Combustion Reactions Element or compound reacts with oxygen, releasing energy (heat, light) O2 always a reactant Hydrocarbon often other reactant Products = CO2 and H2O (when reactant = hydrocarbon)

Hydrocarbons Alkanes (CnH2n + 2) Methane Hexane Ethane Heptane Propane Octane Butane Nonane Pentane Decane

COMPLETE combustion of a hydrocarbon…  CO2 + H2O + energy/heat What happens if O2 is limited?

Combustion of heptane Combustion of glucose C6H12O6 + O2  CO2 + H2O C7H16 + O2  CO2 + H2O Combustion of glucose C6H12O6 + O2  CO2 + H2O Combustion of ethanol C2H5OH

Some combustion reactions are also combination reactions. 2Mg + O2  2MgO S + O2  SO2