This module uses screencasts and interactive simulations to explain the lever rule, which is a way to determine the amount of each phase when two phases are in equilibrium. It results from a mass balance. The module then provides example problems to allow the user to test themselves. Your retention of material in this module will increase if you write down reasons for your answers to ConcepTests, questions in screencasts, and questions to answer before using interactive simulations, and you try to solve the example problems before watching the screencast solutions. We suggest using the learning resources in the following order:

1. Attempt to answer the multiple-choice ConcepTest and solve the example problem before watching the screencasts or working with the simulations.
2. Watch the screencast that describes the lever rule.
3. Review important equations for the lever rule.
4. Use the interactive simulation(s) to further understand the use of the lever rule with phase diagrams.
5. Try to solve the example problems before watching the solutions in the screencasts.
6. Answer the ConcepTest.
7. Look at the list of key points, but only after you try to list the key points yourself.