UTF-8Boyle's Law Here is an Example for the Chem 352 Final Exam: 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 gas occupies. In other words, it we keep everything else constant (Temperature, Number of particles, mass or particles, external pressure) and only change the Volume of the individual molecules, will that change affect the volume occupied by the gas.
}
2. Explain why this quesion is interesting:
{ Most REAL gases behave non-idally in some range of pressure or temperature and we need to understand how they work.
}
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.
}
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 can change because we will have a piston with a constant external
force applied to it. 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. We will
use a heat bath so we keep the temperature fixed.
}
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
that there is too much crowding. We chose a high temperature to have enough so 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 high.
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 volume of molecules.
}
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 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. It equilibrates during the running. When the volume stops changing, we 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 volume in each simulations stops changing except for small fluctuations. Then compare the volumes.
}
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 volumes.
}
Build simulations Here:
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