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Entropy and the direction of change
Entropy A measure of the number of ways in which particles can be
Gas molecules move in a straight line until it collides with another gas molecule or the wall
of the container, when it then changes direction.
This shows a container with particles of petrol vapour in the left side of the container only.
When we remove the partition, we see that the particles start to move forward at random.
It is pure chance which container they end up in after a period of time.
There are 5 molecules altogether each with 2 places to be, so the total number of ways the
molecules could arrange themselves once the partition is removed is 2x2x2x2x2=32
The molecules diffuse because there are more ways of being spread out than ways of being
all in one place.
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Liquids mix because there are more ways of them being mixed than unmixed.
Some liquids don't mix due to bonds that are stronger between the molecules of one liquid
than the bonds between the molecules of the other liquid.
General rule of mixing: substances always tend to mix unless there is something stopping
them such as strong attractive forces holding one set of molecules together so they cannot
easily break away from each other and mix.…read more