This US-based study examined undergraduate students' difficulties in understanding thermal physics, specifically the first law of thermodynamics. The aim was to identify misconceptions and areas of misunderstanding to inform improved teaching approaches.

Evidence-based suggestions

• Students will gain greater understanding when instructed to use diagrams (in particular P-V diagrams) to explain or reiterate their answers as this often leads to students recognizing errors.
• The researchers also recommend that learners alternate between diagrammatic and verbal explanations of their answers.

Learners’ ideas

• Some students believed that, in some scenarios, the pressure’s the only part of the PV = nRT equation which affects the kinetic energy.
• Students have an overgeneralization of the concept of state function. In thermal physics, quantities (such as heat transfer and work) are not state functions.
• Students show a tendency to treat the concept of work as superfluous, as unconnected to temperature changes in gases, or on the other hand, as being essentially synonymous with heat.
• A proportion of students (19%)  explicitly argued that work was independent of the path.
• Strong support for the idea that heat is process-independent was consistent in student samples.
• Students tended to identify heat with internal energy, as well as a widespread inability to correctly identify heat as a ‘‘process quantity’’ instead of a ‘‘state quantity”.
• The data consistently showed that no more than about one in five students emerged from the introductory physics course with an adequate grasp of the first law of thermodynamics.
• Students’ everyday familiarity with terms tends to lead them in precisely the wrong conceptual direction.

Further suggestions

• Solidifying the learner's understanding of "work done" in a mechanics context before teaching how it differs in thermodynamics.
• Instructors or written questions often make use of very common idealizations (e.g., the idea of a thermal reservoir) - learners should have these notions articulated to them before attempting to solve the problem at hand or be asked to articulate them themselves.

Study Structure

Aims

The study was designed to determine student difficulties in understanding thermal physics (particularly the 1st and 2nd Laws of Thermodynamics) and attempting to devise alternative instructional approaches.

Evidence collection

Evidence for the study was collected via three methods as the students completed their course. These methods were used at different times on different groups of students.

• Students completed a written free-response quiz as part of their thermodynamics course.
• Students completed a multiple-choice question, also as part of their course.
• Selected students were interviewed as they took part in a problem-solving exercise based on thermodynamics. The interviews lasted 1 hour or more, during which time the students completed a set of thermodynamics-based questions developed for this study.

Outcomes of the test and interview questions were analysed using simple techniques (percentage of correct responses) to identify areas of confusion or misconceptions held by the students.

Details of the sample

The study sample consisted of undergraduate students enrolled on a "calculus-based introductory general physics course", predominantly engineering majors, across several cohorts in different years (1999-2002). The age range spans 18-22 years old.  The sample was based on convenience (willing participants in the course). Three assessments took place:

• The written free response quiz cohort contained 653 students.
• The multiple-choice questionnaire cohort contained 407 students.
• Interviews were carried out with 32 undergraduates.