A substance might be pure with a single compound or impure with impurities along with principal compounds.
pure substance, propanone
Pure substance
it is a pure substance.... not
Cyclohexane (or cyclohexanone, if that is what you meant) is usually found as a pure substance, and is produced industrially as such. It consists of a single molecule. However, cyclohexane can be impure if it is tainted or something is added to it.
Methane is a pure substance.
pure substance
pure substance
Pure Substance
A pure substance is classified by having a definite and constant composition. The substance can be either an element or a compound, but what makes the substance pure, is that it does not vary.
Neon is a pure substance. Elements and compounds are pure substances; mixtures are not.
CH3COOH is a pure substance. It is the chemical formula for acetic acid.
Refined substance can be a pure substance depending on the type of sugar used. If the refined sugar is white, then it is a pure substance. If it the refined sugar is brown, then it is not a pure substance.