Question

a chemist is studying an unknown substance and could break the substance into its elemental components only by using chemical means. based on this observation, how should the unknown substance be classified? impure substance solution mixture pure substance

Explanation:

1. Recall the definitions:

• A pure substance (element or compound) can only be broken into its elemental components by chemical means (like a compound, which is a pure substance made of two or more elements chemically bonded, and needs chemical reactions to decompose into elements).
• Mixtures (including impure substances, solutions) can be separated into components by physical means (like filtration, distillation, etc.).

1. The observation states the substance is broken into elements only by chemical means. So it must be a pure substance (since mixtures are separated physically). The other options (impure substance, solution, mixture) are all mixtures (or types of mixtures) and are separated by physical methods, not chemical.

Answer:

D. pure substance