Question

Which of the following is not a combustible substance?
A. Camphor
B. Glass
C. Straw
D. Alcohol

Answer 1

Combustible substances are such substances which readily react with oxygen. They burn in air to produce light and heat energy. They possess high enthalpy of combustion and have low ignition temperature.

Complete step by step answer:
In other words, we can say that the substances that can catch fire in presence of oxygen and release heat and light energy are referred as combustible substances. Examples of combustible substances are; alcohol, petrol, camphor, straw, diesel, etc. There are two types of combustion one is complete and other one is incomplete combustion. Complete combustion takes place when there is a sufficient supply of oxygen while incomplete combustion takes place due to the control supply of oxygen.
So, a substance will not be a combustible substance if it will not readily react with oxygen in the air. Also, a substance that is not combustible will not burn easily to produce heat or light energy. Examples of substances that are not combustible are; glass, stones, etc.
In glass the elements are in their higher oxidation states. As a result, they do not react with oxygen and thus glass does not catch fire. So, it is not combustible.

Hence, the correct option is (B).

Note:
Thus, glass does not readily react with the oxygen in the air and therefore it does not burn in air to produce heat and light energy. So, glass is a substance that is not combustible.. Straw, camphor, alcohol, petrol, diesel etc. catch fire easily to release heat energy and light energy. So, these are examples of combustible substances.