We have all experienced the transfer of heat from a flame to a pan of water and the first law of thermodynamics simply tells us that energy of the flame is used to heat the metal of the pan, heat the water, and even heat some of the surrounding air.
(We; have experienced; the transfer of heat from a flame to a pan of water and the first law of thermodynamics)
We
have experienced
the transfer of heat from a flame to a pan of water and the first law of thermodynamics