Question

Rapid combustion is:
A. When gas burns, it produces heat and light.
B. When material suddenly burns into flames
C. When there is evolution of heat
D. None of these

Answer 1

We need to know what is combustion and what are the different types of combustion. Combustion is a process by which a substance burns rapidly as a result of the reaction between a fuel and oxygen. The oxygen is often atmospheric oxygen since the atmospheric air has about 21% oxygen, and the requirement of oxygen for combustion is only about 16%. The reactants of combustion are fuel, oxygen and heat, and the end products are light, heat and smoke.

Complete step by step answer:
The technical term for burning is known as combustion. Combustion can be divided into several types depending on the reactants and the products.
Complete Combustion: A combination of fuel and oxygen where the reactants are completely burnt and utilized and leave a very limited amount of products is called complete combustion. For example, the combustion of carbon to give carbon dioxide.
Incomplete combustion: This combustion occurs when there is not enough oxygen to cause the complete combustion and thus produces less heat, light, and smoke.
Rapid combustion: This combustion requires external heat for the combustion to take place and continues until the fuel is completely burned. This produces an efficient amount of light and heat. One example is the burning of a candle where an external flame is required to light the candle and constant light and heat are produced till the wax of the candle has been exhausted.
Spontaneous combustion: This combustion does not require external heat energy for the reaction to take place. One example is the self-ignition of phosphorus if exposed to atmospheric air.
Explosive combustion: This type of combustion occurs at a very rapid pace producing sound energy in addition to heat and light. Burning of fireworks is an example of explosive combustion.
As per the question, the burning of gas to produce heat and light can be categorized under rapid combustion as the combustion will take place unless the gas available is fully exhausted.

So, the correct answer is Option A.

Note: It must be noted, that substances that undergo rapid combustion have a low ignition temperature. Hence, it is very important to supply adequate amounts of external energy to produce rapid combustion. For example, the burning of LPG gas in households for cooking is an example of rapid combustion and must be handled with care or else it can turn into explosive combustion.