A chemical is any substance consisting of matter. This includes any liquid, solid, or gas. A chemical is any pure substance (an element) or any mixture (a solution, compound, or gas). They can either occur naturally or can be created artificially. A chemical is an element or any combination of these elements. For example, oxygen in the air is a chemical, and is always a combination of two oxygen elements. ... Water, a combination of two hydrogen atoms bonded to an oxygen atom, is a chemical