Question

why some substance burn with a flame while some burn without a flame

Answer 1

those substance burn with flame which has some volatile material in them as coal in starting burns with fire but as soon as volatile material goes out it do not give flame

Answer 2

Substances like camphor, candles, etc., burn with flame while substances like coal do not produce flame on burning. Substances when burn produce heat and light. Some of them also produce flame with light. The substances which vaporize during burning produces flame. As these substances heat up, like candles, the rising C-atoms produce light.Heat produces light, which is known as incandescence. This causes formation of visible flame. Flame color depends upon what is burning and how hot the object is.

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