The law of conservation of mass states that (a) matter is neither created nor destroyed. (b) the mass of an object remains the same even if chemical change occurs (c) the number of molecules before and after a chemical reaction cannot change. (d) mass is lost when a chemical change occurs.

Step 1: Define the Problem

Identify the correct statement that aligns with the law of conservation of mass.

Step 2: Break Down the Problem

Evaluate each option to determine which one accurately reflects the principle of the law of conservation of mass.

Step 3: Apply Relevant Concepts

The law of conservation of mass states that in a closed system, mass is conserved during a chemical reaction. This means that the total mass of reactants equals the total mass of products.

Step 4: Analysis, Verify and Summarize

• Option (a): "Matter is neither created nor destroyed" aligns with the law of conservation of mass.
• Option (b): "The mass of an object remains the same even if chemical change occurs" is also consistent with the law.
• Option (c): "The number of molecules before and after a chemical reaction cannot change" is incorrect because the number of molecules can change, but the total mass remains constant.
• Option (d): "Mass is lost when a chemical change occurs" contradicts the law of conservation of mass.

Final Answer

(a) matter is neither created nor destroyed.