Of all the conceivable ideal-gas processes, almost all introductory physics textbooks as well as more advanced texts on thermodynamics emphasize only four: isochoric, isobaric, isothermal, and adiabatic (isentropic). These are processes in which a state variable--volume, pressure, temperature, or entropy--remains constant. It turns out that these…

Historically, classical thermodynamics was developed during attempts to improve the efficiency of steam engines. Those investigations led to the well-known zeroth, first, and second laws of thermodynamics. Although these laws are presented independently, linkages between the zeroth and second laws have been pointed out in the physics teaching…

Breathing is something we all do, usually without thinking about it. But when viewed through the lens of physics, respiration becomes an example of elementary thermodynamics. As shown here, the lungs can be modeled as a two-stroke heat engine. Breathing thereby provides a novel physics application for life science students, demonstrating the…

With the rapid spread of high-speed railway technology, there is a resurgence of interest in trains and railways. The main propulsive engine for railways was the steam engine for over a century, which gave way to the diesel and electrical engines. The steam engine was crucial to the birth and development of the railway industry, and understanding…

Physics and chemistry students learn several methods to determine the density of materials. While measuring the mass of materials is usually simple, volume measurements are more complex. For simple shapes the volume may be determined by measuring its geometry; for more complex shapes students often use Archimedes' principle. However, neither of…

When we teach thermodynamics, a vacuum container used to keep food isolated from air is a cheap and interesting teaching device. There are some experiments already described in the literature and we can also find videos of demonstrations on YouTube. At the same time, there is increasing interest in how to utilize smartphones in physics…

Two bodies initially at different temperatures gathered into an isolated container exchange heat and reach an equilibrium state with a common final temperature. During the process, the system is out of equilibrium and its intermediate temperature is not well defined. By conceiving a quasi-static process with infinitesimal steps from the initial to…

An attempt to calibrate a conventional oven led to making a measurement of a thermophysical property of water using items found in the author's home. Specifically, the ratio of the energy required to heat water from the melting point to boiling to the energy required to completely boil away the water is found to be 5.7. This may be compared to the…

Project-based learning has been shown to be an effective pedagogical strategy that motivates students and thus promotes learning. In this article we describe a project-based unit centered on the physics of solar cookers (Fig. 1 and 3). Our goal was to elevate the solar cooker from a summer camp activity to a college-level project that could be…

The possibility of negative temperatures on the Kelvin scale is intriguing and confusing simultaneously. This is because students are used to thinking of temperature as a measure of the internal energy of a system. While this concept is good for many systems, it does not work for all systems. Nuclear and electron spin systems, along with lasers…

Two students in a recent thermodynamics/statistical mechanics course needed to complete a course-related project to receive honors credit for the class. Such courses are typically theoretical, without an accompanying laboratory, although there are existing related hands-on exercises. The choice of the project was influenced by one student's desire…

In the last decade, a powerful tool has been given to physics teachers to visualize thermodynamic phenomena. Thermal imaging cameras are fascinating devices opening the world of (even small) temperature changes and being able to uncover hidden manifestations of many processes around us. This paper describes a few qualitative thermal imaging…

While entropy is often described as "disorder," it is better thought of as a measure of how spread out energy is within a system. To illustrate this interpretation of entropy to introductory college or high school students, several activities have been created. Students first study the relationship between microstates and macrostates to…

It is well known that heat transfer between two objects results in a positive change in the total entropy of the two-object system. The second law of thermodynamics states that the entropy change of a naturally irreversible process is positive. In other words, if the entropy change of any process is positive, it can be inferred that such a process…

The second law of thermodynamics has various formulations. There is the "Clausius formulation," which can be stated in a very intuitive way: "No process is possible whose sole result is the transfer of heat from a cooler to a hotter body." There is also the "Kelvin-Plank principle," which states that "no cyclic…