"One simple statement of the law is that heat always moves from hotter objects to colder objects (or 'downhill'), unless energy in some form is supplied to reverse the direction of heat flow."
Introduction and interpretation of the second law of thermodynamics, including directionality and irreversibility of processes and entropy.
Concepts of thermodynamics: The basic concepts and definitions of thermodynamics, including the zeroth, first, and second laws.
Heat and work: The concepts of heat and work, their relationship to each other, and how they are measured.
Energy transfer: The different methods of energy transfer, including conduction, convection, and radiation.
Entropy: The concept of entropy and how it relates to the second law of thermodynamics.
Carnot cycle: The Carnot cycle, a theoretical thermodynamic cycle that is used to describe the maximum efficiency of an engine.
Heat engines and refrigerators: The thermodynamic principles that govern heat engines, refrigerators, and heat pumps.
Irreversibility: The concept of an irreversible process and how it relates to the second law of thermodynamics.
Thermal reservoirs: The concept of a thermal reservoir and how it is used in thermodynamics.
Kelvin-Planck statement: The Kelvin-Planck statement, which describes the impossibility of a heat engine that continuously produces work in a cyclical process.
Clausius statement: The Clausius statement, which describes the impossibility of a heat engine that transfers heat from a cooler body to a hotter body without any outside work being done.
Maximum entropy principle: The maximum entropy principle, which states that in an isolated system, the entropy will tend to increase over time until it reaches a maximum.
Statistical mechanics: The principles of statistical mechanics, which is used to describe the behavior of large groups of particles.
The Boltzmann equation: The Boltzmann equation, which relates the entropy of a system to the number of microstates available to it.
The Gibbs free energy: The Gibbs free energy, which describes the maximum amount of work that can be extracted from a system at constant temperature and pressure.
The principle of minimum entropy production: The principle of minimum entropy production, which states that the system will tend to evolve in a way that minimizes the production of entropy.
There is only one Second Law of Thermodynamics, which states that the total entropy of a closed system cannot decrease over time: This law applies to all physical systems, not just thermodynamic systems, and is a fundamental principle of nature. The law can be expressed in several different ways, such as:.
The Clausius statement: Heat cannot spontaneously transfer from a colder body to a hotter body.
The Kelvin-Planck statement: It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a hotter body to a colder body.
The Gibbs statement: The chemical potential of any substance in a closed system at equilibrium has a minimum value.
All of these statements describe different aspects of the Second Law of Thermodynamics, but they all ultimately lead to the same conclusion: The total entropy of a system always increases.
"Not all heat energy can be converted into work in a cyclic process."
"The second law of thermodynamics in other versions establishes the concept of entropy as a physical property of a thermodynamic system."
"It can be used to predict whether processes are forbidden despite obeying the requirement of conservation of energy as expressed in the first law of thermodynamics and provides necessary criteria for spontaneous processes."
"The entropy of isolated systems left to spontaneous evolution cannot decrease, as they always arrive at a state of thermodynamic equilibrium where the entropy is highest at the given internal energy."
"An increase in the combined entropy of the system and surroundings accounts for the irreversibility of natural processes."
"The second law was an empirical finding that was accepted as an axiom of thermodynamic theory."
"Statistical mechanics provides a microscopic explanation of the law in terms of probability distributions of the states of large assemblies of atoms or molecules."
"The first formulation, which preceded the proper definition of entropy and was based on caloric theory, is Carnot's theorem, formulated by the French scientist Sadi Carnot."
"Carnot's theorem, formulated by the French scientist Sadi Carnot, who in 1824 showed that the efficiency of conversion of heat to work in a heat engine has an upper limit."
"The first rigorous definition of the second law based on the concept of entropy came from German scientist Rudolf Clausius in the 1850s."
"Heat can never pass from a colder to a warmer body without some other change, connected therewith, occurring at the same time."
"The second law of thermodynamics allows the definition of the concept of thermodynamic temperature."
"The concept of thermodynamic temperature relies also on the zeroth law of thermodynamics."
"The second law of thermodynamics provides necessary criteria for spontaneous processes."
"The second law of thermodynamics in other versions establishes the concept of entropy as a physical property of a thermodynamic system."
"Heat always moves from hotter objects to colder objects (or 'downhill'), unless energy in some form is supplied to reverse the direction of heat flow."
"Not all heat energy can be converted into work in a cyclic process."
"The increase in the combined entropy of system and surroundings accounts for the irreversibility of natural processes."
"The entropy of isolated systems left to spontaneous evolution cannot decrease."