In a closed system, which statement about mass is true?

In a closed system, which statement about mass is true?

• A. Mass is not conserved.
• B. Mass is conserved due to energy alone.
• C. Mass can disappear in a chemical change.
• D. In a closed system, the total mass remains the same because atoms are neither created nor destroyed.

Answer: (D)

Mass conservation in chemical changes means the total amount of matter doesn’t change because the same atoms are present before and after, just rearranged. In a closed system, nothing enters or leaves, so the total mass stays fixed. Atoms aren’t created or destroyed during chemical changes; they’re simply bonded differently, so the sum of their masses remains the same. Energy exchanges with the surroundings don’t change this basic count of atoms, and the tiny mass changes predicted by mass–energy equivalence are negligible for ordinary chemistry. That’s why the statement that the total mass remains the same because atoms are neither created nor destroyed is the correct one. The others misstate what stays constant or rely on energy accounting in a way that isn’t applicable here.

Mass conservation in chemical changes means the total amount of matter doesn’t change because the same atoms are present before and after, just rearranged. In a closed system, nothing enters or leaves, so the total mass stays fixed. Atoms aren’t created or destroyed during chemical changes; they’re simply bonded differently, so the sum of their masses remains the same. Energy exchanges with the surroundings don’t change this basic count of atoms, and the tiny mass changes predicted by mass–energy equivalence are negligible for ordinary chemistry. That’s why the statement that the total mass remains the same because atoms are neither created nor destroyed is the correct one. The others misstate what stays constant or rely on energy accounting in a way that isn’t applicable here.