(noun) A chemical is a either a chemical element or a material with a defined composition of such elements: a chemical compound. (see also molecule). The term is often used to refer to bulk material, rather than to individual microscopic or submicroscopic particles, e.g., "A chemical is a specific collection of atoms or molecules."
(noun) Chemicals is the industry or trade of producing or manipulating such chemicals.
... volume, the Parana[?] with its impressive Iguaçu[?] falls, the Rio Negro, São Francisco[?], Xingu, Madeira and the Tapajós[?] rivers.
Situated along the equator, ...