Here are some examples for those type of reactions. <span> Combustion reaction: CH4(g) + 2 O2(g) --> CO2(g) + 2 H2O(l) </span><span> Decomposition reaction: CaCO3(s) ---> CaO(s) + CO2(g)
It comes from the chemical reaction of The wax and the gas because the wax is made up of carbon-based chemicals so the gas and carbon make the candle light =)