Final answer:
Zinc, which cannot be changed into a simpler substance by ordinary chemical processes, is classified as an element. It can form compounds such as zinc sulfide when chemically reacted with sulfur, but in its pure form, it maintains its properties as an individual substance.
Step-by-step explanation:
Because zinc can combine with other substances but cannot be changed into a simpler substance by an ordinary chemical process, zinc is classified as an element. Zinc (Zn) is listed on the periodic table and is one of about 118 known elements in the universe. An element, according to the provided reference material, is a substance that cannot be separated into two or more substances by ordinary chemical means and cannot be broken down into chemically simpler components.
For instance, when zinc and sulfur are mixed at room temperature, they form a heterogeneous mixture because no chemical reaction occurs. However, when the mixture is heated, zinc reacts with sulfur to form zinc sulfide (ZnS), a new compound with different properties. Therefore, zinc by itself remains an element, defined by its singular composition and set of properties such as melting point and boiling point.