Is Work Done on or by the System?
Highlights of the activity
- This small group activity is designed to give students practice in determining if work is being done on or by a system and further practice on identifying what is part of a system and what is part of its surroundings.
- Students use their knowledge of thermodynamics to determine if work is being done or by a system in each given physical situation and identify which parts of each scenario are parts of a system and which parts are its surroundings.
- The whole class discussion focuses on ensuring that students have good reasons for their answers and correcting students with wrong answers.
Reasons to spend class time on the activity
In thermodynamic processes, students can find it challenging to determine what is defined as the system and what are the surroundings. Also, since the sign of the work term can change depending on the physical situation, it can be difficult to determine if the system is doing work or not. This activity allows students to practice determining these aspects of a physical system, and also gives teachers an exercise to conclude with tips on analyzing the work done in a physical scenario.