What does the law of conservation of mass state in chemical reactions?

• A. Mass is neither created nor destroyed; the mass of reactants equals the mass of products.
• B. Mass changes depending on temperature.
• C. Mass is created during reactions.
• D. Mass is destroyed during reactions.

Answer: (A)

In a chemical reaction, matter is rearranged, not created or destroyed. The total amount of mass before the reaction equals the total mass after the reaction, as long as the system is closed. This means the combined mass of all reactants is the same as the combined mass of all products. This idea helps explain why chemical equations are balanced—the same amount of matter is present on both sides.

Temperature can change how matter behaves (like its density or phase), but it does not change the amount of matter. The notion that mass is created or destroyed goes against this principle, which is why those ideas don’t fit.