Such tiny systems are outside the domain of thermodynamics, but they can be investigated using statistical mechanics. But on scales of a few atoms, the second law does not apply for example, in a system of two molecules, it is possible for the slower-moving ("cold") molecule to transfer energy to the faster-moving ("hot") molecule. No violation of the second law of thermodynamics has ever been observed in a macroscopic system. Thermodynamics is a theory of macroscopic systems at equilibrium and therefore the second law applies only to macroscopic systems with well-defined temperatures. Thus, a heat engine with 100% efficiency is thermodynamically impossible. At least some of the energy must be passed on to heat a low-temperature energy sink. That is, it is impossible to extract energy by heat from a high-temperature energy source and then convert all of the energy into work. It is impossible to convert heat completely into work. For example, the electrical energy going into a refrigerator is converted to heat and goes out the back, representing a net increase in entropy.Ī third formulation of the second law, the heat engine formulation, by Lord Kelvin, is: This is allowable in a non-isolated system, however only if entropy is created elsewhere, such that the total entropy is constant or increasing, as required by the second law. Note that from the mathematical definition of entropy, a process in which heat flows from cold to hot has decreasing entropy. For example in a refrigerator, heat flows from cold to hot, but only when electrical energy is added. Informally, "Heat doesn't flow from cold to hot (without work input)", which is obviously true from everyday experience. Heat cannot spontaneously flow from a material at lower temperature to a material at higher temperature. If a system is at equilibrium, by definition no spontaneous processes occur, and therefore the system is at maximum entropy.Īlso due to Clausius is the simplest formulation of the second law, the heat formulation: (An exception to this rule is a reversible or "isentropic" process, such as frictionless adiabatic compression.) Processes that decrease total entropy of an isolated system do not occur. Thus, the system can either stay the same, or undergo some physical process that increases entropy. In an isolated system, a process can occur only if it increases the total entropy of the system. The formulation of the second law that refers to entropy directly is due to Rudolf Clausius: Thus, the theorems of thermodynamics can be proved using any form of the second law. There are many ways of stating the second law of thermodynamics, but all are equivalent in the sense that each form of the second law logically implies every other form (Fermi, 1936). 5.1 Perpetual motion of the second kind.
![second law of thermodynamics evolution argument second law of thermodynamics evolution argument](https://media.springernature.com/lw685/springer-static/image/art%3A10.1007%2Fs12052-009-0195-3/MediaObjects/12052_2009_195_Fig1_HTML.gif)
SECOND LAW OF THERMODYNAMICS EVOLUTION ARGUMENT FREE
4.1 Special cases: Gibbs and Helmholtz free energies.There are many versions of the second law, but they all have the same effect, which is to explain the phenomenon of irreversibility in nature.
![second law of thermodynamics evolution argument second law of thermodynamics evolution argument](https://unapologeticsorg.files.wordpress.com/2020/02/img_0457.jpg)
Entropy is a measure of how far along this evening-out process has progressed. In simple terms, the second law is an expression of the fact that over time, ignoring the effects of self-gravity, differences in temperature, pressure, and density tend to even out in a physical system that is isolated from the outside world.
![second law of thermodynamics evolution argument second law of thermodynamics evolution argument](https://www.askamathematician.com/wp-content/uploads/2013/03/4571122942_2f08440e28_b.jpg)
The second law traces its origin to French physicist Sadi Carnot's 1824 paper Reflections on the Motive Power of Fire, which presented the view that motive power (work) is due to the fall of caloric ( heat) from a hot to cold body ( working substance). The second law of thermodynamics is an expression of the universal law of increasing entropy, stating that the entropy of an isolated system which is not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium.