A flame (from Latin flamma) is the visible, gaseous part of a fire. It is caused by a highly exothermic chemical reaction made in a thin zone. When flames are hot enough to have ionized gaseous components of sufficient density, they are then considered plasma. Mechanism. Color and temperature of a flame are dependent on the type of fuel involved in the combustion. For example, when a lighter is held to a candle, the applied heat causes the fuel molecules in the candle wax to vaporize.
https://en.wikipedia.org/wiki/Flame