What does the law of conservation of mass state?

The law of conservation of mass states that in a closed system, the total mass remains constant, meaning mass cannot be created or destroyed during a chemical reaction. This fundamental principle is crucial in understanding chemical processes, as it implies that the mass of the reactants before a reaction must equal the mass of the products after the reaction. This principle is foundational to both chemistry and physics and helps in balancing chemical equations, where each side must represent the same amount of matter.

This law emphasizes that while matter can change forms—such as from solid to liquid or from reactants to products—the total mass involved in those transformations does not change. Thus, it reinforces the idea that even when substances undergo chemical changes, their total mass remains the same. This conservation of mass ensures that all molecules and atoms are accounted for in any reaction, aligning with the principles observed in experimental settings.