This module uses screencasts and an interactive simulation to explain the first law of thermodynamics for a closed system, which means no mass flows into or out of the system. In the examples and simulations, the pistons are assumed to be frictionless. Most of the calculations use absolute temperature, except when calculating a temperature difference, which is the same for kelvin or Celsius. The module 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 the interactive simulation, 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 screencasts that provide an introduction to energy balances and apply the first law to a closed system and answer the questions within the screencasts.
3. Review important equations for closed systems.
4. Use the interactive simulation to further understand the the first law for closed systems.
5. Try to solve the example problems before watching the solutions in the screencasts.
6. Answer the ConcepTests.
7. Look at the list of key points, but only after you try to list the key points yourself.