ENTHALPY and the Properties of Water

ΔH = ΔG + TΔS

The above "Gibbs-Helmholz Equation" is one of the fundamental equations of the field of THERMODYNAMICS. Now that is a word that prompts mental blocks in most of us! So, unless you are a little kid, you had better click that link to find out why little kids understand it and you don't.

Because you now understand all about activation energy and free energy (delta G), you are ready to delve into the understanding of two of the several other types of energy in the universe: entropy (delta S) and enthalpy (delta H). Right off you will notice that the above equation says that H includes both G and S, so maybe H shouldn't be called a discrete form of energy at all as it is sort of a summation of two energies. Yes, of course, you don't really understand anything written here so far because it is given in the abstract. Let's look at a couple of examples. And remember that since thermodynamics applies to EVERYTHING in the universe, the following are true examples of real cases, and not make-believe metaphors. These examples are as real as the syphon and the roller coaster in the thermodynamics link, above.

Examples Relating Enthalpy and Free Energy

Suppose you had two toy boxes. In one you placed tennis balls that contain disks of steel, and in the other box you have placed the same number of tennis balls also with similarly sized steel disks. The only difference is that the second box contains tennis balls with disks that are strongly magnetized.

First imagine that you dump the boxes out. Where do the balls from the first box go? All over the place! Where do the balls from the second box go? Well, a few separate from the others and bounce around, but most stay clinging to each other in pairs, triplets, or even more.

You then get all the balls back in their boxes and dump the boxes from one floor up. Again those from the first box go all over the place as single, separated balls. But many of those in the second box still cling to each other - fewer than before. Afterall you have added a little energy to balls as they all fell together and then hit the pavement.

In order to add more energy, you climb higher and higher, making repeated drops. Finally, you reach a level that when the magnetized balls impact the pavement they have so much energy in them that the overcome all the magnetic force and bounce off a singles and nothing more - no doublets or triplets.

What this tells you is that you could easily "evaporate" the non-magnetic balls, but you had to add a great deal more energy to "evaporate" the magnetic balls.

Let's start over and put the balls in two special tumble dryers, which can be varied in their rotational speed. We start at a slow speed, occasionally taking a "stop-action" photograph of the contents of each dryer. Right from the start we see in the photo of dryer #1 that all the balls are separated into singles, but in dryer #2 there a clumps of balls banging around together. As we turn up the speed, the clumps in the second dryer get smaller and smaller, until we finally reach a very hectic speed and all the balls are separated.

I should be obvious that the aggitation imparted by the dryers is like the effect of temperature on molecules. The higher the temperature, the more aggitated the molecules are.

FINALLY we are ready to ask some questions. 1. What is the average molecular weight of the balls in the first dryer? (Answer: 1 tennis ball weight) 2. What is the average molecular weight of the balls in the second dryer? (Answer: it all depends on the speed (temperature), as the higher the speed, the average size of the clumps gets smaller.)

STILL HAVE MORE TO WRITE.

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