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CHEM105: Physical Chemistry I

Unit 3: Application of the First Law of Thermodynamics   In the third unit of this course, you will learn about measuring thermodynamic properties for reactions and exploring the fundamentals of how heat engines operate. Steam engines, internal combustion engines, diesel engines, jet engines, and rocket engines are all heat engines, as are refrigerators and heat pumps. In ideal cycle analysis, the operations of these engines will be treated as thermodynamic cycles, and you will use the first law of thermodynamics to calculate their cycle efficiency and work output. While such methods overlook effects that happen in non-ideal systems, this basic approach can be adapted to treat more realistic engines. Moreover, you can use thermodynamic cycles (Hess’s law) to arrive at values for thermodynamic state changes that cannot easily be measured by using the actual path the reaction takes. Such state changes can be computed by using cycles involving quantities that you can measure along different paths. 

Unit 3 Time Advisory
Completing this unit should take approximately 11 hours.

☐  Subunit 3.1: 6 hours
☐  Subunit 3.2: 1 hour
☐  Subunit 3.3: 1 hour
☐  Subunit 3.4: 1 hour
☐  Subunit 3.5: 2 hours

Unit3 Learning Outcomes
Upon successful completion of this unit, you should be able to: - define calorimetry; - calculate the enthalpy of reaction and the enthalpy of formation of compounds; - state and use Hess’s law; - describe various heat engines and their principles of operation; - define the Carnot cycle and Carnot efficiency; - define the Otto cycle, and describe its relationship to the internal combustion engine; and - describe how refrigerators and heat pumps work.

3.1 Calorimetry: Measuring the Enthalpy   - Lecture: The Massachusetts Institute of Technology OpenCourseWare: Dr. Moungi Bawendi and Dr. Keith Nelson’s “Lecture 7: Calorimetry” Link: The Massachusetts Institute of Technology OpenCourseWare: Dr. Moungi Bawendi and Dr. Keith Nelson’s “Lecture 7: Calorimetry”

 Also available in:  

[iTunesU](http://ocw.mit.edu/courses/chemistry/5-60-thermodynamics-kinetics-spring-2008/video-lectures/lecture-7-calorimetry/)  

[MP4](http://ocw.mit.edu/courses/chemistry/5-60-thermodynamics-kinetics-spring-2008/video-lectures/lecture-7-calorimetry/)  

 Instructions: Watch the video (approximately 55 minutes long) to
see how one uses calorimetry to obtain the enthalpy of the formation
of compounds and the enthalpy of reactions. In fact, many
thermochemical parameters can be measured in a calorimeter. In
situations in which you cannot measure enthalpy directly, Hess’s law
allows you to use a thermodynamic cycle (taking a different path) to
find it. 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: The University of Windsor: Introductory Physical Chemistry: Dr. Rob Schurko’s Course Notes: “Lecture 8: Thermochemistry” Link: The University of Windsor: Introductory Physical Chemistry: Dr. Rob Schurko’s Course Notes: “Lecture 8: Thermochemistry” (PDF)

    Instructions: Read the notes. Note that these notes have been assigned previously in this course; as you read this time, focus on the detailed description of how the enthalpy changes that accompany chemical processes are defined and measured, and how the acquired enthalpy data may be analyzed within the context of the first law of thermodynamics. Also be sure to work through all the examples provided in the reading.

    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: Dr. David Ronis’s “Thermochemistry” Link: McGill University: Dr. David Ronis’s “Thermochemistry” (PDF)

    Instructions: Read Dr. Ronis’s lecture notes on thermochemistry. This reading focuses on enthalpy changes that accompany chemical reactions. Read through the notes and work through all the illustrations and examples presented in the reading.

    Reading this material should take approximately 3 hours.

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

3.2 Heat Engines   - Web Media: Georgia State University: Dr. Rod Nave’s “Heat Engine Concepts” Link: Georgia State University: Dr. Rod Nave’s “Heat Engine Concepts” (HTML)

 Instructions: Review the chart on the webpage to explore the
concept of heat engines. Explore the links on this webpage to see
some practical engines based on thermodynamic cycles. Focus on
getting a sense of these engines and how they work. You will revisit
them in more detail in Unit 4 of this course, at which point you
will perform calculations with them.  

 Completing this web media assignment should take approximately 1
hour.  

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

3.3 The Carnot Cycle   - Web Media: Georgia State University: Dr. Rod Nave’s “Carnot Cycle” Link: Georgia State University: Dr. Rod Nave’s “Carnot Cycle” (HTML)

 Instructions: Read the webpage, which discusses the most efficient
thermodynamic engine possible. It is based on a cycle with two
isothermal and two adiabatic paths. Using the embedded formula on
the webpage, you can input two temperatures to obtain the Carnot
efficiency for that engine. Are you surprised by what you see?  

 Completing this web media assignment should take approximately 1
hour.  

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

3.4 The Otto Cycle (Internal Combustion)   - Web Media: Georgia State University: Dr. Rod Nave’s “The Otto Cycle” Link: Georgia State University: Dr. Rod Nave’s “The Otto Cycle” (HTML)

 Instructions: Click on the link and read the section titled “Step
through engine cycle” to view a short web schematic that shows you
how a car’s engine works. Continue clicking on the “Step through
engine cycle” link in order to view each part of the schematic,
paying special attention to the path taken around the cycle.  


 Completing this web media assignment should take approximately 1
hour.  

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

 

3.5 Refrigerators and Heat Pumps   - Reading: Georgia State University: Dr. Rod Nave’s “Refrigerator” and “Heat Pump” Link: Georgia State University: Dr. Rod Nave’s “Refrigerator”and “Heat Pump” (HTML)

 Instructions: Read the two sections titled “Refrigerator” and “Heat
Pump” to learn about heat flow from a hotter to a colder region and
how refrigerators and heat pumps work. Also take time to read the
“Coefficient of Performance” section on the “Heat Pumps” webpage.
Work through each of the calculations illustrated in these sections
and make sure you understand how the calculations are set up and
executed.  

 Reading this material should take approximately 2 hours.  

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