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Ideal gas
Blue molecules
Yellow molecules
Pressure / bar (average over 10 seconds):

Partial pressure

This simulation has two different types of gas molecules, blue and yellow. The molecules start moving in random directions, and they collide the walls of the container elastically so that the total kinetic energy of the system remains constant.

Learning outcomes

  • Understand the meaning of partial pressure.
  • Appreciate some of the differences between ideal and non-ideal gases.

Instructions

The 400 molecules (200 of each colour) will start moving as soon as the page loads.

When the simulation starts, the gas is simulated as an ideal gas and so the molecules will not interact with each other. If you untick the 'Ideal gas' control the molecules will collide with each other elastically.

You can remove the blue and / or yellow molecules by unticking the appropriate controls towards the bottom of the page.

The pressure of the gas is shown under the simulation. This is calculated from the momentum change when the molecules collide with the walls of the container and is averaged over ten seconds. Because of the averaging, the pressure reading may take a few seconds to settle when the simulation starts or after settings are changed.

Try changing the controls and watch the effect on the number of collisions.

The molecules may occasionally stick together when 'Ideal gas' is turned off, but they should break apart again.

Questions

  1. When the system is simulated as an ideal gas, what is the effect on the pressure of removing half of the molecules?
  2. How does allowing the molecules to collide with each other effect the effective volume?
  3. What is the partial pressure of the yellow and blue molecules when the system is simulated as an ideal gas?
  4. What happens to the pressure when the molecules are allowed to collide with each other?
  5. When the system is simulated as an non-ideal gas, what is the effect on the pressure of removing half of the molecules?
  6. What is the partial pressure of the yellow and blue molecules when molecular collisions are allowed? (You will need to do some further reading on partial pressures to answer this)
  7. In addition to allowing collisions between the gas molecules, what other effect (not simulated here) is included in the Van der Waals model of a gas? (This is not part of the Thermodynamics 1 course)