Q: You're whipsawing me. A while back you said the second law was the mother of all Murphy's Laws. Now you show me that the second law is a good buddy because we can use it for energy to do what we want. That's double-talk isn't it? What's the story?
A: Come off it. You're not naive. Life is full of stuff that can be either good or bad. But get ready for a shock now: [Remember what I said about the words "second law" -- that they are often code words for what the second law describes, i.e. that energy spreads out, if it can, from being localized or concentrated to becoming dispersed.]
The second law is the Greatest Good and the Biggest Bad to us.
The GOOD: Because of the second law about the direction of energy flow, life is possible.
- We can take in concentrated energy in the form of oxygen plus food and use some of that energy unconsciously to synthesize "uphill" complex biochemicals and to run our bodies, consciously for mental and physical labor, excreting diffused energy as body heat and less concentrated energy substances.
- We can use concentrated energy fuels (e.g., gasoline/coal, plus oxygen) to gather all kinds of materials from all parts of the world and, regardless of how much energy it takes, arrange them in ways that please us. Similarly, we can effect millions of non-spontaneous reactions -- getting pure metals from ores, synthesizing curative drugs from simple compounds, altering DNA:
- We can make machines that make other machines, machines that mow lawns, move mountains, and go to the moon. We can make the most complex and intricate and beautiful objects imaginable to help or delight or entertain us.
The BAD: Because of the second law -- the direction of energy flow -- life is always threatened.
- Every organic chemical of the 30,000 or more different kinds in our bodies that are synthesized by nonspontaneous reactions within us is metastable. All are only kept from instant oxidation in air by activation energies. (The loss or even the radical decrease of just a few essential chemicals could mean death for us.)
- Living creatures are essentially energy processing systems that cannot function unless a multitude of "molecular machines", biochemical cycles, operate synchronically in using energy to oppose second law predictions. All of the thousands of biochemical systems that run our bodies are maintained and regulated by feedback subsystems, many composed of complex substances.
Most of the compounds in the feedback systems are also synthesized internally by thermodynamically nonspontaneous reactions, effected by utilizing energy ultimately transferred from the metabolism (slow oxidation) of food.
When these feedback subsystems fail -- due to inadequate energy inflow,
malfunction from critical errors in synthesis, the presence of toxins or
competing agents such as bacteria or viruses -- dysfunction, illness, or death results: energy can no longer be processed to carry out the many reactions we need for life that are contrary to the direction predicted by the second law.
How's that for starters? You can't get any better for good -- that living is possible due to the second law. And you can't get much worse for bad -- that death is always possible too, due to the second law.
Q: But what happened to Murphy's Law? That isn't about death, just about less bad things that hit us.
A: You're right. Murph doesn't get that serious very often, but there are at least five thousand illnesses, diseases, "things that can go wrong" with our bodies that may not kill us. That's 5K of Murphs. These are biochemical problems that humans suffer from. But how many do most people have? Did you ever see a PDR Medical Dictionary or an AMA Home Medical Encyclopedia? They'll make you very thankful for activation energies and feedback systems that keep your bod working as well as it does (and long as it will) to counter the second law, using food and oxygen intake as your energy source.
However, let's look at the other annoyances (and disasters) that the mother of all Murphys is responsible for when things that are around us have energy concentrated inside them. That's always potential big trouble. All that has to happen, somehow, sometime, is for a little energy push -- a spark, a flame, an impact -- to get up over that activation energy hill. (Remember the energy diagram for cellulose, i.e., wood and paper? It applies to anything flammable and literally millions of other oxidation reactions, e.g., iron or any metal rusting or corroding because rusting is oxidation.)
First, problems caused by the thing or material having concentrated energy inherent in its chemicals:.
Trees catching fire a house struck by lightning
a curtain too near a candle... the forgotten cigarette left on a sofa
Mrs. O'Leary's cow kicking over a lantern in straw and burning half of Chicago
the spark from a bulldozer that started a grass fire and then a forest fire
These are all cases of exceeding an activation energy, resulting in a spontaneous reaction.
