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Why is the total mass of products equal to the total mass of reactants?

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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 total mass of products is equal to the total mass of reactants because of the law of conservation of mass, which dictates that matter is neither created nor destroyed during chemical reactions.123

In any chemical process, atoms are simply rearranged into new combinations to form different molecules; they are not created, destroyed, or transformed into other elements. Because the same number and types of atoms are present on both sides of a balanced chemical equation, the total mass remains constant.234

This principle, often associated with the work of Antoine Lavoisier, serves as a fundamental foundation of modern chemistry. It allows chemists to use stoichiometry to calculate the precise mass relationships between reactants and products, ensuring that the mass of the substances entering a reaction is exactly accounted for in the substances produced.12