Question

Which of the following is non-combustible?
a.) Sand
b.) Iron
c.) Glass
d.) All of the above

Answer 1

Hint: So, here the combustible material is something that can combust (burn) in air. Flammable materials are combustible materials that ignite easily at ambient temperatures.
Step by step solution:
Substances which burn in air to produce heat and light are called combustible substances. A combustible material ignites with some effort and a flammable material catches fire immediately on exposure to flame. Example: wood, coal, charcoal, kerosene, petrol, diesel, liquefied petroleum gas (LPG), compressed natural gas (CNG) etc.
Non combustible substances are those which do not burn on being exposed to flame. For example: stone, glass, iron nails, etc.
Glass consists mostly of oxides such as silica. Because the elements are in their highest oxidation states, they will not react with oxygen. Thus, glass is not combustible. Normally sand is non-combustible.
Most combustion we see involves things reacting with the oxygen in air. Most combustion reactions are a self-sustaining exothermic reaction of some substance with oxygen gas. Many metals react to give metal oxides (example: magnesium, spectacularly when lit; iron, only when hot and finely divided).
So, from the above explanation we can say that option “D” is the correct option.

Note: Sometimes sand and iron can catch fire, in case of iron it depends on its exposure in the air or temperature. In case of sand it depends on the composition of sand and in pure chemical state it will not catch fire.