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How does the equation for methane combustion show conservation of mass?

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combustion
chemical reaction Log burning in a fire. Burning wood is an example of a chemical reaction in which wood in the presence of heat and oxygen is transformed into carbon dioxide, water vapor, and ash.

The combustion of methane (CH₄) demonstrates the law of conservation of mass because the total number of atoms for each element remains identical on both sides of the chemical equation:

CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l)

In this balanced equation, there is one carbon atom, four hydrogen atoms, and four oxygen atoms on both the reactant and product sides. Because matter is neither created nor destroyed during a chemical reaction, the total mass of the reactants must equal the total mass of the products.12

For example, 16 grams of methane and 64 grams of oxygen react to produce 44 grams of carbon dioxide and 36 grams of water. Consequently, 80 grams of reactants yield exactly 80 grams of products, confirming that mass is conserved. The stoichiometric factors (the coefficients 1 and 2) ensure that the ratio of molecules accounts for every atom, maintaining this balance.1