Which statement best describes the Law of Conservation of Mass during physical and chemical changes?

• A. Matter can be created or destroyed during chemical reactions.
• B. The mass of products is always greater than the mass of reactants in a chemical reaction.
• C. Physical changes always result in a loss of mass.
• D. The total mass of substances remains unchanged before and after a physical or chemical change.

Answer: (D)

Verified step by step guidance

1. Understand that the Law of Conservation of Mass states that mass cannot be created or destroyed in an isolated system during any physical or chemical change.
2. Recognize that during chemical reactions, atoms are rearranged but the total number of atoms—and thus the total mass—remains constant.
3. Note that physical changes, such as changes in state (solid, liquid, gas), do not alter the chemical identity or the total mass of the substance.
4. Evaluate each statement by comparing it to the principle that total mass remains constant before and after any change.
5. Conclude that the statement 'The total mass of substances remains unchanged before and after a physical or chemical change' correctly describes the Law of Conservation of Mass.