So hopefully this starts to give you a sense of what entropy is. Entropy entropy s is a thermodynamic state function which can be described qualitatively as a measure of the amount of disorder present in a system. Entropy and the second law of thermodynamics the conservation of energy law allows energy to flow bidirectionally between its various forms. Also, what does robert frosts poetry have to do with entropy.
Entropy is the basic thermodynamic variable that serves to define and relate most thermal properties of matter, and the equilibrium state for an isolated system. These two formulas are the center of chemical thermodynamics, and if you do not remember them or where they came from, go back and look. Lecture notes thermodynamics of materials materials. Entropy and the second law of thermodynamics the second law of thermodynamics in thermochemistry we have seen that reactions are infl uenced by the comparative enthalpies of reactants and products. From a chemical perspective, we usually mean molecular disorder. For example in a pendulum, energy continually goes tofrom kinetic energy and potential energy. Dgdhtds and dg0rtlnk and that is a very good thing. And you might say okay this is all fun intellectual discussion, whats the big deal.
Nonequilibrium thermodynamics 10 second law of thermodynamics and entropy reversibility and the second law figure 10. Second law of thermodynamics and entropy video khan. The second law of thermodynamics introduces the notion of entropy s, a measure of system disorder messiness u is the quantity of a systems energy, s is the quality of a systems energy. S only depends on the initial and final equilibrium states not the path. As we learn in the second law of thermodynamics, the entropy in the universe is constantly increasing. Some of this material is quite challenging, be sure to read this material carefully. These lecture notes are intended for students who already have some notions in ther. Laws of thermodynamics 2nd law of thermodynamics william rankine, 1850s assert that energy has quality and quantity and actual processes occur in the direction of decreasing quality of energy entropy source at high temp sink at low temp heat engine q in q out w find potential work. The lecture handouts are available in the table below. Laws of thermodynamics apply only when a system is in equilibrium or moves from one equilibrium state to another equilibrium state. Thermodynamics is not concerned about how and at what rate these energy transformations are carried out, but is based on initial and final states of a system undergoing the change. These are lecture notes for ame 20231, thermodynamics. The focus of the lecture is the concept of entropy. Willard gibbs in the 1870s, and the informationtheoretic entropy, usually expressed as h, of claude shannon and ralph hartley developed in the 1940s.
Thermodynamics ii lectures entropy and second law of thermodynamics donate here. Entropy and disorder entropy is a measure of disorder. Spontaneous endothermic reactions do occur and that means that there must be another factor than enthalpy involved. Bookmark file pdf chemical engineering thermodynamics lecture notes. Suppose you have a gas that is expanding and moving a piston from left to right, thus doing useful, i. Specific examples are given to calculate the entropy change for a number of different processes. Lectures on entropy and free energy lecture 1 after a formal course on thermodynamics most chemistry or biochemistry students remember two formulas. Boltzmanns microscopic formula for entropy is introduced and used to explain irreversibility. Lecture notes section contains the class notes files.
At the time when carnot lived, the first law of thermodynamics, the conservation of energy, was not known. Pdf lecture notes on thermodynamics carlos martinez. Lecture videos, lots of examples, and quizzes with solutions teach the info you need. Entropy is a measure of energy that is no longer available to perform useful work within the current environment. This articles include thermodynamics systemclosed, open, isolated system with example and control volume, pdf. Reconciling thermodynamic and state definitions of entropy.
Entropy in thermodynamics and information theory wikipedia. Entropy, free energy, and the direction of chemical reactions 20. Thermodynamics systemclosed, open, isolated system with. Lectures on entropy and free energy brandeis university. If you mix two compounds together will they react spontaneously. The joint system of a system and its environment is called universe. Find materials for this course in the pages linked along the left. This section includes extremely refined notes for every lecture given in the course. Transfer of heat from the system to its environment is spontaneous if entropy production is positive, requiring that the system has a higher temperature. Freely browse and use ocw materials at your own pace.
The entropy is extensive if and only if there is a. The results of thermodynamics are all contained implicitly in certain apparently simple statements called the laws of thermodynamics. No process is possible in which the sole result is the absorption of heat from a reservoir and its complete conversion into work. A measure of disorder entropy and the clausius inequality the second law of thermodynamics leads to the definition of a new property called entropy, a quantitative measure of microscopic disorder for a system. Total energy conservation, viz the first law of thermodynamics, dictates that. Heat engines, entropy, and the second law of thermodynamics. Phys 200 lecture 24 the second law of thermodynamics. His aim was to express both laws in a quantitative fashion. Entropy michael fowler 71008 introduction the word entropy is sometimes used in everyday life as a synonym for chaos, for example. The overall change of the internal energy u hence vanishes. And, i put an exclamation mark here, because it seems like a very profound statement. But the big deal is that to some degree you can describe the universe in terms of entropy. There are close parallels between the mathematical expressions for the thermodynamic entropy, usually denoted by s, of a physical system in the statistical thermodynamics established by ludwig boltzmann and j.
It is a science, and more importantly an engineering tool, that is. Describes processes that involve changes in temperature, transformation of energy, relationships between heat and work. Energy accountability in the science of thermodynamics is described through the. Also, what does robert frosts poetry have to do with entropy, and how can you prepare toothpaste for an elephant. Entropy and 2nd law of thermodynamics monday, january 30 chem 102h t. The second law leads to the definition of a new property called entropy. In this pictorial representation, the system is shown qualitatively with an original enthalpy and entropy. Thermodynamics online is the course to end your struggles in thermo. Online thermodynamics course engineering courses online. Voiceover the second law of thermodynamics, one statement of it is that the entropy of the universe only increases. A reaction or change of state is said to be spontaneous if it is. Chapter 4 entropy and the second law of thermodynamics. Class 11 chapter 6 thermodynamics 10 what is entropy.
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