# ME103: Thermodynamics

Unit 2: Properties of Pure Substances   The simplest thermodynamic situations involve “pure substances.”  Pure substances are single, uncontaminated substances that have not been mixed with any other substances.  They are fundamental building blocks (atoms or molecules) arranged in a certain way.  Common pure substances include water, molecular nitrogen, graphite, diamond.  We also often have a situation in which it is convenient to treat a mixture as a single substance (e.g air in combustion problems, impure water, gasoline).  You must understand how to carry out pure substance calculations prior to analyzing mixtures (this latter subject will be addressed in future courses).

This unit will take you approximately 31 hours to complete.

☐    Subunit 2.1: 4 hours

☐    Subunit 2.2: 6 hours

☐    Subunit 2.2.1: 2 hours

☐    Subunit 2.2.2: 2 hours

☐    Subunit 2.2.3: 2 hours

☐    Subunit 2.3: 12 hours

☐    Subunit 2.3.1: 3 hours

☐    Subunit 2.3.2: 3 hours

☐    Subunit 2.3.3: 3 hours

☐    Subunit 2.3.3: 3 hours

☐    Subunit 2.4: 1 hour

☐    Subunit 2.5: 8 hours

☐    Subunit 2.5.1: 4 hours

☐    Subunit 2.5.2: 4 hours

Unit2 Learning Outcomes
Upon successful completion of this unit, the student will be able to:
- Identify intensive and extensive properties. - Use the liquid-vapor tables to calculate properties of a pure substance as functions of pressure, temperature, and specific volume. - Compute properties of ideal gases using ideal gas law. - Compute properties of real gases using compressibility factor. - Compute properties of saturated vapor-liquid mixture using quality.

2.1 Intensive and Extensive Properties   - Reading: McGraw Hill: Yunus A. Çengel and Michael A. Boles’ Thermodynamics: An Engineering Approach, 4/e: “Student Study Guide PPTs” Link: McGraw Hill: Yunus A. Çengel and Michael A. Boles’ Thermodynamics: An Engineering Approach, 4/e: "Student Study Guide PPTs" (PPT)

Instructions: Please click on “Chapter 01 - Student Study Guide (399.0K)” to download the PPT slides. In these notes, you will be introduced to intensive and extensive properties of a system and will learn how to identify whether a property of a system is extensive or intensive.  There are some properties that depend on the size of a system, while other properties are independent of the size of the system.  Is volume an extensive property or an intensive property?

2.2 Pure Substances   - Reading: North Carolina State University: Professor Boles’ Lecture Notes on Thermodynamics: “Chapter 2: Properties of Pure Substances” Link: North Carolina State University: Professor Boles’ Lecture Notes on Thermodynamics: “Chapter 2: Properties of Pure Substances” (PDF)

Instructions: Please click on “Study Guide for Chapter 2.”  Please read pages 2–1 to pages 2–8 only.  In this reading, you will be introduced to phase changes and the P-V-T surface of pure substances.  What are the phases of a pure substance?  Make sure that you understand the definitions of critical state, phases, and triple point.

2.2.1 Phase Changes   Note: This subunit is partially covered by the reading assigned beneath subunit 2.2 (North Carolina State University: Professor Boles’ Lecture Notes on Thermodynamics: “Chapter 2: Properties of Pure Substances”).  Follow the description of the process of heating water from room temperature to superheated vapor on pages 3–6.  Trace the transitions between different states of water on Figure 2-11.

• Reading: University of Notre Dame: Professor J. M. Powers’ Lecture Notes on Thermodynamics: “Chapter 3: Properties of Pure Substances” Link: University of Notre Dame: Professor J. M. Powers’ Lecture Notes on Thermodynamics: “Chapter 1: Introduction to Thermodynamics” (PDF)

Instructions: Please read section 3.2 (pages 41–46).  The reading will introduce you to phase diagram of a pure substance.

2.2.2 P-V-T Charts   Note: This subunit is covered by the reading assigned beneath subunit 2.2 (North Carolina State University: Professor Boles’ Lecture Notes on Thermodynamics: “Chapter 2: Properties of Pure Substances”).  Pay attention to the P-V-T charts on page 2.  The P-v-T chart is the most convenient way to represent the properties of a pure substance.

2.2.3 Vapor Domes   Note: This subunit is covered by the reading assigned beneath subunit 2.2 (North Carolina State University: Professor Boles’ Lecture Notes on Thermodynamics: “Chapter 2: Properties of Pure Substances”).  Study the vapor domes sketeched on pages 7–11.  Find out what is the critical temperature for water.

2.3 Liquids and Vapors   - Reading: North Carolina State University: Professor Boles’ Lecture Notes on Thermodynamics: “Chapter 2: Properties of Pure Substances” Link: North Carolina State University: Professor Boles’ Lecture Notes on Thermodynamics: “Chapter 2: Properties of Pure Substances” (PDF)

Instructions: Please click on “Study Guide for Chapter 2.”  Please read pages 2–8 to pages 2–33.  In this reading, you will learn about the relationships governing the properties of pure substances (e.g. water).  You will also learn how to use the liquid-vapor tables to calculate properties of a pure substance as functions of pressure, temperature, and specific volume.  Note that this reading will cover the material you need to know for subunits 2.3.1–2.3.3.

