Which law states matter cannot be created or destroyed?

• A. Law of Conservation of Energy
• B. Second Law of Thermodynamics
• C. Law of Entropy
• D. Law of Conservation of Mass

Answer: (D)

Matter cannot be created or destroyed in ordinary chemical processes. The law of conservation of mass states that the total mass of the substances going into a chemical reaction equals the total mass of the substances that come out. In other words, mass is rearranged but not lost or gained. For example, when you burn hydrogen with oxygen to form water, the mass of the hydrogen and oxygen you started with equals the mass of the water produced.

This principle is most directly about matter, so it’s distinct from the law of conservation of energy, which is about energy itself rather than mass. The second law of thermodynamics concerns entropy and the natural direction of processes, not mass balance. While in nuclear reactions a tiny amount of mass can convert to energy (and vice versa) due to E=mc², in typical chemistry and everyday contexts mass conservation is the standard approach.