Final answer:
The combustion of propane and methane are chemical reactions that release heat and produce carbon dioxide and water. Propane's combustion is represented by a balanced chemical equation involving sufficient oxygen, while methane, prevalent in natural gas, combusts easily releasing significant heat energy.
Step-by-step explanation:
The flame hazard classes of various fuels relate to the specific dangers associated with their combustion. When balancing a combustion equation, one must ensure a proper stoichiometric ratio of reactants to products is achieved. For propane (C3H8), the balanced equation for complete combustion is C3H8(l) + 5O2(g) → 3CO2(g) + 4H2O(l), demonstrating the production of carbon dioxide and water upon combustion.
Methane (CH4) burns easily, which is one reason it's used widely as a natural gas fuel. Its combustion is represented by the equation CH4(g) + 2O2(g) → CO2(g) + 2H2O(l), releasing large amounts of heat energy. Such combustion reactions are exothermic, releasing energy that can be quite intense, depending on the hydrocarbon.