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 over time, regardless of the processes occurring within the system. This principle is foundational in chemistry and physics, indicating that mass is neither created nor destroyed in chemical reactions or physical changes. For example, when substances react, the mass of the reactants is equal to the mass of the products, highlighting the balance and continuity of matter.

This understanding is crucial for various scientific calculations and experiments—ensuring that when reactions take place, the accounted masses before and after the reaction align perfectly, affirming the integrity of the law.