Carbon and hydrogen are pure substances. Each of each is made of only one type of atom, but carbon atoms are different from hydrogen atoms, carbon and hydrogen, chemically combined for a form of methane

Answer 1

that is a compound. A pure substance is a substance that cannot be separated into simpler substances by physical means. Carbon and hydrogen are both considered pure substances because they are made up of only one type of atom. However, when carbon and hydrogen atoms chemically combine to form methane (CH4), it becomes a compound. A compound is a substance composed of two or more elements chemically bonded together in a fixed ratio. In the case of methane, it is composed of one carbon atom bonded to four hydrogen atoms.