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. Check their classifications for accuracy.
Students devise an experimental procedure to separate the compounds of a given mixture.
Check their procedure for evidence that they understand terms and definitions, and for the logic of their procedure.