A pure substance can be an ______ or a ______.
Elements and compounds are both examples of pure substances.
Element: A substance that cannot be broken down into chemically simpler components is an element.
Compound: A compound is a pure substance composed of two or more different atoms chemically bonded to one another. A compound can be destroyed by chemical means. It might be broken down into simpler compounds, into their elements, or a combination of the two.
Therefore, A pure substance can be an Element or a Compound.