# ME103: Thermodynamics

Unit 5: Second Law of Thermodynamics   This unit will introduce the concept of entropy, or the “uncertainty” of a system.  A system’s entropy—along with its temperature—can be used to determine the amount of unusable energy that is present in that system.  (Unusable energy is energy in the form of heat that will be dissipated.)  The higher a system’s entropy, the more irreversible it is considered to be.

The second law of thermodynamics states that the entropy change of an isolated system—whether open or closed—will tend to increase, or at least remain the same.  In other words, this law states that it is impossible for a system to see a decrease in entropy; a system will continue to tend toward irreversibility, at least until it reaches a state of equilibrium.

This unit will take you approximately 30 hours to complete.

☐    Subunit 5.1: 5 hours

☐    Subunit 5.1.1: 1 hour

☐    Subunit 5.1.2: 2 hours

☐    Subunit 5.1.3: 2 hours

☐    Subunit 5.2: 5 hours

☐    Subunit 5.2.1: 2 hours

☐    Subunit 5.2.2: 3 hours

☐    Subunit 5.3: 5 hours

☐    Subunit 5.3.1: 2 hours

☐    Subunit 5.3.2: 3 hours

☐    Subunit 5.4: 15 hours

☐    Subunit 5.4.1: 5 hours

☐    Subunit 5.4.2: 5 hours

☐    Subunit 5.4.3: 5 hours

Unit5 Learning Outcomes
Upon successful completion of this unit, the student will be able to:
- State and illustrate the second law of thermodynamics. - Define entropy. - Calculate entropy for ideal gases, vapors, and saturated fluids, solids, and compressed liquids.

5.1 Introduction to Entropy   - Lecture: MIT OpenCourseWare: Professors Nelson and Bawendi’s Thermodynamics and Kinetics: “Entropy and Irreversibility” Link: MIT OpenCourseWare: Professors Nelson and Bawendi’s Thermodynamics and Kinetics: “Entropy and Irreversibility” (YouTube)

`````` Also available in:
[iTunes
U](http://deimos3.apple.com/WebObjects/Core.woa/Browse/mit.edu.1824849798.01824849803.1817164166?i=1572142822)
(\#10)
Transcript](http://ocw.mit.edu/courses/chemistry/5-60-thermodynamics-kinetics-spring-2008/video-lectures/lecture-10-entropy-and-irreversibility/)

Instructions: Please watch this video (52:44 minutes), which will
introduce you to the concept of entropy.  This lecture covers
subunits 5.1.1-5.1.3.

Thermodynamics & Kinetics, Spring 2008.  (Massachusetts Institute of
Technology: MIT
OpenCourseWare). [http://ocw.mit.edu](http://ocw.mit.edu/ "http://ocw.mit.edu") (accessed
March 11, 2011).  License: Creative Commons
Attribution-Noncommercial-Share Alike.  The original version can be
found [here](http://ocw.mit.edu/courses/chemistry/5-60-thermodynamics-kinetics-spring-2008/video-lectures/lecture-1-state-of-a-system-0th-law-equation-of-state/).

``````

5.1.1 Explanation of Entropy, on the Microscopic Scale   5.1.2 Viewing Entropy Macroscopically   5.1.3 Entropy Relations   5.2 The Second Law of Thermodynamics   - Reading: North Carolina State University: Professor Boles' Lecture Notes on Thermodynamics: “Chapter 5: The Second Law of Thermodynamics” Link: North Carolina State University: Professor Boles’ Lecture Notes on Thermodynamics: “Chapter 5: The Second Law of Thermodynamics” (PDF)

Instructions: Please click on “Study Guide for Chapter 5.”  Please read pages 5–1 to pages 5–22.  Note this reading will cover the material you need to know for subunits 5.2.1 and 5.2.2.

• Lecture: Professor Ramamurti Shankar’s Fundamental of Physics, Yale University: “The Second Law of Thermodynamics and Carnot's Engine” Link: Professor Ramamurti Shankar’s Fundamental of Physics, Yale University: “The Second Law of Thermodynamics and Carnot's Engine” (YouTube)

Also available in:
HTML Transcript, Mp3, Flash, or Quicktime

Instructions: Please watch this video (1:11:10 minutes), which will introduce you to the second law of thermodynamics.  This lecture covers subunits 5.2.1-5.2.2.

Terms of Use: Ramamurti Shankar, Fundamentals of Physics (Yale University: Open Yale Courses), http://oyc.yale.edu (Accessed June 14, 2011).  License: Creative Commons BY-NC-SA 3.0.  The original version can be found here.

5.2.1 Thermodynamic Cycle and Thermal Efficiency   Note: This subunit is covered by the reading assigned beneath subunit 5.2.  Focus on pages 5–2 to 5–5 and 5–7.  Compare the definitions of efficiency for a heat engine and a heat pump.  Work through Example 5.1.  Can the coefficient of performance of a heat pump be greater than 1?

5.2.2 Carnot Cycle   Note: This subunit is also covered by the readings assigned beneath subunits 5.1 and 5.2.  Focus on pages 5–13 to 5–18.  Work through Example 5.2.  Can you estimate the maximum thermal efficiency of a thermal cycle, if you only know the temperatures of the hot and cold reservoirs?

• Assessment: McGraw Hill: Yunus A. Çengel and Michael A. Boles’ Thermodynamics: An Engineering Approach, 4/e: "Multiple Choice Quiz for Chapter 5" Link: McGraw Hill: Yunus A. Çengel and Michael A. Boles’ Thermodynamics: An Engineering Approach, 4/e: "Multiple Choice Quiz for Chapter 5" (HTML)

Instructions: Please click on the link above and answer all 10 questions in the quiz. Select your answer from the choices given for each question. Click on “Submit Answers” at the bottom of the webpage when you have answered all questions. The webpage will tell you whether your answer is correct and what the correct answer is.

