There are two kinds of pure substances: elements and compoundsElements are made up of only one type of atom. Examples are copper, aluminum, and hydrogen. All the elements discovered thus far are shown in a periodic table.
Compounds are made of two or more elements or atoms. Examples are water, hydrogen peroxide and table sugar. The ratio of the elements in a given compound is fixed. For example, the ratio of hydrogen to oxygen in water is 2 atoms of hydrogen to 1 atom of oxygen. In hydrogen peroxide, hydrogen and oxygen are also combined, but the ratio is 2 atoms of hydrogen to 2 atoms of oxygen. Water and hydrogen peroxide are different compounds with different properties.
Classification of Matter Rhodora Snow Ph.D.
Definition of Matter Has mass and occupies space Examples Water Wood Plastic
Classification of Matter Pure Substances Fixed Composition Mixtures Variable Composition Howdoyouturnthison. A plate of dolly mixture. 29 July 2008. http://commons.wikimedia.org/wiki/File:Dolly_mixture.JPG
Benjah-bmm27, Hydrogen peroxide. 5 May 2007. http://commons.wikimedia.org/wiki/File:Hydrogen-peroxide-3D-vdW.png
Elements and Compounds Compounds may be separated into its component elements. Example Electrolysis of water General Chemistry students of University of Siegen [photographer], Public Domain, http://upload.wikimedia.org/wikipedia/commons/7/78/Elektrolyse1.jpg