oxygen combines with a substance and releases energy (heat & light)
CH 4 (g) + 2 O 2 (g) CO 2 (g) + 2 H 2 O (l)
What is the purpose of balancing chemical equations?
The Law of Conservation of Mass states that matter is neither created nor destroyed during a chemical reaction. Therefore, when writing a chemical equation, the reactants must be equal to the products. So you must add any necessary coefficients to show that matter is conserved.