# Top-rated ScreenCasts

Text Section | Link to original post | Rating (out of 100) | Number of votes | Copy of rated post |
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04.02 The Microscopic View of Entropy | Click here. | 65 | 4 |
Principles of Probability I, General Concepts, Correlated and Conditional Events. (msu.edu, 17min) (Flash) |

04.02 The Microscopic View of Entropy | Click here. | 65 | 4 |
Principles of Probability II, Counting Events, Permutations and Combinations. This part discusses the binomial and multinomial coefficients for putting particles in boxes. The binomial and multinomial coefficient are used in section 4.2 to quantify configurational entropy. (msu.edu, 16min) (Flash) You might like to check out the sample calculations below before attempting the comprehension questions. |

01.2 Molecular Nature of Temperature, Pressure, and Energy | Click here. | 63.3333 | 12 |
Molecular Nature of Internal Energy: Configurational Energy. (uakron.edu, 19min) Making the connection between " U."
Comprehension Questions:
For 1-4, assume 100 molecules are held in a cylinder with solid walls. A piston in the cylinder can move to adjust the density. RT increase, decrease, or stay the same?5. Molecules A and B can be represented by the square-well potential. For molecule A, σ = 0.2 nm and ε = 30e-22 J. For molecule B, σ = 0.35 nm and ε = 20e-22 J. Sketch the potential models for the two molecules on the same pair of axes clearly indicating σ's and ε's of each species. Start your x-axis at zero and scale your drawing properly. Make molecule A a solid line and B a dashed line. Which molecule would you expect to have the higher boiling temperature? (Hint: check out Figure 1.2.) 6. Sketch the potential and the force between two molecules vs. dimensionless distance, r/σ, according to the Lennard-Jones potential. Considering the value of r/σ when the force is equal to zero, is it greater, equal, or less than unity? |

01.5 Real Fluids and Tabulated Properties | Click here. | 60 | 2 |
Steam Tables (LearnChemE.com) (5:59) calculate enthalpy of steam by interpolation |

03.1 - Heat Engines and Heat Pumps: The Carnot Cycle | Click here. | 60 | 2 |
Heat Engine Introduction (LearnChemE.com, 6min) introduction to Carnot heat engine and Rankine cycle. The Carnot cycle is an idealized conceptual process in the sense that it provides the maximum possible fractional conversion of heat into work (aka. thermal efficiency, Comprehension Questions: |

08.07 - Implementation of Departure Functions | Click here. | 60 | 2 |
Helmholtz Departure - PR EOS (uakron.edu, 11min) This lesson focuses first and foremost on deriving the Helmholtz departure function. It illustrates the application of integral tables from Apx. B and the importance of applying the limits of integration. It is the essential starting point for deriving properties involving entropy (S,A,G) of the PREOS, and it is a convenient starting point for deriving energetic properties (U,H). |

05.5 Liquefaction | Click here. | 60 | 2 |
Joule-Thomson Expansion (LearnChemE.com, 7min) describes the Joule-Thomson coefficient - ( Comphrehension Questions: 1. Referring to the table for R134a in Appendix E-12, compute the fraction liquid at 252K after throttling from a saturated liquid at 300K. 2. Referring to the table for R134a in Appendix E-12, compute the fraction liquid at 252K after expanding a saturated liquid at 300K through a reversible turbine. |

10.03 - Binary VLE using Raoult's Law | Click here. | 60 | 2 |
Raoult's Law (5:39) (msu.edu) |

08.08 - Reference States | Click here. | 60 | 2 |
Thermodynamic pathways of EOS's for arbitrary reference states (uakron.edu, 20min) The development of a thermodynamic pathway from an arbitrary reference state to a given state condition is independent of the thermodynamic model. It depends only on (1a) identifying the condition of the reference state (e.g. ideal gas, real vapor, or liquid) (1b) transforming from the reference state to the ideal gas, if necessary (2) transforming from the ideal gas at the condition of the reference state to the ideal gas at the given state condition (3a) identifying the condition at the given state (3b) transforming from the ideal gas at the given state to the real fluid at the given state. The methodology is illustrated for two thermodynamic models: the 16 sample calculations (8 for H and 8 for S) and comparisons between PREOS vs P. You might like to refer back to Sections 2.10 and 3.6 to review the ^{sat}/H^{vap}Pmodel and the elemental reference state. Push pause before each sample calculation and check whether you can predict the next answer.^{sat}/H^{vap }Comprehension Questions: 1. Compute "H" by hand for propane at 80C and 3 MPa relative to a reference at 230K and 1bar, assuming 2. Compute "S" by hand for propane at 80C and 3 MPa relative to a reference at 230K and 1bar, assuming Cp = 8.85 and the PR EOS. You may use PREOS.xlsx to compute S-Sig, but you must show your hand calculations for each step (1a-3b). Compare your answer to the result tabulated in PREOS.xlsx.^{ig}/R 3. Compute "H" by hand for propane at 80C and 3 MPa relative to a reference at 230K and 1bar, assuming Cp = 8.85 and the ^{ig}/R Pmodel. Show your hand calculations for each step (1a-3b). Compare your answer to the result tabulated in PREOS.xlsx.^{sat}/H^{vap }4. Compute "S" by hand for propane at 80C and 3 MPa relative to a reference at 230K and 1bar, assuming Cp = 8.85 and the ^{ig}/R Pmodel. Show your hand calculations for each step (1a-3b). Compare your answer to the result tabulated in PREOS.xlsx.^{sat}/H^{vap } |

09.10 - Saturation Conditions from an Equation of State | Click here. | 60 | 2 |
Solving for the saturation pressure using PREOS.xls simply involves setting the temperature and guessing pressure until the fugacities in vapor and liquid are equal. (5min, learncheme.com) It is not shown, but it would also be easy to set the pressure and guess temperature until the fugacities were equal in order to solve for saturation temperature. One added suggestion would be to type in the shortcut vapor pressure (SCVP) equation to give an initial estimate of the pressure. Rearranging the SCVP can also give an initial guess for Tsat when given P. This presentation illustrates a Comprehension Questions: 1. Estimate the vapor pressure (MPa) of n-pentane at 450K according to the PREOS. Compare your result to the value from Eq. 2.47 (SCVP) and to the Antoine equation using the coefficients given in Appendix E. What do you think explains the observations that you make? |