glue and starch was applied on head
of a match made of suitable wood
How does a matchstick work?
:- When a matchstick struck against a rough surface, white phosphorus present on its head got ignited due to the heat of
friction. They started the combustion of match.
Instead of white phosphorus, what is there on the head and rubbing surface of safety match these days?
:- These days, the head of safety match contains only antimony trisulphite and potassium chlorate. The rubbing surface
has powdered glass and a little red phosphorus (which is much less dangerous).
What happens when we struck the safety match against rubbing surface containing red phosphorus?
:- When the match is struck against the rubbing surface, some red phosphorus gets converted into white phosphorus. This
immediately reacts with potassium chlorate in Matchstick head to produce enough heat to ignite antimony trisulphite and
start the combustion.
Why do cooking oil catches fire when frying pan is kept for a long on a burning stove?
:- Cooking oil catches fire if a frying pan is kept on the burning stove for a long time because the cooking oil gets heated
to its ignition temperature, cause it to combust when kept over a burning stove for a long time.
Kerosene, oil and wood do not get fire on their own at room temperature. But if kerosene is heated a little, it will catch
fire. But if wood is heated a little, it would still not catch Fire. Give reason.
:- Kerosene and wood don't spontaneously combust at room temperature because they each have a specific Ignition
temperature. Kerosene has a lower ignition temperature than wood. When heated a little, kerosene reaches its ignition
temperature more readily, causing it to ignite. Wood, with its higher ignition temperature, requires more heat to reach the
point of ignition.
Why we should take special care in storing kerosene oil?
:- kerosene oil has lower ignition temperature, therefore it catches fire more easily. So, it is very crucial to store
kerosene oil with special care due to its inflammable nature.
Why does a paper cup containing water does not get burned but after sometime, water gets boiled, while paper
cup without water, get burned? Can you think of an explanation for this phenomenon?
:- That’s because the heat applied to the 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.Instead, the water heats up, and
eventually boils, transferring heat away from the paper. In contrast, an empty paper cup, without the water to
absorb heat, can quickly reach its ignition temperature and catch fire.
What do you understand by inflammable substances?
:- The substances, which have very low ignition temperature and can easily catch fire with a flame are called
inflammable substances
Tell some examples of inflammable substances.
:- Examples of inflammable substances are petrol, alcohol, LPG, etc.
Tell the full form of following:
1. CNG - compressed natural gas.
2. LPG - liquified petroleum gas
3. ATP - Adenosine triphosphate
4. ADP - Adenosine diphosphate
5. kJ - kilojoule
6. LNG - Liquified natural gas
How does a fire brigade extinguish the fire?
:- when a fire brigade arrives, it pour water on the fire. 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 of the supply of air. So, the fire is extinguished.
List the three essential requirements for producing Fire and also explain them.
:- 1) Fuel (source of heat energy, necessary for combustion or for ignition)
2) Air (to supply oxygen)
3) Heat (to raise the temperature of the fuel beyond the ignition temperature)
When the common fire extinguisher is can be used?
:- The most common fire extinguisher is water. But water works only when things like wood and paper are on fire.
Why common fire extinguisher cannot be used for electrical equipment?
:- If electrical equipment is on fire, water may conduct electricity and harm those trying to douse the fire
For what water fire extinguisher is not suitable?
:- Water is not suitable for fires involving oil, petrol, or electrical equipments
Why water fire extinguisher is not suitable for fires involving oil?
:- Water is not suitable for fires involving oil because water is heavier than oil. So, it sinks below the oil, and oil
keeps burning on the top.
Which extinguisher is used for fires involving electrical equipments and inflammable material materials?
:- carbon dioxide is the best extinguisher
Why carbon dioxide is the best extinguisher for fires involving electrical equipments and inflammable material
materials?
:- That’s because CO being heavier than oxygen, covers the fire like a blanket. Since the contact between the fuel
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and oxygen is cut off, the fire is controlled. The added advantage of CO is that in most cases, it does not harm the
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electrical appliances.
How do we get the supply of carbon dioxide?
:- It can be stored at height pressure as a liquid in cylinder.
Why it is cold, the best fire extinguisher?
