Pure Substance A single type of material that has a definite composition Can be an element, molecule or compound

Atoms The smallest unit of matter Atoms of different substances have different characteristics

Mixture Two or more substances that have been joined together but not chemically combined Mixtures are NOT considered pure substances Can be separated by simple, physical means Examples: salad, Kool-aid, nachos

Elements, Compounds & Molecules

Element A pure substance made up of one type of atom that cannot be broken down Each element can be identified by the type of atom it is made of Examples: Gold, Carbon, Iron

Molecule Two or more elements that have been chemically combined Molecules can be made by combining the same atom or different atoms Examples: Molecule made from more than one type of atom Molecule made from one type of atom

Compound Two or more different atoms that have been chemically combined When different atoms combine to form a compound, the properties are different than the properties of the atoms/elements that make it up. Example: Chlorine is a yellow, toxic gas. Sodium is a white, reactive metal. But sodium chloride is neither toxic nor reactive.