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CHEM105: Physical Chemistry I

Unit 2: The First Law of Thermodynamics   The first law of thermodynamics states, simply, that energy is conserved. While energy can be changed from one form to another—say, by converting chemical energy into heat by burning a candle and then converting that heat into mechanical work by heating a gas within a balloon—energy cannot be gained or lost once all transfers and conversions of energy are accounted for.

Unit 2 Time Advisory
Completing this unit should take approximately 12 hours.

☐  Subunit 2.1: 9 hours

☐  Subunit 2.2: 1 hour

☐  Subunit 2.3: 2 hours

Unit2 Learning Outcomes
Upon successful completion of this unit, you should be able to: - define U, the internal energy, and describe its relationship to expansion work; - define H, the enthalpy, and describe how it relates to P, V, and U within a system; - describe state changes of a gas by using various types of paths; - define isobaric, adiabatic, and isothermal changes as well as the thermodynamic cycle; - perform calculations with ideal gases undergoing state changes along various paths; and - describe the relationship between thermodynamic cycles and work.

2.1 Internal Energy and Expansion Work   - Lecture: The Massachusetts Institute of Technology OpenCourseWare: Dr. Robert Field, Dr. Moungi Bawendi, and Dr. Keith Nelson’s “Lecture 3: Internal Energy, Expansion Work” Link: The Massachusetts Institute of Technology OpenCourseWare: Dr. Robert Field, Dr. Moungi Bawendi, and Dr. Keith Nelson’s “Lecture 3: Internal Energy, Expansion Work”

 Also available in:  

[iTunesU](http://ocw.mit.edu/courses/chemistry/5-60-thermodynamics-kinetics-spring-2008/video-lectures/lecture-3-internal-energy-expansion-work/)  

[MP4](http://ocw.mit.edu/courses/chemistry/5-60-thermodynamics-kinetics-spring-2008/video-lectures/lecture-3-internal-energy-expansion-work/)  

 Instructions: Watch the video (approximately 52 minutes long), in
which you will further explore the concept of heat capacity, which
was introduced in Unit 1 of this course. You also will learn more
about the first law of thermodynamics, discover how gases can do
work under different conditions, and see how to maximize the work
that gases can do. You will also learn about an important state
function: U, the internal energy. You can find the lecture notes for
this video here(PDF).  

 Watching this lecture should take approximately 1 hour.  

 Terms of Use: This resource is licensed under a [Creative Commons
Attribution-NonCommercial-ShareAlike 3.0 United States
license](http://creativecommons.org/licenses/by-nc-sa/3.0/us/).
  • Reading: Dr. Howard DeVoe’s Thermodynamics and Chemistry (2nd ed.): “Chapter 3: The First Law” Link: Dr. Howard DeVoe’s Thermodynamics and Chemistry (2nd ed.): “Chapter 3: The First Law”(PDF)

    Instructions: Read chapter 3, beginning on page 56. Note that you already have encountered this chapter earlier in this course; this time, re-read itfor an overview of the first law of thermodynamics. Be sure to work through the details of each section in the chapter, paying special attention to the mathematical formulation of first law properties. You should also work through the problems at the end of chapter 3 to gauge your understanding of the material in this chapter.

    Reading this material and completing the problems should take approximately 3 hours.
     
    Terms of Use: This resource is licensed under a Creative Commons Attribution-NonCommercial-NoDervis 3.0 Unported License.
     

  • Reading: McGill University: Dr. David Ronis’s “Notes on the First Law of Thermodynamics Chemistry 223” Link: McGill University: Dr. David Ronis’s “Notes on the First Law of Thermodynamics Chemistry 223” (PDF)

    Instructions: Read these notes. This reading offers particularly clear illustrations of mechanical work and the differences between reversible and irreversible (or spontaneous) thermodynamic processes. At this point in the course, you should be able to work through the derivations of all the equations presented in the reading and feel comfortable with the underlying differential, multivariate calculus. If you are still struggling with the mathematical aspects of thermodynamics, you may find it useful to read these notes again. The mathematical formulations and manipulations found in Dr. Ronis’s notes are presented with special care and clarity.

    Reading this material should take approximately 2 hours.

    Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

  • Reading: The University of Windsor: Introductory Physical Chemistry: Dr. Rob Schurko’s Course Notes: “Lecture 9: The First Law: Machinery” Link: The University of Windsor: Introductory Physical Chemistry: Dr. Rob Schurko’s Course Notes: “Lecture 9: The First Law: Machinery” (PDF)

    Instructions: Read the course material. Be sure to carefully review all the sketches.