And, of course, there are many less (or equally) dramatic examples in the oxidation of metals
Rust on a tool, disfiguring or damaging it rust in a machine, hindering operation
copper oxide in an electrical socket, causing overheating and then a fire
battery cable corrosion in Chuck Yeager's X-1 that almost killed him.
Second, annoyances (or worse) due to concentrated energy in the object being present or flowing by it, but not inherent or part of its nature:
Tires that blow out hydraulic brake systems that leak suddenly under pressure
audio speakers that are fed high wattage signals 230 volts into a 115 V house circuit
winds in the air.....from gales to hurricanes, from windstorms to tornadoes.
A car going 80 around a 30 mph curve, a 747 hitting a mountain, an Indy car into the wall.
Q: Yeh. Yeh. I get the point. Or points. Know too much about car crashes. New to me, before we began to talk, was to hear that burnable stuff, like wood and paper and cloth in my room (along with the oxygen of the air) is basically a bunch of concentrated energy chemicals. But I don't have sparks or candles around to give them an activation energy kick and cause a fire. Breaking things is more of a problem to me. Is there energy locked inside a skateboard or a ski that wrecks it (and me) because it tends to diffuse or spread out?
A: Good comment and good question. It's great that you now understand
why certain things can react with oxygen and
why a spark or low flame sets off a spontaneous reaction. You also know now that all of these kinds of problems from fires to plane and car crashes to lightning to tornadoes and fires are related by the second law of thermodynamics: concentrated energy tends to spread out. (A fast moving car is a "reely reely big" bundle of concentrated kinetic energy.)
Your question about breakage is just as important because that kind of incident or accident happens to us more often than "Murphy problems" of fire that is due to energy concentrated inside the substance of the object and oxygen.
Breaking things involves concentrated energy that is initially
outside the thing that gets broken. It's the second law working in the environment of the object -- energy flowing around or through it for some reason or other and hitting it with enough energy and of the right kind to tear it apart. (Right kind? Right amount? Heat won't make a concrete bridge shatter into fragments in thirty seconds, but a strong earthquake will.) Chemists never talk about breaking things because they don't consider that to be a chemical process. The chemical nature of a ski that gets broken, for example, isn't changed. It's just two skis so far as the chemicals in it are concerned. (Try to tell that to the skier!) Technically, the chemical composition of the two pieces of ski is almost the same so chemists call a fracture a physical process.
However, in a micro sense it is a chemical process because in any break chemical bonds are ruptured all along the line of the break as well as complexly broken and reformed near that break line. It's just that the number of bonds altered is extremely small compared to all the others in the ski that are not affected and therefore a chemist would never be able to measure any composition change. Also, where and when the break will occur depends on so many factors that aren't what chemists call fundamental, such as: how the object was made, its shape, its ratio of surface area to volume, the strains and defects present in it, whether it is brittle or ductile and even the rate of application of energy to it.
But we can plot the effect of a load (mechanical force) being applied to a solid object until it breaks. (Let's choose something that is especially valuable or useful.) In the diagram at the right, the line A represents the external load on it (the "mechanical force", that is, the effect of energy striking the object); B shows the internal energy of the object; and C is a rough estimate of the "human desirability" of the object (what it is worth). All the lines (A, B, and C) are initially horizontal to indicate their respective reference states before the application of any external force or load. As the load on a particular spot on the object is steadily increased, the internal energy of the object (line B) increases regularly with the greater and greater load (line A) bearing on it. If the external load acting on the solid is increased until fracture occurs, Line B immediately falls to the starting internal energy value (except for transient heat and the quickly dispersed kinetic energy in any flying fragments).
The difference between the high point of Line B and its original (and final) energy level is labeled in the diagram above as E
ACT SOLID . This is
partly like an E
a , an energy of activation in chemistry. An E
a is the amount of energy required to start substances reacting. Then they continue to react spontaneously because of the considerably greater amount of energy evolved during the reaction. In contrast, an E
ACT SOLID is both the energy required to start a fracture and virtually the same amount of kinetic energy given out by the two separated pieces of solid.
