Chapter 12: The Law of Increasing Disorder

(Press the TAB key to position the cursor at the beginning of the first blank and type what you believe completes the thought. Then press the TAB key for feedback and to move to the next blank. If you miss it, delete all of the word by positioning the cursor with the mouse and backspacing over all of the letters and try again. You should be able to complete this exercise without error before completing this chapter.)

The Second Law of Thermodynamics is sometimes called the Law of Increasing Disorder. The Second Law of Thermodynamics addresses (among other things) the question: Why does have a direction? An ice cube in a glass of water on the counter will melt, but it never happens that an ice cube spontaneously appears in a glass of water on the counter. Why? An "irreversible process" is one that occurs in one way but never in exactly the reverse way. The Second Law of Thermodynamics: "Changes occurring in natural systems always proceed in such a way that the amount of (order, disorder?) in the universe is unchanged or increases. If the total disorder is increased, the process is (reversible, irreversible?) ." "Entropy is the technical name for disorder and it has a mathematical definition that is not particularly useful for us here. Instead, we try to define increasing disorder by a series of example in which there is a common underlying thread: First, one may separate molecules into individual places. Separating colored sugar grains (colored with dye molecules in food coloring, some blue, some green, etc. but mixed together) into separate piles according to color is an ordering process. Mixing them all together is a disordering process. Refining ore by separating raw ore into separated molecules of, say, silver, lead, and zinc is an ordering process. Mixing them back together is a disordering process. Second, one may separate molecules into different groups characterized by different internal energies rather than by different species. Creating a piece of ice from surrounding water is an ordering process. The molecules in the piece of ice have a lower internal energy than the same kind of water molecules in the surrounding liquid water. The separation of the molecules into these two classes constitutes an ordering process. Melting the ice cube and remixing the molecules is a disordering process. Operating a refrigerator is an ordering process because the refrigerator creates a class of air molecules inside the refrigerator with a low internal energy (low temperature) that is separate and distinct from the same kind of air molecules outside the refrigerator but with higher temperature. Turning off the refrigerator and opening the door mixes the molecules and destroys the separation, i.e., it is a disordering process. Third, one may speak of forms of energy themselves as being ordered or disordered if the energy has potential to form order in the first and second senses above. Nuclear potential energy that can be released in a bomb is an ordered form of energy because the release of energy creates an extremely hot class of molecules that is separate and distinct from the molecules of lower temperature at a distance from the exploding bomb. The common thread in the examples is that the separation and mixing of molecules creates (order, disorder?) and (order, disorder?) respectively. Some forms of energy arranged from most order to least ordered are: Macroscopic and gravitational potential energy, nuclear potential energy, household energy. chemical energy, ambient temperature energy. The Second Law of Thermodynamics may be restated: "Any form of energy (on the above list) can be totally converted to any other form which has the (same, less?) or more disorder, but it (can, cannot?) be converted totally to another form in wh;ich it would have (more, less?) disorder." The Second Law of Thermodynamics does NOT prohibit the increase of order. It says that in a closed system, you may indeed create order in part of the system, but only at the expense of increasing disorder somewhere else in the system. A refrigerator (cold molecules inside, warm molecules outside) and an automobile (with macroscopic kinetic energy) both create order, but at the expense of overall increasing disorder in the universe. When left to themselves, all systems eventually change to the arrangement with maximum disorder. This state of maximum disorder is called (thermodynamic) . No further macroscopic changes occur in the system once the system reaches this state. Because the universe itself is believed to be such a closed system, it is thought to be approaching equilibrium. This equilibrium is called the "heat death" of the universe.

Click here to return to the Table of Contents