Question

When we burn a candle flame is produced, whereas when we burn a coal no flame can be seen. Why?

Answer 1

Only those substances, which vapourise during burning, produce flame (like kerosene, wax etc). Candle is made up of wax, which melts on heating. The molten wax rises through the wick and vapourises during burning resulting in the formation of flames. Coal, on the other hand does not vapourise on burning because of which no flame is observed.