Entropy and disorder
Entropy can be interpreted statistically as a measure of disorder. The higher entropy, the higher disorder. The examples given in the main article are now reviewed in the light of disorder. What does it mean if one says disorder becomes larger when a body is heated?
Heating and cooling
In the first problem a body was heated and another one is cooled. It was stated that entropy increases on heating. Does disorder increase, too?
Yes, it does. Remember what you know about how heat is stored in a piece of matter. It is stored as the random motion of particles. The hotter a body, the more its atoms and molecules jiggle around. It is not difficult to identify disorder by faster jiggling motion.
Mixing
Problem 3 (mixing of gases) and problem 6 (mixing of liquids) are similar as viewed from statistic interpretation of entropy. Mixing is the tipical example for disorder. A comment is hardly needed. Just imagine, say, all your floppy disks mixed at random! Wouldn't you call that disorder?
Evaporation
Problems 4 and 5 showed that entropy is larger for gaseous phases than for condensed (liquid, solid). From the statistical point of view this is similar to mixing. It is like having ones floppy disks within a disk box or scattered all over the place.
Solid and liquid
Solids have lesser entropy than liquids (problems 7 and 8). Statistically, in solids the atoms or molecules are in their fixed places, whereas in liquids and even more in gases you never know exactly where to find them. The fixed sequence of atoms in solids reflects a higher ordered state.
Definition and interpretation
Again, it has to be emphasized, that interpretation and definition have to be carefully distinguished. Thermodynamic quantities are not defined statistically. For ordinary matter, this is not that important. Often, it is even easier to think of entropy as of "a measure for disorder". But we never know when we stumble over a case where the interpretation is not valid anymore. No problem, if it does not give you any result, for then at least you realize that it is not valid. But frequently, you get wrong results without being aware of it, and then you are not very well off. So stick to the proper definition.
Last update Okt. 28, 1997 gVa