4. Classification of Pure Substances 1. Made of one type of atom. (Some elements are found as multi-atom molecules in nature.) 2. Combine together to make compounds. 1. Made of one type of molecule, or array of ions. 2. Molecules contain 2 or more different kinds of atoms. Elements Compounds
5. Classification of Mixtures 1. Made of multiple substances, but appears to be one substance. 2. All portions of a sample have the same composition and properties. 1. Made of multiple substances, whose presence can be seen. 2. Portions of a sample have different composition and properties. Heterogeneous Homogeneous
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