Are all combustible substances fuels ? Justify your answer .

No, all combustible materials can't be considered as fuel. 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 arecombustible but not all combustible substances are fuels.

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.