Question

Water cannot be used as fire extinguisher to put out
A.Burning wood
B.Burning oil
C.Burning cloth
D.Burning charcoal

Answer 1

Hint:A fire needs three things to come into existence, namely a source of energy (like a spark or heat), a fuel (thing that will burn) and a source of oxygen. To put out a fire we simply need to remove one of the three necessary requirements.

Complete step by step answer:
Fire can be said to be the rapid and energetic oxidation of a fuel. In a typical fire, the source of oxygen is generally the air in the atmosphere. The more easily a fuel can accept oxygen, the more flammable it is. Water is a completely oxidized material. It cannot be oxidized further and thus will not burn. Water smothers the fire as it creates a barrier between the oxygen source and the fuel source. It also imparts a cooling effect as some energy is used up to convert the liquid water into water vapours.
But in case of oils or grease water is not able to put out the fire. We know that oils are much lighter than water and thus float on the surface of water. As a result, water cannot create a barrier between the fuel, in this case oil, and air. Furthermore, water vaporizes into the stream of oil, expanding it and causing it to spit out the oil. This makes the flame much bigger rather than putting it out.

Thus, the correct option is B.

Note:
In order to put out a fire we must use a substance that cannot be oxidized further or in other words, the substance should be completely oxidized, like carbon dioxide in which carbon cannot be further oxidized and can thus be used to put out the fire.