Thermodynamic Equilibrium

Worksheet for this lab

Experimental Apparatus/Procedure:

• The temperature of each chamber is directly controlled by its associated thermometer. Simply click on the thermometer and move it up or down to control temperature. As the particles start to mix the thermometers will change and the readout numbers in the respective chambers will change. Note in particular the green readout which shows the number of particles in a given chamber at any given time.

• We start with only two chambers so select 2 Chambers (the default is 4 so you need to change this). Click start to get the particles moving.

• To mix the gases click on the red vertical door one time - it dissapear and allow particle exchange/mixing. Note that the total energy in the chamber is essential the number of particles times their temperature or Thermal Energy = nT

• Reset when done with one the experimental parts click the green door to seal the chambers.

• Very important note: This simulation behaves statistically (like the real world) and will produce only statistical equilbrium and not exact equilbrium. The difference between the two is small

Part I

1. For the initial conditions shown above, predict the final equilibrium temperature when the chambers are mixed.?
2. How long does it take for the temperature to equilibrate (defined as when the simulation stops)?
3. Now hit reset (twice) and stop the simulation at t = 15 seconds. Which chamber contains more particles and why is this the case at this time?
4. Again hit reset and change the temperature in chamber 1 to 100 degrees and change the temperature in chamber 2 to 200 degrees. Predict if will take a longer or shorter time to equilibrate. Explain why the equilbrium timescale is now different than in the previous case.

Part 2

Now we have 4 chambers with particles but note that there are twice as many particles in Chamber 2 as the other chambers.

1. Start mixing all 4 chambers. You should find an equilibrium temperature of 240K (approximately (also note the time at which equilbrium is achieved). Demonstrate that this is the expected equilbrium temperature.
2. Now hit reset (twice) and change the temperature in chambers 3 and 4 to 100 each and change the temperature in chamber 2 to 500. What is your predicted equilibrium temperature?
3. Predict if equilibrium will occur faster or shorter than in the previous case and again give an explanation of why the timescale changed.




Part 3

Observe this system carefully

1. Hit start. Before mixing chambers 1, 3 and 4 (do not open any of the doors to chamber 2 in this part) predict the equilibrium temperature and compare that to the actual one achieved after you open the dorres between chmabes 1 and 3 and 3 and 4.

2. Explain why the equilbrium timescale is longer in this case than in the other cases.
3. Explain why even after equilibrium has occured, there are relatively few particles in chamber 1.

4. now hit reset (twice) - Time to play Maxwell's demon: a) do not hit start yet; b) open up all the particle doors including the ones to chamber 2 (which has not particles in it). The goal of Maxell's demon game is to try to evacuate one of the chambers and seal it with zero particles in it. You can change the speed of the particles in any chamber simply by changing the temperature of the thermometer and open and close any doors arbitrarily. c) now hit start and after 10 seconds have elapsed try to produce a chamber with zero particles in it. Explain why its difficult to win Maxwell's demon game