What does the Law of Conservation of Mass state?

The Law of Conservation of Mass states that mass cannot be created or destroyed in a chemical reaction or physical process. This principle indicates that the total mass of substances involved in a reaction remains constant, meaning that the mass of the reactants will equal the mass of the products, no matter the form they take. This foundational concept in chemistry is essential for understanding chemical reactions and processes, as it underpins the idea that atoms are simply rearranged rather than being annihilated or created anew during such reactions.

For context, the other options do not accurately reflect the Law of Conservation of Mass. The notion of energy changing forms pertains to the Law of Conservation of Energy, which is a separate concept. Similarly, while energy can remain constant in a closed system, this does not apply to mass specifically. Lastly, the idea that mass can only be merged or divided does not capture the essence of conservation, which emphasizes the unchanging total mass rather than suggesting that mass can only undergo specific types of alterations.