Lab Module #7
Real Substances in the Ideal Limit
Introduction to VS
Noon, Tuesday, October 20
Submit via Blackboard
For this module, you should submit a Word doc.
No intro, no research problem,
no conclusions - just observations, comments, any necessary data tables from Excel, as
requested in the procedure.
Be sure to answer the questions contained in each section below.
To explore the molecular dynamics program, Virtual Substance; to learn how to perform
thermodynamic measurements with Virtual Substance; and to examine the physical properties
of real gases in the ideal gas limit.
Virtual Substance (VS) is a molecular dynamics program that simulates the properties of substances in the
solid, liquid, and gaseous phases. The program provides a 3-dimensional view of the simulation volume
that shows the motion of the particles during the course of the calculation.
This week’s lab is an
introduction to the workings of VS, including an investigation of the extent to which VS simulates
experimentally-observed behavior of real substances (in this case, monatomic gases).
In order to download VS to your computer, follow the directions from the VS folder in Course
Documents on Blakboard.
The program runs under Win 98/2000/XP (OpenGL required).
Atkins, Physical Chemistry
: review the gas laws, compression factor and Lennard-
section 1, 2.0, 2.1, 2.3, 3.0, 3.3 (MD)
A central goal of physical chemistry is to understand how the forces between the particles in a
substance give rise to its physical properties.
We will begin our study of substances with the
gas phase; not only have gases been extensively studied, but the vast distances between
individual particles in a gas at low pressures and large volumes simplifies the description
necessary to accurately model them.
Ideal gas behavior:
Argon, for example, in the low-density context, could be described as a
collection of "point" particles that do not interact with each other. That is, there are
intermolecular forces. This ideal gas model gives rise to the ideal gas law, which provides a
relation between the pressure (P), the volume (V), and the temperature (T):
where n is the number of moles of gas. The ideal gas model is not the only model, and as it
turns out, one could envision a variety of other ways in which to describe this simple gas.
will explore other models in a future lab.
Our goal is to have a model that extends the ideal gas law (which assumes no IM forces).