Question

Why some fuel burns with a flame and
some burns without a flame ?
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Answer 1

Answer:

The substances which vaporize during burning give flames and which don't vaporise does not produce flame

Explanation:

For example combustion of kerosene oil produces flame. On the other hand certain substances like coal do not vaporize and hence doesn't produce a flame.

Answer 2

✦✧ANSWER✦✧

burn without a flame. When fuel burns, some particle of the fuel vaporise and oxidised with oxygen, which is exothermic region. If the amount of energy coming out is in the visible region then flame have some colour. But if the energy coming out is outside the visible region then flame is not visible.

hope this will help you ♥