Describe four classification systems you use at home. Elements are the simplest pure substances. An element cannot be changed into simpler substances by any chemical process. Elements are made up of atoms . All elements listed alphabetically 2.
Compounds are pure substances made up of more than one element.
Atoms of the elements in a compound are chemically bonded together to form molecules . Molecules are changed during chemical reactions. Mixtures consists of two or more substances mixed together but not chemically combined. Substances in mixtures can be separated by physical means. The substances can be present in any amount.