5.3 Entropy Generation   - Reading: North Carolina State University: Professor Boles' Lecture Notes on Thermodynamics: “Chapter 6: Entropy” Link: North Carolina State University: Professor Boles’ Lecture Notes on Thermodynamics: “Chapter 6: Entropy” (PDF)

Instructions: Please click on “Study Guide for Chapter 6 Part 1.”  Please read pages 6–1 to pages 6–21.  This reading will define the term “entropy” and discuss entropy changes in reversible and irreversible processes.  You will also learn how to define the second law of thermodynamics in terms of entropy.  Pay attention to the difference between isentropic processes and isothermal processes.

• Lecture: MIT OpenCourseWare: Professors Nelson and Bawendi’s Thermodynamics and Kinetics: “Entropy and the Clausius Inequality” Link: MIT OpenCourseWare: Professors Nelson and Bawendi’s Thermodynamics and Kinetics: “Entropy and the Clausius Inequality” (YouTube)

Also available in:
iTunes U (#9)

Instructions: Please watch this video (50:06 minutes), which will introduce you to entropy generation and the Clausius inequality.  This reading will cover the material you need to know for subunits 5.3.1 and 5.3.2.

Terms of Use: Nelson, Keith A. and Moungi Bawendi.  5.60 Thermodynamics & Kinetics, Spring 2008.  (Massachusetts Institute of Technology: MIT OpenCourseWare). http://ocw.mit.edu (accessed March 11, 2011).  License: Creative Commons Attribution-Noncommercial-Share Alike.  The original version can be found here.

• Lecture: Professor Ramamurti Shankar’s Fundamental of Physics, Yale University: “The Second Law of Thermodynamics (cont.) and Entropy” Link: Professor Ramamurti Shankar’s Fundamental of Physics, Yale University: “The Second Law of Thermodynamics (cont.) and Entropy” (YouTube)

Also available in:
HTML Transcript, Mp3, Flash, or Quicktime

Instructions: Please watch this video (1:11:10 minutes), which will introduce you to how to calculate entropy.  This lecture covers subunits 5.4.1-5.4.3.

Terms of Use:  Ramamurti Shankar, Fundamentals of Physics (Yale University: Open Yale Courses), http://oyc.yale.edu (Accessed June 14, 2011).  License: Creative Commons BY-NC-SA 3.0.  The original version can be found here.

5.3.1 Clausius Inequality   Note: This subunit is covered by the video lecture by Professors Nelsonand Bawendi assigned beneath subunit 5.3.  Please pay attention to the calculation of entropy generation for an ideal Carnot cycle.  How do internal energy and entropy change during an isothermal process and an adiabatic process?

5.3.2 Isentropic process   Note: This subunit is covered by the video lecture by Professors Nelsonand Bawendi assigned beneath subunit 5.3.  Apply the Clausius that you learn about at the end of the video lecture to the feasibility of a perpetual motion machine.

5.4 Calculating Entropy   - Reading: North Carolina State University: Professor Boles’ Lecture Notes on Thermodynamics: “Chapter 6: The Second Law of Thermodynamics” Link: North Carolina State University: Professor Boles’ Lecture Notes on Thermodynamics: “Chapter 6: The Second Law of Thermodynamics” (PDF)

Instructions: Please click on “Study Guide for Chapter 6 Part 1.”  Please read pages 6–22 to pages 6–40.  In this reading, you will learn how to calculate entropy for ideal gases, vapors, and saturated fluids, as well as solids and compressed liquids.  This reading will cover the material you need to know for subunits 5.4.1–5.4.3

5.4.1 Ideal Gases   Note: This subunit is covered by the reading by Professor Bolesassigned beneath subunit 5.4.  The Gibbs equation on page 6–22 is a very powerful equation that allows us to calculate the change in entropy for all systems.  Please read carefully pages 6–30 to 6–35, which show several examples of calculating pressure and temperature of ideal gases during isentropic processes.

5.4.2 Vapors and Saturated Fluids   Note: This subunit is covered by the reading by Professor Boles assigned beneath subunit 5.4.  The Mollier diagram on page 6–24 is very important in designing steam turbines.  Explain why the isobars on the Mollier diagram diverge from each other.

5.4.3 Solids and Compressed Liquids   Note: This subunit is covered by the reading by Professor Bolesassigned beneath subunit 5.4.  Study Example 6.7 on pages 6–36 to 6–40 carefully, which will show you how to calculate entropy changes for solids.

• Assessment: University of South Florida's Dr. Carlos A. Smith’s “Thermodynamics: Homework A – Set 6” Link: University of South Florida's Dr. Carlos A. Smith’s “Thermodynamics: Homework A – Set 6” (PDF)

Instructions: Please attempt all questions in the assessment.  You can find the answers here (PDF).

Terms of Use: This resource is used with the kind permission of Dr. Carlos A. Smith.  To view the original assessment on the University of South Florida's website click here (HTML).

• Assessment: McGraw Hill: Yunus A. Çengel and Michael A. Boles’ Thermodynamics: An Engineering Approach, 4/e: "Multiple Choice Quiz for Chapter 6" Link: McGraw Hill: Yunus A. Çengel and Michael A. Boles’ Thermodynamics: An Engineering Approach, 4/e: "Multiple Choice Quiz for Chapter 6" (HTML)

Instructions: Please click on the link above and answer all 10 questions in the quiz. Select your answer from choices given for each question. Click on “Submit Answers” at the bottom of the webpage when you have answered all the questions. The webpage will tell you whether your answer is correct and what the correct answer is.