:- When carbon dioxide released from cylinder, CO expands, enormously in volume and cools down. So, it not only
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forms a blanket around the fire, it also brings down the temperature of the fuel. That is why it is an excellent fire
extinguisher.
What is the another way to get carbon dioxide if we do not have the fire extinguisher?
:- Another way to get carbon dioxide is to release a lot of dry powder of chemicals like sodium bicarbonate (baking
soda) or potassium bicarbonate. Near the fire, these chemicals give off carbon dioxide.
Name one substance that burn at room temperature. :- phosphorus
Explain what do you mean by spontaneous combustion?
:- The type of combustion in which a material suddenly bursts into flames, without the application of any apparent
cause is called spontaneous combustion
Name three types of combustion.
:- 1) Rapid combustion
2) Spontaneous combustion
3) Explosion
Spontaneous combustion of which substance has resulted in many disastrous fires?
:- spontaneous combustion of cold dust has resulted in many disastrous fires in coal mines.
What is the reason behind spontaneous forest fires?
:- Spontaneous forest fires are sometimes due to the heat of the sun or due to lightning strike. However, most
forest fires are due to the carelessness of human beings.
What happens when you lit a firecracker?
:- When a cracker is ignited, a certain reaction takes place with the evolution of heat, light, and sound. A large
amount of gas formed in the reaction is liberated. Such a reaction is called explosion.
Under which circumstance can explosion can also take place?
:- Explosion can also take place of pressure is applied on the cracker
What is the colour of LPG flame?
:- Generally, blue in colour
What does blue flame of LPG indicate?
:- It indicates that combustion is taking place efficiently and in presence of sufficient oxygen
Which substance give flame?
:- The substances which vapour during burning, give flames
Why do charcoal do not produce any flame?
:- That’s because charcoal does not vaporise and so does not produce a flame during burning
Can you explain why a flame is observed at the end of a glass tube when one end is exposed to a candle flame and
a lit matchstick is brought near the other end?
:- When the glass tube is placed in the dark zone of the candle flame, the heat causes the wax to vaporise. These
wax vapours travel through the tube and, upon encountering the matchstick's flame, ignite, producing a visible
flame at the other end of the tube
Why does a circular blackish ring is formed on a glass plate placed into the luminous zone of the flame of Candle?
:- When a clean glass plate is introduced into the luminous zone of flame of candle, a circular blackish ring is
formed on the glass plate. It indicates the deposition of unburnt carbon particles present in the luminous zone of
the flame.
When a thin long copper wire is placed just inside the non-luminous zone of flame for about 30 seconds. The
portion of copper wire just outside the flame gets red hot. Give reason.
:- It indicates that the luminous zone of flame has high temperature. In fact, this part of the flame is the hottest
part.
Goldsmith blow the outer move zone of a flame with a metallic blowpipe for melting Gold and Silver. Why do they
use the outer zone of the flame?
:- That’s because it is the hottest part of the flame. This zone is where complete combustion occurs, resulting in
the highest temperature necessary to melt these high melting point metals like gold or silver
What qualities do a good fuel have?
:- A good fuel has following qualities-
1. It is cheap
2. It is readily available in the market
3. It burns easily in air at a moderate rate.
4. It produces large amount of heat.
5. It does not leave behind any undesirable substances
6. It must have high calorific value
7. It should have proper ignition temperature
8. It should be easy to transport
Suppose you were asked to boil a given quantity of water using cow dung, coal, and LPG as fuel. Which fuel would
you prefer?
:- When compared to cow dung and coal, LPG has all the qualities of a good fuel
It has more calorific value than cow dung which means it produces more heat. It can burn easily leaving behind no
harmful gas
What do you understand by calorific value?
:- The amount of heat energy produced on complete combustion of 1 KG of a fuel is called its calorific value.
In which unit the calorific value of a fuel is expressed? :- kilojoule per kg (kJ / kg)
Mention the calorific value of following fuels:-
1. Cow dung cake :- 6000-8000
2. Wood :- 17,000-22,000
3. Coal :- 25,000-33,000
4. Biogas :- 35,000-40,000
5. Petrol :- 45,000
6. Kerosene :- 45,000.
7. Diesel :- 45,000
8. Methane :- 50,000
9. CNG :- 50,000
10. LPG :- 55,000
11. Hydrogen :- 1,50,000
Wood is used as which type of fuel?
