Everyday entropy: coal anyone?

20120425kesselwand
Coal burner

If entropy is confusing for you, it’s because you think you understand energy when you don’t.  Energy isn’t a thing that you get from coal and distribute through an electricity grid.  That is like “energetics” or the “caloric” theory of energy that existed before modern thermodynamics.  The energy in the coal doesn’t go anywhere.  When the coal burns, the entropy of the system increases.  That increase is translated into temperature in the boiler, which is translated into space in the steam, which is translated into pressure in the pressure vessel, which is translated into force in the turbine, which is translated into force in the drive shaft, which is translated into charge in the dynamo, which is shared with the circuits in your toaster, which is translated back into temperature in the element, which is shared with your bread, which leaves you with toast.  All of the energy in the coal is fully accounted for in the byproducts at the power plant.  If you do the stoichiometry, you’ll see that it didn’t go anywhere.  There was, however, a very clever set of contraptions that established a relationship between your toast and the burning coal, so that you got to share in a bit of the increase in entropy.  It’s much easier to think of this in terms of energy as sort of an abstract force that can be sent from here to there in different forms, but that convenience means that we are left with this confusing concept of entropy for all of the physical relationships that make the energy happen but don’t fit our conception of what energy is.

Industrial chemical production follows the same pattern, where entropy increases spectacularly at the production site so that highly reactive chemicals with phenomenal potential energy can create sudden and violent reactions somewhere far from the site of the increased entropy.  It looks like magic:  Dry ice, polyester yarn, bleach, cement.

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