Two concurrently published papers detail the results of a long-term US-based study revealing students' challenges with the ideal gas law and misconceptions about microscopic processes. These identified misconceptions guided university course enhancements over several years. 

Evidence-based suggestions

• To be able to apply concepts from mechanics properly to thermal physics, students need a stronger command of that material than most acquire during a typical introductory course (at ages 16-18). A thorough review of the relevant mechanics can promote a better understanding of the behaviour of gases.

Findings about learners’ ideas

The papers report a large number of misconceptions. Those related to thermal physics and energy include:

• Many students have difficulties distinguishing between the ideas of ‘temperature’ and ‘heat’ and using these terms appropriately.
• Many students use the term ‘heat’ to mean both the additional energy of an object at a higher temperature (compared to the same object at a lower temperature) and the energy that is transferred spontaneously from a hotter to a colder object because of the temperature difference.
• There were references to heat as a state rather than a process.
• Some students assume that molecular collisions generate kinetic energy.
• There was confusion between heat, temperature and internal energy, leading to the idea that temperature cannot change in an adiabatic process.
• For samples of different gas with the same volume and at the same temperature, the size, structure and mass of the gas particles require different values for the pressure or number of molecules.
• Students may misapply the conservation of momentum for particles in an ideal gas. For example, some learners do not distinguish between energy and momentum.
• Students assume that lower or greater particle density implies lower or greater temperature in an ideal gas.
• The ideal gas law (as opposed to the first law of thermodynamics) predicts the change in temperature of a gas being worked on (or work being done by a gas).
• The pressure of an ideal gas is always directly proportional to its Kelvin temperature.
• Thermal insulation implies a constant temperature even if other changes are made to the system. Thermal insulation actively counteracts any temperature changes in a system.

Further suggestions

• Try an iterative process of instructional-based sessions in which assessment plays a vital role. Each topic in a course should include a pre-test, worksheet, homework and post-test.
• Laboratory experiments on the ideal gas law during which research-based instructional strategies should be undertaken. Students should make quantitative measurements of the variables of the gas laws to then respond to qualitative questions on the interpretation and application of the concepts at a macroscopic level.

Study Structure

Aims

To explore the misunderstandings that students have about the gas law to inform the university's curriculum.

Evidence collection

Evidence was collected over several years from pre and post-instruction tests as part of the course. A comparison of the post-instruction tests with the results of students who had not received the instructional tutorials was made and responses were analysed to identify misconceptions to inform further improvements of tutorial materials.

Details of the sample

The participants in the study included over 1000 students at the undergraduate level (aged 17-19). These were science and engineering majors enrolled in introductory algebra or calculus-based physics courses at several universities. Most had taken or were concurrently taking introductory chemistry.