If we assume that the substance is a perfect crystal at zero degrees when it is not, our theory predicts a value for the absolute entropy at higher temperatures that is too small, because it does not include the term \(S. By expanding consideration of entropy changes to include the surroundings, we may reach a significant conclusion regarding the relation between this property and spontaneity. In Chapter 11, we discuss the use of the third law to determine the absolute entropy of substances at ordinary temperatures. This principle is the basis of the Third law of thermodynamics, which states that the entropy of a perfectly-ordered solid at 0 K is zero. Processes that involve an increase in entropy of the system (Δ S > 0) are very often spontaneous however, examples to the contrary are plentiful. The 3rd law of thermodynamics says that a perfect (100 pure) crystalline structure at absolute zero (0 K) will have no entropy ((S)). In other words, as the absolute temperature of a substance approaches zero, so does its entropy. If the ground state is degenerate (i.e. If the ground state is non-degenerate, then the entropy approaches zero. In the quest to identify a property that may reliably predict the spontaneity of a process, we have identified a very promising candidate: entropy. The 3rd law of thermodynamics states that as the temperature of a system approaches zero, then the entropy of the system approaches zero or some positive constant. Calculate entropy changes for phase transitions and chemical reactions under standard conditions.State and explain the second and third laws of thermodynamics.By the end of this section, you will be able to:
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