Students classify as elements, compounds, or mixtures common materials such as water, copper, lead, brass, naturally occurring metal ores, salt, sugar, chocolate chip cookies, coffee, tea, and iced tea. Build and display molecular models of various elements, compounds, and mixtures for students to identify and classify. Students should recognize that molecules have no electrical charge. Once students have had practice working with these models, have them work in small groups to build their own models and test each other. Students should track their success in classifying the substances.
Students brainstorm practical applications of methods of separation.
Discuss the method used in each case. When students build ball and stick models, circulate as they work, providing input and suggestions, and asking questions to check their understanding. Assess their models for completeness and accuracy. Have students classify models of various substances as mixtures, compounds, or elements and predict characteristics such as phase changes. Ask students to identify given samples as elements, compounds, or mixtures based on their observations of the properties.