Question

1) How do we control fire ?
i) Explain each types

2) Explain types of combustion ?
i) Explain with types of combustion

3)Explain Flame ?
i) With flame diagram

4) Explain structure of flame ?
i) With different zone of a
candle flame

5) What is fuel ?
i) Explain with example and diagram of fuel ?

Class 8 .
Science .
Chapter 4 - Combustion and flame

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Answer 1

1) Methods for controlling fire are -:

• By Using Water → The most common extinguisher of fire is water, but we can only use it to extinguish materials like wood, paper, etc that are on fire. If we use water to extinguish an electrical appliance on fire it can be really harmful since water is a good conductor of electricity. Water can also not be used to extinguish oil or petrol fires since water will float over them and the fire can spread.

• By Using Carbon Dioxide → Carbon dioxide is known to be the best fire extinguisher in the cause where inflammable materials like oil are on fire. Electrical fires can also be extinguished using carbon dioxide. Since carbon dioxide is heavier than air it cuts off the oxygen supply and extinguishes the fire.

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2) There are three types of combustion. They are →

• Spontaneous Combustion ⇒ This type of combustion takes place on its own at room temperature. It occurs in the materials that have a lesser ignition temperature than the room temperature.

• Rapid Combustion ⇒ This type of combustion occurs rapidly producing a lot of heat and light within a short period of time.

• Explosive Combustion ⇒ This type of combustion occurs extremely fast and produces a lot of heat and light along with loud sound.

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3) Flame is the hot luminous gas which emerges from a substance that is burning. They are a result of the substances that vaporize when burned. The flame consist of three zones as mentioned in the diagram.

(Required diagram attached)

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4) The flame consists of three zones. They are →

• Dark Inner Zone ⇒ This is black in colour and it is the innermost close to the wick. Here no combustion takes place and it is the least hot part of the flame.

• Middle Zone ⇒ It is yellow and luminous. Here partial or incomplete combustion takes place and this part of the flame is somewhat hot.

• Outermost Zone ⇒ It is blue in colour and faintly visible. Here complete combustion takes place and it is the hottest part of the candle.

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5) The substance that undergoes combustion is known as fuel. For example-: Petrol, kerosene, coal, etc. We have three types of fuels. →

• Solid Fuel
• Liquid Fuel
• Gaseous Fuel

The characteristics of a good fuel are that it is easily available and cheap in price. It should be able to burn in air with a normal temperature and shall not leave out a large amount of heat. A good fuel doesn't leave out any unwanted substance.

There isn't any fuel that can be considered the best or an ideal fuel. A fuel that fulfils our requirements and follows the characteristics mentioned above is a good fuel.

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Answer 2

1) How do we control fire ?

Water - Water helps us to control fire

• Water cools the combustion material so that its temperature brought below
• Water vapours are also surrounded the combustible material helping in cutting off the supply of air so the fire is extinguished .

i) Explain each types

• There are fuel , air to supply Oxygen to heat to raise the temperature of the fuel beyond the ignition temperature .

• The job of fire extinguisher and is to cut off the supply of air or to bring down the temperature of the fuel or both notice that the fuel in most cases can't be eliminated

2) Explain types of combustion ?

Types of combustion -

Rapid combustion - We find that the gas burns rapidly and produces heat and light . Such combustion is known as rapid combustion .

Spontaneous combustion - The type of combustion in which material suddenly burst into flames without the application of apartment cause it is called spontaneous combustion

Explosive combustion - a large amount of gas formed in the reaction is liberated . Such a reaction is called explosion combustion .

3 ) Explain Flame ?

Flame is the region where confusion combustion of gaseous substances take place .

4 ) Structure of flame :

Refer to attachment . You can see the diagram of Structure of flame .

• The first zone is called the Outer zone.
• The second zone is called the Middle zone.
• The third zone is called as Inner zone.

5) What is fuel ?

The sources of heat energetic for domestic and industrial purposes are mainly wood , charcoal , petrol . Kerosene etc.... These substances are called fuels .