Pure substance and mixture

• Pure Substance - single kind of matter that cannot be separated into other kinds of matter by any physical means.
• Pure substances: Element and Compound
• John Dalton - Atomic Theory Of Matter
• Atomic Theory Of Matter - All matter is made up of atoms and elements are different types of atoms
• Elements - Only one kind of atom and cannot be broken down into a simple type of matter. Can either exist as atoms or molecules
• 94 naturally occurring elements
• 24 elements produced artificially