The quantum casino: simulations

# Entropy and disorder

This simulation lets you look at the outcome of a process that occurs entirely randomly. Although we can draw lessons from what happens, it makes no real attempt to model an actual chemical process. Up to 200 objects can be placed in either of two boxes as a starting position. These then move entirely at random from one box to the other. This is a little like molecules of gas in gas jars but the simulation makes no attempt to model their actual motion. You can use the two sliders to vary the total number of objects and the number in each box at the start. (As a tip, it probably makes sense to start with all the objects in one box or the other initially.) The histograms below each box show a running total of the number of objects in each box. You can step through the simulation one move at a time or let the simulation run for as long as you like – the ‘run’ option will be better once you have go the idea of what is happening.

## Conclusion

You should have found that whatever the starting position, the objects end up evenly distributed between the two boxes – this totally predictable result produced entirely at random. In fact the distribution is not entirely even, there are small statistical variations – you can see the histograms wavering slightly. But these variations become less significant as the number of objects increases. If this trend continues and we apply it to realistic numbers of molecules for an everyday amount of substance (say 1 mole; 6 x 1023 particles) then we will get an entirely predictable outcome from an entirely random process. This is an important lesson that we will be able to apply to real chemical systems later.

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