SimuLab 8: Avogadro's Principle

                        


Your objective is to:


Recognize the role of the number of moles (here the number of particles) in the determination of the internal pressure of a gas.


You will be able to:

State the relationship between the number of particles and the volume they occupy if pressure and temperature remain constant.


Calculate the volume when temperature and pressure remain constant.


State Avogadro's hypothesis.


Contrast number density to mass density.


Predict what happens to each parameter if the number of particles is doubled.


    1. Open SMDPlayer, select IntroAvogadro'sLaw from the Ideal Gas folder. PRESS Play. Read all the captions and follow the instructions. Go to File - Quit

      Movie gives a preliminary understanding of Avogadro's Principle from a microscopic point of view.



    2. Open SMD, select Avogadro40 in the IdealGas folder. In order to better visualize the particles, you can select Edit : Background White. To speed up the simulation, change the Iterations Between Displays to 1000. Select Show Averages.

    In this experiment you are visualizing 40 particles (displayed as a B particle type), each of which has a mass of 1.0 unit.


    3. Press Start. Observe the Pressure versus Time graph for approximately 40 time units as shown in figure 2.5. Press Pause.

    The gas is approaching equilibrium. The pressure fluctuates around an average value.

figures2/pic5c.png

Figure 2.5: Screenshot of Avogadro's SimuLab.


    4. Record the temperature T, pressure P, volume V, number of type B particles N, and the B particle mass m.

    You are collecting data for future analysis and recording it in the first row of the data table.


    5. Open Avogadro200 by selecting File - Open Preset Experiment.

    In this experiment you are visualizing 200 particles of mass 1.0. Note that the piston is now above the screen and you can not see it.


    6. Repeat Steps 3 and 4.

    You are collecting data for future analysis and recording it in the second row of the data table.

                        


Q2.45: Are there any changes in parameters other than the number of particles? If so, what are they?


                        


Q2.46: What is the relationship between the number of particles and the volume they occupy if pressure and temperature remain the same?


                        


Q2.47: What do you predict the volume to be if you have 100 particles, each with a mass of 1.0?



    7. Open Avogadro100 by selecting File - Open Preset Experiment.

    This simulation contains 100 particles of mass 1.0.


    8. Repeat Steps 3 and 4.

    You are collecting data for future analysis and recording it in the third row of the data table.

                        


Q2.48: Speculate: What do you think will happen if we increase the mass of the particles? Why? To test your speculation, move onto the next steps.



    9. Select File - Reset Experiment. Set B particle mass to m=10.

    Now this simulation contains 100 particles of mass 10.0.


    10. Repeat Steps 2 and 3.

    You are collecting data for future analysis and recording it in the fourth row of the data table.

                        


Q2.49: What happened to the parameters of temperature, pressure, and volume when you changed the mass of the particle?


                        


Q2.50: In our simulations, density'' always refers to number density  N/V. The density which you are probably most familiar with is mass density  M/V= mN/V; where M is mass, V is volume, m is mass of a single particle and N is the number of particles.


What happens to the number density when the B particle is set to a mass of m=10 in Step 7?



                        


Q2.51: What happens to the mass density when the B particle is set to mass m=10? Contrast this to the Number Density above and explain.


                        


Q2.52: What do you predict the volume would be for 175 particles of Mass=5?


                        


Q2.53: Consider two 1-liter balloons at room temperature. One balloon is filled with one mole of He gas and the other with one mole of Ne gas. How do their pressures, mass densities, and number densities compare?