text: why is the centre of fire is blue?   a flame is the product of a highly exothermic reaction for example combustion, a self-sustaining oxidation reaction, or nuclear fusion in the sun. in layman's terms, a flame could be said to be, for example, the visible part of a fire.  the color and temperature of the flame are dependent on the type of fuel involved in the combustion. for example: when a lighter is held to a candle. this applied heat causes the fuel molecules to evaporate, in this state they can then react with oxygen, giving off enough heat in the exothermic reaction to sustain a consistent flame. the resulting increases in temperature tear apart some of the fuel molecules, forming various incomplete combustion products and free radicals. sufficient energy in the flame will excite the electrons in these products, which results in the emission of visible light. as the combustion temperature increases, so does the energy of the electromagnetic radiation given off by the flame. this is why the hottest visible flame is in the blue/violet region of the visible spectrum.