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Combustion and Flame

An example of explosion is

a) Burning of a gas stove.
b) Forest fires.
c) Burning of a cracker.
d) Burning of phosphorus in air at room temperature.

✔Answer

✔Solution

Correct Answer Is : Burning of a cracker.

Solution Is : In explosion, a sudden reaction takes place with the evolution of heat, light, sound and gas, e.g., ignition of a fire-cracker.

The colour of the flame in luminous zone is

a) Blue.
b) Red.
c) Yellow.
d) Black.

✔Answer

✔Solution

Correct Answer Is : Yellow.

Solution Is : In luminous zone, the flame is yellow. Yellow flame shows incomplete combustion due to insufficient supply of air.

Forest fire is a/an

a) Rapid combustion.
b) Spontaneous combustion.
c) Explosion.
d) Fast combustion.

✔Answer

✔Solution

Correct Answer Is : Spontaneous combustion.

Solution Is : In a spontaneous combustion, a material suddenly bursts into flames without any visible cause, e.g., Spontaneous fires in forests occur due to the heat of the sun.

An example of an inflammable substance is

a) Charcoal.
b) LPG.
c) Paper.
d) Wood.

✔Answer

✔Solution

Correct Answer Is : LPG.

Solution Is : An inflammable substance have a very low ignition temperature. Charcoal, paper and wood have high ignition temperatures, while LPG has a very low ignition temperature.

The head of a safety match contains

a) Antimony trisulphide and potassium chlorate.
b) Antimony chloride and potassium sulphide.
c) Antimony carbonate.
d) Potassium sulphide.

✔Answer

✔Solution

Correct Answer Is : Antimony trisulphide and potassium chlorate.

Solution Is : A mixture of antimony trisulphide, potassium chlorate and white phosphorus, with some glue and starch is applied on the head of a safety match, made of suitable wood.

When a frying pan containing cooking oil is kept for long on a burning stove then cooking oil catches fire because-

a) Its temperature is lower than its ignition temperature.
b) Its temperature is reached to its ignition temperature.
c) Its temperature is lower than critical temperature.
d) Its temperature is higher than critical temperature.

✔Answer

✔Solution

Correct Answer Is : Its temperature is reached to its ignition temperature.

Solution Is : A combustible substance cannot catch fire as long as its temperature is lower than its ignition temperature. Hence, when the temperature of cooking oil reaches to its ignition temperature (due to prolonged heating) then it catches fire.

The minimum temperature at which a substance catches fire is

a) Melting point.
b) Ignition temperature.
c) Boiling point.
d) Critical temperature.

✔Answer

✔Solution

Correct Answer Is : Ignition temperature.

Solution Is : Ignition temperature is the lowest temperature at which a substance catches fire.

The gas which supports combustion is-

a) CO₂come
b) He
c) O₂
d) Ne

✔Answer

✔Solution

Correct Answer Is : O₂

Solution Is : Oxygen is essential for burning. CO₂come extinguishes burning, He and Ne are unreactive gases.

The non-combustible substance among the following is

a) Coal.
b) Glass.
c) Wood.
d) Paper.

✔Answer

✔Solution

Correct Answer Is : Glass.

Solution Is : Glass is a non-combustible substance while coal,wood and paper are combustible substances. A chemical process in which a substance reacts with oxygen to give off heat is called combustion. substance that undergoes combustion is said to be combustible. It is also called a fuel.

Pollution can be reduced by using

a) Petrol.
b) Diesel.
c) Kerosene.
d) CNG.

✔Answer

✔Solution

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Class 8 Science Study Material

Combustion and Flame

An example of explosion is

Correct Answer Is : Burning of a cracker.

Solution Is : In explosion, a sudden reaction takes place with the evolution of heat, light, sound and gas, e.g., ignition of a fire-cracker.

The colour of the flame in luminous zone is

Correct Answer Is : Yellow.

Solution Is : In luminous zone, the flame is yellow. Yellow flame shows incomplete combustion due to insufficient supply of air.

Forest fire is a/an

Correct Answer Is : Spontaneous combustion.

Solution Is : In a spontaneous combustion, a material suddenly bursts into flames without any visible cause, e.g., Spontaneous fires in forests occur due to the heat of the sun.

An example of an inflammable substance is

Correct Answer Is : LPG.

Solution Is : An inflammable substance have a very low ignition temperature. Charcoal, paper and wood have high ignition temperatures, while LPG has a very low ignition temperature.

The head of a safety match contains

Correct Answer Is : Antimony trisulphide and potassium chlorate.

Solution Is : A mixture of antimony trisulphide, potassium chlorate and white phosphorus, with some glue and starch is applied on the head of a safety match, made of suitable wood.

When a frying pan containing cooking oil is kept for long on a burning stove then cooking oil catches fire because-

Correct Answer Is : Its temperature is reached to its ignition temperature.

Solution Is : A combustible substance cannot catch fire as long as its temperature is lower than its ignition temperature. Hence, when the temperature of cooking oil reaches to its ignition temperature (due to prolonged heating) then it catches fire.

The minimum temperature at which a substance catches fire is

Correct Answer Is : Ignition temperature.

Solution Is : Ignition temperature is the lowest temperature at which a substance catches fire.

The gas which supports combustion is-

Correct Answer Is : O2

Solution Is : Oxygen is essential for burning. CO2come extinguishes burning, He and Ne are unreactive gases.

The non-combustible substance among the following is

Correct Answer Is : Glass.

Solution Is : Glass is a non-combustible substance while coal,wood and paper are combustible substances. A chemical process in which a substance reacts with oxygen to give off heat is called combustion. substance that undergoes combustion is said to be combustible. It is also called a fuel.

Pollution can be reduced by using

Correct Answer Is : CNG.

Solution Is : CNG is Compressed Natural Gas. It produces comparatively less harmful products on burning than that produced by petrol, diesel etc.

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Correct Answer Is : O₂

Solution Is : Oxygen is essential for burning. CO₂come extinguishes burning, He and Ne are unreactive gases.