# Top-rated ScreenCasts

Text Section | Link to original post | Rating (out of 100) | Number of votes | Copy of rated post |
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01.2 Molecular Nature of Temperature, Pressure, and Energy | Click here. | 60 | 9 |
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 |

14.04 LLE Using Activities | Click here. | 60 | 2 |
Txy Phase Diagram Showing LLE and VLE Simultaneously (9min,uakron.edu) The binary Txy phase diagram of methanol+benzene is visualized with k) increases, the LLE boundary crashes into the VLE. It is so exciting that it makes a thermo nerd wax poetic about the "valley of Gibbs."_{ij}Comprehension Questions: 1. The LLE phase boundary moves up as the nonideality increases. Which way does the VLE contribution move? Explain how this relates to the molecules' escaping tendencies. 4. What value of kis required to make the LLE binodal barely touch the VLE at 10 bars?_{ij } |

11.02 - Calculations with Activity Coefficients | Click here. | 60 | 2 |
This example shows how to predict activity coefficients in Excel using the Margules Acid-Base (MAB) model.(8min, uakron.edu) Sometimes you just need a quick estimate of whether to suspect an azeotrope or LLE or some other anomalous behavior. If the MAB model indicates a possible problem, it's time to go to the library or the lab and validate your model with experimental data. Note: This is a companion file in a series. You may wish to choose your own order for viewing them. For example, you should implement the first three videos before implementing this one. Also, you might like to see how to quickly visualize the Txy analog of the Pxy phase diagram. If you see a phase diagram like the ones in section 11.8, you might want to learn about LLE phase diagrams. The links on the software tutorial present a summary of the techniques to be implemented throughout Unit3 in a quick access format that is more compact than what is presented elsewhere. Some students may find it helpful to refer to this compact list when they find themselves "not being able to find the forest because of all the trees." Comprehension Questions |

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

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. |

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: |

03.6 - Energy Balance for Reacting Systems | Click here. | 60 | 1 |
Heat Removal from a Chemical Reactor (uakron, 8min) determines heat removal so that a chemical reactor is isothermal following the pathway of Figure 3.5b using the pathway of Figure 2.6c if a heat of vaporization is involved. The reaction is: N2 + 3H2 = 2NH3 at 350C and 1 bar. The pathway to go from products to the reference condition is to correct for any liquid formation at the conditions of the product stream then cool/heat the products to 25C (the reference temperature), then "unreact" them back to their elements of formation. Summing up the enthalpy changes over these steps gives the overall enthalpy of the reactor outlet stream. The same procedure applied to the reactor inlet gives the overall enthalpy of reactor inlet stream. Then the heat duty of the reactor is simply the difference between the two stream enthalpies. Comprehension Questions: |

03.1 - Heat Engines and Heat Pumps: The Carnot Cycle | Click here. | 56.6667 | 6 |
Introduction to the Carnot cycle (Khan Academy, 21min). 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, η = (_{θ}T)/_{H} - T_{C}TH, where Tis the hot temperature and _{H} Tis the cold temperature. We can use this formula to quickly estimate the thermal efficiency for many processes. We will show in Chapter 5 that this formula remains the same, even when we use working fluids other than ideal gases (e.g. steam or refrigerants)._{C }Comprehension Questions: 4. What value of Twould be necessary to approach 100% efficiency, even for this idealized, maximally efficient process? What are the practical limitations on _{H} T? Explain. _{H}5. How can the formula for Carnot efficiency help us to calculate the "lost" work in the presence of a temperature gradient? |

11.06 - Redlich-Kister and the Two-parameter Margules Models | Click here. | 56.6667 | 6 |
Two-parameter Margules Equation (5:05) (msu.edu) An overview of the two parameter Margules equation and how it is fitted to a single experiment. |