:- Wood is used as domestic and industrial fuel
Why people of rural areas are still using wood?
:- Due to its easy availability and low cost
What are the effects of burning wood?
:- 1. Burning of wood gives a lot of smoke, which is very harmful for human beings.
2. Smoke of wood causes many respiratory problems.
3. Also, trees provide us with useful substances which are lost when wood is used as fuel
4. Moreover, cutting of trees leads to deforestation, which is quite harmful to the environment.
What are the harmful products of burning of fuel?
:- The increasing fuel consumption has harmful effects on environment:-
1. Carbon fuels like wood, coal, petroleum, release unburnt carbon particles, which are very dangerous
pollutants
2. Incomplete combustion of these fuels gives carbon monoxide gas, it is a very poisonous gas
3. It leads to increased concentration of carbon dioxide in the air that is believed to cause global warming
4. Burning of coal/ diesel and petrol releases, sulphur dioxide or nitrogen dioxide, respectively. These oxides
when dissolved in rainwater forming acid, resulting in acid rain
What does unburnt carbon particles cause?
:- these fine particles are dangerous pollutants, causing respiratory diseases, such as asthma
Why it is advised, never to sleep in a room with burning or smouldering coal fire in it?
:- That’s because incomplete combustion of some fuels give carbon monoxide gas, it is a very poisonous gas. It is
dangerous to burn cool in a closed room. Carbon monoxide gas produced can kill person sleeping in that room.
What do you understand by global warming?
:- Global warming is the rise in the overall temperature of the atmosphere of the Earth. It leads to increased
concentration of carbon dioxide in the air.
What are the results of global warming?
:-This results in the melting of polar glaciers.
What does melting of polar glaciers cause?
:- Melting of glaciers leads to a rise in the sea level, causing floods in the coastal areas. Low lying coastal areas
may even be permanently submerged under water.
How does an acid rain happens?
:- Burning of coal and diesel releases, sulphur dioxide gas. It is an extremely suffocating and corrosive gas.
Moreover, petrol engines give of gas is oxides of nitrogen. Oxides of sulphur and nitrogen dissolve in rainwater and
acids. Such rain is called acid rain.
Write any three harmful effects of acid rain
:- 1) It causes damage to forest and crop production
2) It destroy the beauty of historical monuments
3) Acid rain effect the fertility and nature of soil, making it unsuitable for growth of plants
Mention the following information about the flame:-
1. Hottest part : outer zone.
2. Moderately hot part : middle zone
3. Least hot part : innermost zone
4. Part of complete combustion : outer zone
5. Part of partial combustion : middle zone
6. Zone of unburnt wax vapours : inner most zone
7. Colour of outer zone : blue
8. Colour of middle zone : yellow
9. Colour of innermost zone : black
10. Another name of inner most zone : Wick
11. Non-luminous zone : outermost zone
12. Luminous zone : middle zone
What is an ideal fuel?
:- An ideal fuel is defined by its efficiency, availability, and minimal environmental impact
Why hydrogen cannot be used as a domestic fuel for cooking instead of LPG?
:- Hydrogen is highly inflammable and explosive. Using it as domestic fuel is very dangerous, because even a small
spark can cause uncontrolled combustion leading to huge fires or explosions, posing serious risk to life and
property
Why it is preferred to not handle the gas of ourselves, but to ask our parents for help?
:- It is preferred that we should not handle the gas stove ourselves because using a gas stove involves risks like
gas leakage, fire, or burns, which require proper knowledge and safety precautions. Children may not be fully
aware of how to operate it safely, so it’s better to ask parents or responsible adults for help to prevent accidents.
What fuels are used for running automobiles?
:- Petrol, diesel, electricity, and CNG
Name a few fuels used in our homes
:- LPG, kerosene, wood, charcoal, and electricity
Define combustible and non-combustible substances
:- Combustible substances are materials that can catch fire and burn in the presence of air (oxygen) when heated.
Examples include wood, paper, kerosene, petrol, and LPG.
Non-combustible substances are materials that do not catch fire or burn easily, even when heated. Examples
include water, sand, glass, and metals like iron.

Tell the states of fuel. :- Solid, Liquid or Gas