ASVAB (Armed Services Vocational Aptitude Battery)General Science (GS)Easy
A student is observing a chemical reaction in a sealed container. They notice that the total mass of the reactants before the reaction is exactly equal to the total mass of the products after the reaction. This observation best illustrates which fundamental scientific law?
- ALaw of Conservation of Mass
- BLaw of Definite Proportions
- CLaw of Conservation of Energy
- DLaw of Multiple Proportions
Show answer & explanationAnswer & explanation
Correct answer: A. Law of Conservation of Mass
The observation that the total mass before and after a chemical reaction remains constant is the direct definition of the Law of Conservation of Mass. This law states that matter cannot be created or destroyed in an isolated system.
Why the other options are wrong
- B. The Law of Definite Proportions states that a chemical compound always contains the same elements in the same proportions by mass, regardless of the source.
- C. The Law of Conservation of Energy states that energy cannot be created or destroyed, but it does not directly address mass in a chemical reaction.
- D. The Law of Multiple Proportions states that when two elements form more than one compound, the ratios of the masses of the second element that combine with a fixed mass of the first element are small whole numbers.
Law of Conservation of Mass
States that mass in an isolated system is neither created nor destroyed by chemical reactions or physical transformations. The total mass of reactants equals the total mass of products.
- Applies to chemical reactions and physical changes.
- Matter cannot be created or destroyed.
- Total mass remains constant.
Memory trick: Many Laws Govern Chemistry's Core Principles.