Gas

General info

  • to adjust image size / rotate image, use mouse wheel / hold right button on mouse
  • to run simulation, select: “start” button

1. visualize frequency of gas molecule collision as a function of volume

Based on: stockroom -> elements -> noble gas [alternative: tutorials -> #35 mean free path; part B]

  • Properties -> thermodynamics -> volume
  • Models -> collisions -> molecule to molecule
  • use mouse to select a gas molecule, then: Models -> trails
  • run simulation
  • observe frequency of collisions –> usually, there’s no collision among gas molecules = usually, there’s no interaction among gas molecules; they simple collide into system’s walls, which could be described by physics concept – conservation of momentum
  • increase volume ~ 100 times, then observe frequency of collisions . . . decrease the length of the mean free path

2. visualize relative speed as a function of molar mass & temperature

Based on: tutorial -> gas -> # 33 describing mixture … [file = mass_temperature]

  • Properties -> speed, molecule - 3 times; select each molecule
  • Properties -> molecule -> molar mass => to confirm identity: H2 vs. N2
  • Properties -> thermodynamics -> temperature
  • run simulation
  • examine (i.e. visual & numerical values) relative speed
  • vary temperature; examine relative speed among molecules & same molecule @ different temperature

3. relate speed / KE versus atomic mass

Based on: Molecular Stockroom -> Elements -> Noble gas

  • Plots -> XY Plots -> __; -> Next -> Scatter Plot -> Finish
  • x-axis = atomic mass; y-axis = average speed
  • Properties -> Dynamics -> speed
  • Properties -> Energy -> KE
  • Properties -> thermodynamics -> temperature
  • run simulation
  • on graph, “select atom” -> select atom in simulation -> run -> select red dot; note temperature & KE; repeat for all gases
  • note: as increase atomic mass, temperature & KE is relatively stable, while speed decreases. Collect data: atomic mass versus velocity
  • consistent with equations (qualitative & quantitative):

rearranging preceding equation:

4. relate temperature to speed / KE histogram

Based on: Molecular Stockroom -> Elements -> Noble gas

  • Plots -> speed distribution; adjust (use pencil icon) Vmax = 5000 m/s with 4 tickmarks
  • Plots -> trans. KE distribution; adjust (use pencil icon) KE max = 50 kJ/mol with 4 tickmarks
  • Properties -> Dynamics -> speed
  • Properties -> Thermodynamics -> temperature
  • Properties -> Energy -> KE
  • adjust windows: reduce radio button region by expand animation region; adjust graph region accordingly to see both graphs
  • Run simulation
  • adjust (use pencil icon) to 300 gas molecules for all gases
  • select He; vary temperature & observe effect on histograms & values of speed & KE
  • repeat with Rn - similar behavior

5. compare diffusion versus effusion

Based on Molecular labs -> gas -> # 25 The ability of gas to mix [file = diffusion]

  • run simulation
  • run; observe gas molecule motion
  • move cursor to barrier; right-click on mouse; select: remove partition; run; stop
  • note: different rate of diffusion between gas molecules (CO vs. H2) based on relative time for H2 compared to CO to “fill” other side of container

Based on Molecular labs -> gas -> # 34 The effusion of gas mixture [file = effusion]

  • similar to preceding simulation – using right mouse button

6. illustrate nonideal gas behavior: He vs. Rn

Based on: Molecular Stockroom -> Elements -> Noble gas

  • Plots -> XY plots -> __; advanced -> allow for multiple curves; 1 curve for each sample -> OK -> next -> smooth fit -> finish
  • x-axis = pressure; y-axis = PV/nRT
  • Properties -> thermodynamics -> volume
  • Properties -> thermodynamics -> pressure
  • Properties -> other -> PV / nRT
  • run simulation; select He & Rn
  • run; select data (red button)
  • various volume (to vary pressure); run; select data (red button); repeat till get data up to ~ 50 atm
  • adjust axis scale & tick marks (pencil icon)