    Reading this material should takeapproximately 3 hours.

    Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

  • Optional: The University of Notre Dame OpenCourseWare: Dr. Joseph M. Powers’s Lecture Notes on Thermodynamics: “Chapter 5: The First Law of Thermodynamics” Link: The University of Notre Dame OpenCourseWare: Dr. Joseph M. Powers’s Lecture Notes on Thermodynamics: “Chapter 5: The First Law of Thermodynamics” (PDF)

    Instructions: Note that this reading is optional and primarily intended for enrichment and review purposes. If you choose to complete this reading, compare the material presented in these lecture notes with the concepts you have explored in the previous assignments in this subunit.

    Terms of Use: This resource is licensed under a Creative Commons Attribution 2.5 Generic license.

2.2 Enthalpy   - Lecture: The Massachusetts Institute of Technology OpenCourseWare: Dr. Moungi Bawendi and Dr. Keith Nelson’s “Lecture 4: Enthalpy” Link: The Massachusetts Institute of Technology OpenCourseWare: Dr. Moungi Bawendi and Dr. Keith Nelson’s “Lecture 4: Enthalpy”

 Also available in:  

[iTunesU](http://ocw.mit.edu/courses/chemistry/5-60-thermodynamics-kinetics-spring-2008/video-lectures/lecture-4-enthalpy/)  

[MP4](http://ocw.mit.edu/courses/chemistry/5-60-thermodynamics-kinetics-spring-2008/video-lectures/lecture-4-enthalpy/)  

 Instructions: Watch the video (approximately 55 minutes in length)
to learn about the important state function enthalpy, H, which
allows you to know the heat flow into or out of a system. ΔH = Δ(U +
PV) = q<sub>p</sub>. You also will explore the dependence of the
enthalpy on P and V as well as look at the Joule-Thompson
experiment. You can find the lecture notes for this video here
(PDF).  

 Watching this lecture should take approximately 1 hour.  

 Terms of Use: This resource is licensed under a [Creative Commons
Attribution-NonCommercial-ShareAlike 3.0 United States
license](http://creativecommons.org/licenses/by-nc-sa/3.0/us/).

2.3 Thermodynamics of Adiabatic Processes   - Lecture: The Massachusetts Institute of Technology OpenCourseWare: Dr. Moungi Bawendi and Dr. Keith Nelson’s “Lecture 5: Adiabatic Changes” and “Lecture 6: Thermochemistry” Link: The Massachusetts Institute of Technology OpenCourseWare: Dr. Moungi Bawendi and Dr. Keith Nelson’s “Lecture 5: Adiabatic Changes” and “Lecture 6: Thermochemistry”

 Also available in:  
 [iTunesU (Lecture
5)](http://ocw.mit.edu/courses/chemistry/5-60-thermodynamics-kinetics-spring-2008/video-lectures/lecture-5-adiabatic-changes/)  
 [MP4 (Lecture
5)](http://ocw.mit.edu/courses/chemistry/5-60-thermodynamics-kinetics-spring-2008/video-lectures/lecture-5-adiabatic-changes/)  
 [  
 iTunesU (Lecture
6)](http://ocw.mit.edu/courses/chemistry/5-60-thermodynamics-kinetics-spring-2008/video-lectures/lecture-6-thermochemistry/)  
 [MP4 (Lecture
6)](http://ocw.mit.edu/courses/chemistry/5-60-thermodynamics-kinetics-spring-2008/video-lectures/lecture-6-thermochemistry/)  

 Instructions: Watch the two videos (approximately 50 minutes and 52
minutes in length, respectively) to learn about changes of state
that occur for ideal gases undergoing various thermodynamic
processes along, for example, isothermal, isobaric, and adiabatic
paths. This discussion leads us to the topic of thermodynamic
cycles, which we can exploit to do work. In these videos you also
will explore the topic of entropy and see the first application of
thermodynamic principles and analysis to non-gaseous systems. You
can find the lecture notes for “Lecture 5: Adiabatic Changes” here
(PDF) and those for “Lecture 6: Thermochemistry” here (PDF).  

 Watching this lecture should take approximately 2 hours.  

 Terms of Use: This resource is licensed under a [Creative Commons
Attribution-NonCommercial-ShareAlike 3.0 United States
license](http://creativecommons.org/licenses/by-nc-sa/3.0/us/).