Thermodynamics Equations Thermodynamics Equations Thermodynamics is expressed by a mathematical framework of thermodynamic equations which relate various thermodynamic quantities and physical properties measured in a laboratory or production process. Thermodynamics is based on a fundamental set of postulates, that became the laws of thermodynamics. One of the fundamental thermodynamic equations is the description of thermodynamic work in analogy to mechanical work, or weight lifted through an elevation against gravity, as defined in 1824 by French physicist Sadi Carnot. Carnot used the phrase motive power for work. In the footnotes to his famous On the Motive Power of Fire, he states: “We use here the expression motive power to express the useful effect that a motor is capable of producing. This effect can always be likened to the elevation of a weight to a certain height. It has, as we know, as a measure, the product of the weight multiplied by the height to which it is raised.� With the inclusion of a unit of time in Carnot's definition, one arrives at the modern definition for power:
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Thermodynamics is sometimes called energetics. Thermodynamics is based on three fundamental laws. They are applicable to all the phenomena in nature. These laws are not based on any theory but are based on experimental facts. The laws have been subjected to rigorous mathematical treatment and have yielded correlations between different observable properties of matter. These have been proved to be very convenient and useful in describing the states of system in chemical and physical transformations. The result of thermodynamic deductions have been proved to be correct by experiments and found to be rigidly valid. Thermodynamics is, therefore an exact science.Thermodynamics has a great predicting power. It can predict whether a given process will occur spontaneously or not under a given set of conditions. The laws provide necessary criteria for predicting the feasibility of a process. However, it gives no information with regard to the rate at which a given change will proceed. Thermodynamics deals only with the states of the system and makes no mention of the mechanism of how the change is accomplished.Thermodynamics answers why a change occurs but not how it occurs. Classical thermodynamics is based on the behavior of bulk or macroscopic properties of the system, i.e., systems having many molecules and is independent of the atomic and molecular structure. Consequently, no information can be obtained regarding the molecular structure. This difficulty is however obviated in statistical thermodynamics where the laws of mechanics are applied to the behavior of individual molecules and then a suitable average is taken. The results obtained from complementary to each other.
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History of Thermodynamics :- From the time of stone age humans knew about the Thermodynamics. The knowledge of friction of dry wood with one another producing fire, cooling of air when air is blown through a small opening in lips and cooling of the surroundings when hail stones melt to become water and burning of some inflammable material resulting in release of heat are some of the earlier observations related to thermodynamics. 1. The first idea of thermodynamics was established by Fourier, Kelvin, Gibbs, and Carnot amongst others. 2. Thermodynamics began in 1822 with Fourier’s publication of the theorie analytique wherein it is derived that the partial differential equation for the temperature distribution in a rigid body. 3. Sadi Carnot a couple of years later put down further the foundations of thermodynamics with his renowned memoir about steam power. He perceived that steam power was a motor of industrial revolution that would prompt economical and social life. 4. The caloric, a notion introduced by Lavoisier was to identify heat was further worked upon by James P Joule who identified it as a form of energy transferring by showing experimentally that heat and work are mutually convertible. 5. This was the birth of concept of energy and the basis of formulation of the first law of thermodynamics. Fundamentals of Thermodynamics:- Matter tends to be at rest. To attain this state substances change their state so that they can be with minimum internal energy. In this process the excess energy is given as heat. Some times the substances which are with minimum internal energy get activated by supply of energy in the form of heat. The study of these energy changes is the fundamental feature of Thermodynamics. Thermodynamics is not based on hypothetical laws but is experimentally determined. Generally, the values are taken at 1 atmosphere pressure and room temperature taken as 298K.
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