UTF-8Boyle's Law Here is an Example for the Chem 352 Final Exam: It is about the behavior of Non-ideal (real) gases. The answers to the questions are in red.
Save this final as "Last_Name_Final_Exam." Save the simulation in the ORIGINAL state, with instructions on how to run it (what variables to change) and a description of the observed results, how you interpret them, and the conclusions you draw from the results to answer the original question.
The first part of the assignment is to choose a question to investigate that meets two criteria:
1. It is interesting and addresses an issue you want to learn more about by conducting a computer experiment.
2. It is specific enough to be doable -- to be able to construct a set of simple simulations in which you can investigate
the effects of specific variables one at a time (for example, mass, intermolecular forces, size of particles, temperature etc.).
The following questions are to guide you -- answer all the ones that are relevant to what you are doing and refer to previous answers if you already covered that issue in a previous question.
Your Name:{352 Class }
1. State the Question you are investigating:
{ How does the volume of the molecules affect the volume a real gas occupies? In other words, it we keep everything else constant (Temperature, Number of particles, mass of particles, external pressure, intermolecular forces) and only change the volume of the individual molecules, what affect will that have on the total volume occupied by the gas?
}
2. Explain why this quesion is interesting:
{ Most REAL gases behave non-ideally in some range of pressure or temperature and we need to understand how they behave. Ideal gases are assumed to have NO intermolecular interactiosn and to have essentially zero molecular volume. Clearly this is not realistic, especially when the pressure is high or the temperature is low.
}
3. Explain why this quesion is specific enough to be testable with simulation so as to give a definite answer.
{ We are only going to change one variable -- the volume of the molecules and this is something we can do with the tools we have in Molecular Workbench.
}
4. Describe your reasoning in building the simulation the way you did, the testing you did, and changes you
had to make to make it work.
{ We will build two simulations and run them side-by-side. They will be identical in all variables except the one we are
testing -- the size of the molecules. The volume of each gas can change because we will have a piston with a constant external force resting on each gas that can move up and down. After equilibration, the internal pressure will equal the external pressure in each case and since the external pressure is the same for each simulation, the internal pressure (= pressure of each gas) will be the same when equilibrium is reached. We want to keep the temperature fixed so will use a heat bath.
}
5. What variables will stay fixed for the experiment and how did you choose the values for those variables?
{See above for variables we need to control. We chose enough molecules so the volume does not fluctuate too much but not so many molecules that there is too much crowding. We chose a high enough temperature so the that the molecules have enough Kinetic Energy that we don't get bored waiting for them to move, but not so much that the pressure builds up to much. We chose the external pressure so the volume at equilibration is some where in the middle of the simulation box.
}
6. What variable will you change to answer the question? Over what range of values will you test the effect of the variable?
{We will change the volume of the molecules. For one simulation we will make the volume quite small and for the other considerably larger. We will make sure not to introduce inter-molecular attractions when we change the size.
}
7. What variables will you monitor or measure? How will you output or measure them? Examples of variables we
have output include the volume, the temperature (or average KE), the total energy, the potential energy, the arrangements of
particles, etc.
{We will monitor the height of the piston in each simulation and this will indicate the volume. The higher the piston the greater the volume.
}
8. Usually you need to equilibrate your simulation before running to measure results. Will you equilibrate your simulation with the heat bath on (Isothermally) or without the heat bath -- i.e. Adiabatically? Explain.
{We will equilibrate isothermally -- i.e. with the heat bath ON to keep the temperature fixed. The pressure will equilibrates during the running of the simulation. When the volume stops changing, the internal pressure will equal the external pressure and the simulation will have reached equilibrium.
}
9. When you actually run the simulation -- will you do it with the heat bath on or off? Explain.
{
See answer to 8.
}
10. Provide directions for someone else to run your simulations to reproduce the experiments you got, and describe the results you obtained:
{
Start each simulation and run each until the volume in each simulation stops changing except for small fluctuations. Then compare the volumes to see if they are equal or one is greater.
}
11. State the answer to your question and intepret the results in terms of relevant fundamental concepts (for example, Conservation of momentum, conservation of energy, conservation of charge, Coulomb's Law, Entropy, etc.). Any surprises?
{The simulation shows that the volume of the molecules affects the volume occupied by a gas. Gases with larger molecular volumes will occupy larger total volumes. This is taken into account in the Van der Waals equation and other equations developed for real gases.
}
Build simulations Here:
14true1414141414141414true14true1414true14true14true255 0 014true255 0 014true14255 0 014255 0 014true255 0 014true14255 0 014255 0 014true255 0 014true14255 0 014255 0 014255 0 014true14true14true14255 0 014255 0 014255 0 014255 0 014255 0 014255 0 014true255 0 014true14255 0 014255 0 014255 0 014255 0 014255 0 014255 0 014true255 0 014true14255 0 014255 0 014true14true14true14true14255 0 014255 0 014255 0 014true14255 0 014255 0 014255 0 014true255 0 014true14255 0 014255 0 014255 0 014true14true14255 0 014255 0 014255 0 014true14true14255 0 014255 0 014true14true1414org.concord.mw2d.activity.AtomContainerFinal_Exam_Example$0.mmlorg.concord.mw2d.activity.AtomContainerFinal_Exam_Example$1.mml1414141414