# Introduction to Entropy

Before this chapter, we had only used the

#### 2nd Law

to help us analyze#### thermodynamic cycles

.The overall goal is to find a way to analyze an individual process that will help us evaluate a real process by comparing its performance to the performance of a

#### reversible process

.In the previous lesson, we used the

#### 2nd Law

(in the form of the#### 2nd Carnot Principle

) for the first time in the analysis of a single process. In this analysis, we discovered a new#### property

#### or

state variable that turns out to be every bit as important and useful as internal energy and enthalpy.In this lesson, we give our new property a name:

## entropy

. Entropy will enable us to apply the#### 2nd Law

to processes and to quantitatively assess and compare their performance.Once we have defined

#### entropy

, we will spend the rest of the lesson learning how to find, use and interpret#### entropy

data in both tabular form (NIST WebBook) and in graphical form (phase diagrams).© B-Cubed, 2003, 2005, 2006, 2014. All rights reserved.

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