Question

'' All combustible substances are not fuels'' give reason for your answer

Answer 1

Hi,

A combustible substance is the one which can burn. It does not necessarily mean that it would produce large amount of heat without leaving any residue. Thus all fuels are combustible but not all combustible substances are fuels.

A good fuel produces large amounts of energy and does not leave behind any undesirable substances. Also, it is cheap and is readily available.