What does the Law of Conservation of Matter state?

• A. Matter can be created in chemical reactions
• B. Matter can be destroyed in a chemical reaction
• C. Energy is conserved but matter is not
• D. Matter is conserved; atoms are rearranged but not created or destroyed

Answer: (D)

The main idea being tested is that matter is conserved in chemical reactions. In these processes, atoms are rearranged to form new substances, but the total amount of matter stays the same in a closed system. That means the total number and type of atoms before a reaction equal the total after the reaction, just connected in different ways. So the best statement is that matter is conserved; atoms are rearranged but not created or destroyed. This helps explain why, in a sealed container, the mass before and after a reaction remains the same—even though the substances involved look different. The other ideas—matter being created or destroyed, or only energy being conserved—don’t fit with what we observe in ordinary chemical changes.