![]() When entropy increases, a certain amount of energy becomes permanently unavailable to do work. Entropy is associated with the unavailability of energy to do work. In the second case, entropy is greater and less work is produced. The same heat transfer into two perfect engines produces different work outputs, because the entropy change differs in the two cases. There is 933 J less work from the same heat transfer in the second process. We noted that for a Carnot cycle, and hence for any reversible processes, We can see how entropy is defined by recalling our discussion of the Carnot engine. That unavailable energy is of interest in thermodynamics, because the field of thermodynamics arose from efforts to convert heat to work. Although all forms of energy are interconvertible, and all can be used to do work, it is not always possible, even in principle, to convert the entire available energy into work. Entropy is a measure of how much energy is not available to do work. Recall that the simple definition of energy is the ability to do work. So the total entropy change for the whole system would be given by the equation Sf Si -Q/Th + Q/Tc, with Si and Sf being the final and initial values of the. The number of available microstates increases when matter becomes more dispersed, such as when a liquid changes into a gas or when a gas is expanded at constant temperature. ![]() ![]() Making Connections: Entropy, Energy, and Work ENE4.A.1 (EK), ENE4.A.2 (EK) Google Classroom About Transcript According to the Boltzmann equation, entropy is a measure of the number of microstates available to a system. Then, (Q2/Q1)min T2/T1When entropy change is zero, a reversible process takes place, because in such a case even the smallest change is sufficient to run the heat engine backward. ![]()
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