FIXME-Delete this page Navigate back to the activity

Is Work Done on or by the System?: Instructor's Guide

Main Ideas

  • First and Second Thermodynamic Laws
  • Determining the system and surroundings

Students' Task

Estimated Time: 10 minutes

In small groups, students are asked to decide if work is being done on or by the system in several scenarios.

Prerequisite Knowledge

  • Familiarity with the first and second thermodynamic laws.


Activity: Introduction

A brief lecture on work in thermodynamics in the context of the first thermodynamic law will help give students some tools for completing the worksheet. Students are then placed in small groups and given the handout for this activity and asked to decide if work is done on or by the system for each scenario.

Activity: Student Conversations

A lot of the challenge in these questions revolve around the definition of system–figuring out where the energy goes is critical in understanding whether work has been done.

In addition, students must invoke the definition of work in terms of force and displacement, in order to establish who is working on whom.

Activity: Wrap-up

For each scenario (if time permits), ask a group to state their answer and why. Ask the other groups if they agree with the first group's answer; if the second group does not agree with the first group's answer, have them reason why their answer is correct. After covering all of the scenarios, be sure to note that deciding what is considered the system and what is considered the surrounding is very important in finding what is doing work or what is having work done upon it.


Personal Tools