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

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

3. 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

4. Elements, Compounds & Molecules

5. 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

6. 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

7. 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.