Which statement best describes a mixture?

• A. It is a pure substance
• B. It contains two or more pure substances that retain their identities
• C. It cannot be separated into its components
• D. It has a fixed composition

Answer: (B)

Mixtures are formed when two or more pure substances are combined without forming new chemical bonds, so each component keeps its own identity and properties. The statement that best describes a mixture is that it contains two or more pure substances that retain their identities, because this captures the key idea: the substances are present together but not chemically bound, and you can usually separate them back out by physical methods such as filtering, distilling, or evaporating.

This also explains why the other ideas aren’t correct. A pure substance is one single kind of matter (an element or a compound), not a mixture. A mixture can be separated into its components because the components aren’t chemically fused into a new substance. A mixture does not have a fixed composition; the amounts of each component can vary, unlike a pure substance which has a definite composition.