Lab Exercise 11 - Simulation
Behavior of Gases: Finding the Molar Mass of a Fictitious
Gas Using Temperature and Average Velocity
• Determine the molar mass of a fictitious gas in a simulation
• Learn the relationship between temperature and kinetic energy
The molecules of matter at ordinary temperatures can be considered to be in ceaseless,
random motion at high speeds. The average translational kinetic energy for these molecules
can be deduced from the Boltzmann distribution. Knowing the velocity and the temperature of
these molecules at different temperatures will allow us to calculate a value for the Molar Mass.
The Boltzmann distribution of energies can be broken down to relate average velocities to
temperature using the following relation:
kT = mv2
k = 1.38 x 10-23 J/K
T in Kelvin
m of a single particle in kg
v in m/s
We can eliminate the 1/2 factor by multiplying both sides by 2 giving us:
y = mx + b
You can see how this equation can be viewed and plotted as a linear relationship with v2 as the
x-axis and 3kT as the y-axis.
A. Go to the University of Colorado website for science simulations: phet.colorado.edu.
1. Click on the “Play with Simulation” button.
2. Click on “Chemistry”
3. Find the lab the says “Gas Properties” and click on it.
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4. You can either use the simulation online or download it as a .jar (Java archive) file. If you
click to play and you get a blank screen, you will need to download it.
5. Open the .jar file and run it. If you need to install Java on your computer you can do so
here https://java.com/en/download/manual.jsp. You may need to restart your computer
after installing. You may also get a message about the developer and it won’t open. If
this happens, just hold down Control and click to open the file, then open it.
B. SETTING UP THE EXPERIMENT
1. Click on “Volume” as your Constant Parameter.
2. Click on “Measurement Tools”, then select “Species Information”
3. Click on “Advanced Options” and deselect “Molecules Collide”
4. Record your data from the experiment in the table below for Temperature, Pressure, and