Thermodynamics is often regarded as a universal science that rigorously describes the macroscopic behavior of systems. It is established on a robust theoretical foundation, clear definitions, and with clearly defined boundaries [@Maxwell1878]. It offers a comprehensive framework for analyzing phenomena that classical mechanics alone cannot fully capture$\text{—}$such as relaxation to equilibrium, exothermic and endothermic processes, temperature, phase transitions, and chemical reactions$\text{—}$and for elucidating the interrelationships among various thermodynamic quantities. Its applications extend across multiple fields, encompassing machinery, chemistry, engineering, meteorology, and beyond. Although thermodynamics has a defined scope, there are significant interfaces with other domains of physics, such as statistical mechanics and electromagnetics, which have led to the development of quantum mechanics.

A fundamental assumption in thermodynamics is that the system of interest is surrounded by a sufficiently large external environment surrounding the system of interest, enabling the formulation of the universal laws governing their interactions. Within this context, any interaction, whether through explicit manipulation or exerted effects, that can be precisely inferred from observable macroscopic changes in the surroundings (primarily mechanical interaction) is referred to as work. In contrast, any interactions that are not directly perceived or manipulable are referred to as heat. From the perspective of kinetic theory, however, heat is understood as the motion and mechanical interactions of individual particles, essentially in a form of mechanical work occurring on a microscopic scale. As As Maxwell stated, if we were able to observe all macroscopic molecular motions with the same clarify as the macroscopical changes in large bodies we can perceive, the concept of heat effectively vanishes, and all interactions could be described as work [@Maxwell1878a]. Nevertheless, thermodynamics should be recognized as a rigorous, general theoretical framework that stands independently of our perceptual abilities. It has been firmly established on the basis of extensive theoretical and experimental developments, consistently aligning its fundamental principles with empirical observations [@Tasaki.2000].

Memo

• The role of thermodynamics is to explore universal constraints that the equation of state must satisfy and to establish overarching principles and laws that are independent of the specific properties of any particular equation of state.

• Within the theoretical framework of thermodynamics, the equation of state for a system cannot be determined.

Link

Thermodynamics

Reference

[1] J. C. Maxwell, “Tait’s ‘Thermodynamics,’” Nature, vol. 17, no. 431, pp. 257–259, Jan. 1878, doi: 10.1038/017257a0.

[2] J. C. Maxwell, “Tait’s ‘Thermodynamics’ II,” Nature, vol. 17, no. 432, pp. 278–280, Feb. 1878, doi: 10.1038/017278a0.

[3] 田崎晴明., 熱力学: 現代的な視点から. Tōkyō: 培風館, 2000.