Virtual Substance

Partial Derivatives Are You Kidding Teaching Thermodynamics Using Virtual Substance... 

Inquiry-driven student learning of thermodynamics is achieved with the implementation of the Virtual Substance molecular dynamics simulation program. Problem solving and critical thinking skills are developed by students through the completion of the modules described in this chapter. In addition, Virtual Substance is shown to be exceptionally numerically accurate as a tool for doing authentic science. 

As instructors of physical chemistry, we all too often hear comments like the one in the title of this chapter. The prevailing attitude with which many students approach physical chemistry is one of fear for their academic survival. The concerns they have are not so much with the chemistry but with the math. For some students, the physical chemistry course is the first time they must authentically apply advanced mathematical concepts to solve real problems. Instructors can facilitate this transformation with exercises that demand critical thinking skills, but developing such materials requires extensive time and talent. The Virtual Substance molecular dynamics program is a powerful tool in our efforts as educators to help students successfully transition from abstract knowledge of mathematics to its application to scientific concepts. 

Virtual Substance simulations can be run using either periodic boundary conditions or fixed walls. In a fixed wall calculation, the simulation box has physical walls. The resulting system is a droplet , albeit a rectangular droplet, and as a result, the thermodynamic properties differ from those of the bulk substance. One can create a bulk substance by using periodic boundary conditions where the simulation box interacts with copies of itself repeated in three dimensions. (5) This approximates the extended nature of a bulk material, making it appear infinite, and results in better accuracy in the calculation of thermodynamic properties. 

Virtual Substance can be used as supplemental homework assignments in the physical chemistry lecture course or as laboratory modules for a physical... 

Figure I. a) Virtual Substance model building interface b) Sample generated substance.

One of the over-arching goals of physical chemistry is to explain real systems by building upon what we know about ideal systems and examining the limitations of those idealized models. The study of real gas behavior using Virtual Substance is one of the most eye-opening assignments for the students. 

In this lab, the students determine the compression factor, (9) Z = PV/nRT, for Argon using the hard sphere model, the soft sphere model, and the Lennard-Jones model and compare those results to the compression factor calculated using the van der Waals equation of state and experimental data obtained from the NIST (70) web site. Figure 3 shows representative results from these experiments. The numerical accuracy of the Virtual Substance program is reflected by the mapping of the Lennard-Jones simulation data exactly onto the NIST data as seen in Figure 3. 

Table 1. Topics that can be investigated with Virtual Substance...

It helped without my realizing it was helping. To hear the words "partial derivative" sends chills down my spine but I remember the math for Virtual Substance being easier. 

I m a big fan of figuring things out for myself. Because Virtual Substance allowed me to do my own thing I feel like I understood better what I was doing because it was me doing all the work from the beginning. 

It gave me a better understanding of what was really going on in the real experiments in lab. Virtual Substance allowed you to see inside the container, visualizing the actual gas particles. ... 

The Virtual Substance program can reinvigorate the learning of a broad set of thermodynamic topics as seen in Table 1, the list given to students for... 

CDB would like to thank the Bell Grant fund at Erskine College for summer support. The development of the Virtual Substance software program was supported in part by NSF grant CHE-0301266 awarded to JMP. We also want to thank our students for participating in this endeavor. 

Virtual Substance University of North Carolina. Also see contribution by C.D. Bruce and J.M. Papanikolas elsewhere in this book. 

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