In matter, the term heterogeneous may be applied to which of the following?

• A. Mixtures, but not elements or compounds.
• B. Elements, but not compounds.
• C. Compounds, but not elements.
• D. Compounds and elements, but not mixtures.

Answer: (A)

Heterogeneous means not uniform in composition throughout a sample, so you can see different parts or regions with different properties. This describes mixtures that are not evenly mixed, like gravel in sand, salad, or oil droplets in water. Elements and compounds are pure substances with uniform composition everywhere within them: an element is one kind of atom, and a compound has a fixed ratio of elements that is the same in every sample. Because of that uniformity, neither elements nor compounds are described as heterogeneous. Therefore, heterogeneous applies to mixtures, while elements and compounds are not.