Which of the following best explains why the law of conservation of mass should be studied in a closed system?

• A. Because only open systems can show that mass is conserved during chemical reactions.
• B. Because a closed system allows gases to escape, which demonstrates mass loss during reactions.
• C. To prevent energy from being transferred into or out of the system, which affects mass measurements.
• D. To ensure that no matter enters or leaves the system, allowing accurate measurement of mass before and after a chemical reaction.

Answer: (D)

Verified step by step guidance

1. Understand the law of conservation of mass: it states that mass cannot be created or destroyed in a chemical reaction, so the total mass of reactants equals the total mass of products.
2. Recognize the importance of a closed system: a closed system does not allow matter to enter or leave, which means the total mass inside remains constant throughout the reaction.
3. Consider what happens in an open system: matter, such as gases, can escape or enter, making it difficult to measure the true mass change and verify the conservation of mass.
4. Realize that studying the law in a closed system ensures that any changes in mass measurements are due only to the chemical reaction itself, not due to loss or gain of matter from the surroundings.
5. Therefore, the law of conservation of mass should be studied in a closed system to ensure accurate and reliable mass measurements before and after the reaction, confirming that mass is conserved.