• Reading: Dr. Israel Urieli’s Lecture Notes on Engineering Thermodynamics – A Graphical Approach: “Chapter 2: Pure Substances” Link: Dr. Israel Urieli’s Lecture Notes on Engineering Thermodynamics – A Graphical Approach: “Chapter 2: Pure Substances” (PDF)

Instructions: Please click on the link to Chapter 2a:Phase Change, Property Tables, and Diagrams” and read the entire document.  What is a critical point?  What are the most common methods to show properties of pure substances?

Terms of Use: The linked material above has been reposted by the kind permission of Israel Urieli, and can be viewed in its original form here.  Please note that this material is under copyright and cannot be reproduced in any capacity without explicit permission from the copyright holder.

• Web Media: National Institute of Standards and Technology (NIST): NIST Chemistry Webbook’s “Themophysical Properties of Fluid Systems” Link: National Institute of Standards and Technology (NIST): NIST Chemistry Webbook’s “Themophysical Properties of Fluid Systems” (HTML)

Instructions: Use the website to look up properties for water and other fluids.  Follow the instructions on the website to generate saturation properties for water.

2.3.1 Saturation and Quality   Note: This subunit is covered by the reading assigned beneath subunit 2.3 (North Carolina State University: Professor Boles’ Lecture Notes on Thermodynamics: “Chapter 2: Properties of Pure Substances”).  Focus on pages 15-17.  What is quality of steam?  How does the quality of a vapor-water mixture change as we increase its pressure?  What is a saturated state?  What are saturation temperature and saturation pressure?

2.3.2 Using the Liquid-Vapor Tables   Note: This subunit is covered by the reading assigned beneath subunit 2.3 (North Carolina State University: Professor Boles’ Lecture Notes on Thermodynamics: “Chapter 2: Properties of Pure Substances”).  Study the saturated water tables on pages 12-14 carefully.  What is the internal energy of saturated liquid water at 0.1 MPa?

2.3.3 Compressed Liquids and Superheated Steam   Note: This subunit is covered by the reading assigned beneath subunit 2.3 (North Carolina State University: Professor Boles’ Lecture Notes on Thermodynamics: “Chapter 2: Properties of Pure Substances”).  Study the saturated water tables on pages 12-14 carefully.  Review tables A-6 and A-7 carefully.

• Web Media: YouTube: EdwardsVacuum’s “Water Phase Change – Water to ice” Link: YouTube: EdwardsVacuum’s “Water Phase Change – Water to ice” (YouTube)

Instructions: Watch the video (1.42 min); can you explain how water changes to ice when pressure is reduced?

2.4 Equation of state   - Reading: North Carolina State University: Professor Boles’ Lecture Notes on Thermodynamics: “Chapter 2: Properties of Pure Substances” Link: North Carolina State University: Professor Boles’ Lecture Notes on Thermodynamics: “Chapter 2: Properties of Pure Substances” (PDF)

• Reading: University of Notre Dame: Professor J. M. Powers’ Lecture Notes on Thermodynamics: “Chapter 3: Properties of Pure Substances” Link: University of Notre Dame: Professor J. M. Powers’ Lecture Notes on Thermodynamics: “Chapter 1: Introduction to Thermodynamics” (PDF)

Instructions: Please browse through section 3.4.  The reading will provide you with some historical background on the equations of states for ideal gases and gas mixtures.  Pay attention to Figures 3.13 and 3.14.

2.5 Gases   2.5.1 Ideal Gas Law   - Reading: North Carolina State University: Professor Boles’ Lecture Notes on Thermodynamics: “Chapter 2: Properties of Pure Substances” Link: North Carolina State University: Professor Boles’ Lecture Notes on Thermodynamics: “Chapter 2: Properties of Pure Substances” (PDF)

Instructions: Please click on “Study Guide for Chapter 2.”  Please read pages 2–38 to pages 2–45.  This reading introduces the compressibility factors, which are used to measure how an actual gas deviates from ideal gas law.  Can you provide some examples of non-ideal gas law?

• Lecture: Ideal Gas Law The Saylor Foundation does not yet have materials for this portion of the course. If you are interested in contributing your content to fill this gap or aware of a resource that could be used here, please submit it here.

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2.5.2 Compressibility Factors   - Reading: North Carolina State University: Professor Boles’ Lecture Notes on Thermodynamics: “Chapter 2: Properties of Pure Substances” Link: North Carolina State University: Professor Boles’ Lecture Notes on Thermodynamics: “Chapter 2: Properties of Pure Substances” (PDF)

Instructions: Please click on “Study Guide for Chapter 2.”  Please read pages 2–38 to pages 2–45.  This reading introduces the compressibility factors, which are used to measure how an actual gas deviates from ideal gas law.

• Reading: University of Notre Dame: Professor J. M. Powers’ Lecture Notes on Thermodynamics: “Chapter 3: Properties of Pure Substances” Link: University of Notre Dame: Professor J. M. Powers’ Lecture Notes on Thermodynamics: “Chapter 1: Introduction to Thermodynamics” (PDF)

Instructions: Please read pages 57-59.  Calculate the critical volume, temperature and pressure for a van der Waals gas.  Get familiar with the Redlich-Kwong equation of state, which is widely used for engineering calculation.  Pay attention to Figure 3.20.  Make sure that you are able to define and calculate compressibility factor and reduced properties.  Use the compressibility factor to explain why all gases approach ideal gas at low pressure.