the process whereby heavy molecules of naphtha or petroleum are broken down into hydrocarbons of lower molecular weight (especially in the oil-refinin more..the process whereby heavy molecules of naphtha or petroleum are broken down into hydrocarbons of lower molecular weight (especially in the oil-refining process)(noun.process)
break partially but keep its integrity(verb.change)
the science of matter; the branch of the natural sciences dealing with the composition of substances and their properties and reactions (noun.cognition)