Elements of classical thermodynamics

Abstract

Systems, properties, and states in thermodynamics A system is the part of the universe we are interested in. The rest of the universe is called surroundings. The system volume, V , is well defined and the system boundary is clearly identified with a surface. Systems are described by their mass M and energy E . Instead of using mass M , a system may be defined by the number of moles, N/N A , where N is the number of molecules and N A is Avogadro's number. There are three kinds of system in thermodynamics: Isolated systems . In these systems, there is no mass or energy exchange with the surroundings. Closed systems . In these systems, there is no mass exchange with the surroundings. Energy can flow between the system and the surroundings as heat, Q , or work, W . Heat is the transfer of energy as a result of a temperature difference. Work is the transfer of energy by any other mechanism. Open systems . In these systems, mass and energy may be exchanged with the surroundings. A thermodynamic state is a macroscopic condition of a system prescribed by specific values of thermodynamic properties.