Sorry for being so formal, but just so that you know you know something classical.īy definition, the change in entropy can be evaluated by measuring the amount of energy transferred. This statement is one of the acceptable statement of second law of thermodynamics. Thus, the driving force for a spontaneous process in an isolated system is an increase in entropy. Such a change is called a spontaneous process. Nature has a tendency for entropy S to increase, and the system changes in response to this tendency. If the change takes place quickly in an irreversible manner, the entropy is greater than what is evaluated, because the temperature increase is not uniform. ![]() However, the changes are supposedly take place slowly over a long period of time, or in an almost equilibrium or reversible condition. You have learned the concept of integration in a calculus course.Įntropy is a state function in that it depends only on the initial and final state of the system, regardless of the path by which the changes take place. This sum can take the form of integration if the temperature various contineously. If the process takes place over a range of temperature, the quantity can be evaluated by adding bits of entropies at various temperatures. Thus, entropy has the units of energy unit per Kelvin, J K -1. When a system receives an amount of energy q at a constant temperature, T, the entropy increase D S is defined by the following equation.Įntropy is the amount of energy transferred divided by the temperature at which the process takes place. Entropy is related to the energy distribution of energy states of a collection of molecules, and this aspect is usually discussed in statistical mechanics. Traditionally, the entropy concept is associated with the second and third laws of thermodynamics. These changes cause an increase in entropy for the system under consideration, but energy is not transferred into or out of the system. A different concept is required to explain spontaneous changes such as the expansion of a gas into an abailable empty space (vacumm) and heat transfer from a hot body into a cold body. Human experienced chemical and physical changes that cannot be explained by energy alone. This concept was developed over a long period of time. Entropy, symbol S, is related to energy, but it a different aspect of energy. We have define energy as the driving force for changes, entropy is also a driving force for physical and chemical changes (reactions). We confine our discussion to thermodynamics (science dealing with heat and changes) and to chemical and physical processes. The word entropy is used in many other places and for many other aspects. You are not alone if you have some difficulty with this concept. Thus, few people understand what entropy really is. ![]() ![]() In terms of measure theory, the differential entropy of a probability measure is the negative relative entropy from that measure to the Lebesgue measure, where the latter is treated as if it were a probability measure, despite being unnormalized.\)Įntropy is a chemical concept that is very difficult to explain, because a one-sentence definition will not lead to a comprehensive statement. Differential entropy (described here) is commonly encountered in the literature, but it is a limiting case of the LDDP, and one that loses its fundamental association with discrete entropy. : 181–218 The actual continuous version of discrete entropy is the limiting density of discrete points (LDDP). Unfortunately, Shannon did not derive this formula, and rather just assumed it was the correct continuous analogue of discrete entropy, but it is not. Differential entropy (also referred to as continuous entropy) is a concept in information theory that began as an attempt by Claude Shannon to extend the idea of (Shannon) entropy, a measure of average (surprisal) of a random variable, to continuous probability distributions.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |