Which statement best describes an alloy?

• A. A metallic substance composed of two or more elements.
• B. Pure iron with carbon.
• C. A compound of a metal and nonmetal with fixed stoichiometry.
• D. An impurity-laden crystal without changing properties.

Answer: (A)

An alloy is a metallic substance formed by blending two or more elements, usually with at least one metal, to tailor properties such as strength or hardness. The proportions can vary and the mixture creates a material with characteristics different from the constituent elements. Classic examples include steel (iron with carbon and other elements), bronze (copper with tin), and brass (c copper with zinc).

This description best captures what an alloy is. The other ideas describe materials that aren’t alloys: a chemical compound has a fixed ratio of elements, an impurity-laden crystal is not defined as an alloy, and while adding carbon to iron produces steel, the broad, inclusive definition focusing on two or more elements is the most accurate way to describe an alloy.