Question

Which of the following example(s) represents spontaneous combustion?
(A) Burning of matchstick
(B) Burning of cooking gas.
(C) Ignition of a cracker
(D) Phosphorus burns in air at room temperature

Answer 1

Hint: Spontaneous combustion is the type of combustion that does not have any underlying cause and occurs due to the heat generated inside the system, for example, the dry hay catching fire in the scorching heat of summers.

Complete step by step solution:
We have studied that burning of a substance in presence of air is called combustion. Combustion cannot occur in the absence of oxygen.
If we light a candle in air and then cover it by a jar creating a vacuum, we will notice that the candle goes off and leaves a black mark on the jar. This black mark is due to the unburnt carbon particles. The reason behind this is, due to the absence of oxygen the combustion is not possible.
The combustion is of three types:
1. Rapid combustion
2. Spontaneous combustion and
3. Explosive combustion
-Rapid combustion is the type of combustion where heat is created in large amounts in a short duration of time. Example, the lighting of a gas stove.
-Spontaneous combustion is the type of combustion that occurs without any underlying cause. It occurs due to reactions happening within the system, at room temperature. Example, burning of sodium metal by coming in contact with moisture.
-Explosive combustion is the type of combustion where a large amount of heat is produced along with the light and sound. Example, nuclear weapon explosion.
Burning of matchstick causes heat in a short duration of time. Thus, it is rapid combustion.
Burning of cooking gas is an example of rapid combustion.
Ignition of crackers occurs with the production of huge amounts of heat, light and sound. Thus, it is an example of explosive combustion.
Burning of phosphorus at room temperature has no underlying cause and occurs as a result of chemical reactions occurring within the system.

Hence, option (D) is correct.

Note: Please note that combustion is a chemical reaction and not a physical reaction. When combustion occurs, it generates energy in the form of heat and light. The main point of difference between rapid combustion and spontaneous combustion is the involvement of external media to generate energy.