Line C drops radically after the break, a rough indication of the far lesser value to us of the two broken pieces as compared to the original object. (Market economics, i.e., the value/price of the object before and after the break, best describes what line C represents.)
That diagram above is for a single break of a solid object. In a hurricane, wind energy is successively applied to the two fragments of the first break so that houses become scattered parts; boards often are torn into splinters. In the terrible 1995 Kobe earthquake, even concrete structures were torn apart and many portions of them reduced to rubble. At each successive step, the qualitative diagram applies -- additional load is supplied to fracture parts of the original and then those parts are again broken.
Oops. Splintered boards. Rubble. I'm afraid I have to talk about it.
Q: That's gibberish. About IT? About what?
A: About ENTROPY! Scientifically, qualitatively, entropy is simple -- entropy change is just a way of measuring exactly what we have been talking about, how much change occurs at a specific temperature when energy spreads out according to the second law.
But that word entropy has been so erroneously defined and so misused by so many people that I'm sorry that I got trapped into talking about it when were thinking about what a city looks like after a huge earthquake! That mess of broken buildings and busted bridges would be foolishly called "an example of entropy increase" by many people who aren't scientists -- and even by some chemistry teachers.
Q: What's wrong with that? My chem text says that "Entropy is disorder" and a mess is disorder, isn't it?
A: Your text may be excellent in other topics, but it's just plain dumb wrong where it says that! Entropy only involves
energy and its spreading out (and temperature), not appearance or neat patterns. Even when considering molecules precisely arranged in a crystal, any question about entropy must be like "What is the energy distribution here? How is the crystal vibrating and the molecules moving fast but almost staying in one place," not "How orderly is this pattern?" Energy, energy, energy!
Entropy is
not "disorder". No way. No how. That's an old 1890s idea that was obsolete after statistical and quantum mechanics became fully developed in chemistry. However, it hasn't yet been eliminated from a few textbooks. They may be good in other parts but they simply don't tell you the straight stuff about entropy if they use that old obsolete definition with "disorder".
Q: Hey! You can't just say a text is wrong and expect me to believe you! You'd better give me solid evidence that "entropy is not disorder" if my chem book says it is.
A: Of course. Your text is out of date because most new editions of college/university general chemistry textbooks have deleted "entropy is disorder" and adopted my approach.
Click on
entropysite.oxy.edu to ‘what’s new’ and scroll down to May 2009 to see the list of new editions that have thrown out “disorder” and now define entropy in terms of energy dispersal. (Your professor can check
http://entropysite.oxy.edu/cracked_crutch.html. This is the article that helped convince textbook authors to delete “disorder”. Also for your professor, the article at
http://entropysite.oxy.edu/entropy_is_simple/index.html describes the bases for interpreting entropy as energy dispersal and an improved approach to microstates.)
Q: OK. What IS entropy, really?
A: It's simple basically because you know about the second law -- that energy spreads out and disperses rather than staying concentrated, i.e., localized in one place. Entropy just measures what happens in that kind of process of energy dispersing. And that's why your text says that entropy is always increasing in the world -- it's because spontaneous reactions/events are what are always happening and they happen because then energy spreads out!. (Actually, we should always say "entropy
change" because we're measuring the difference in energy distribution "after" some happening versus the "before".)
More precisely: Entropy (change) in chemistry measures either by
1) how
much molecular motional energy has been spread out in a reversible process divided by the constant absolute temperature, T
S = q(rev)/T
[ q is the amount of energy (motional energy, thermal energy, "heat") that is dispersed to a system at T from the surroundings at a very very slightly higher temperature than T, or vice versa, from the system at a tiny bit higher temp than the surroundings at T. Because the temperature differences are so small, this gradual dispersal of motional energy ("heat") in either direction is essentially reversible. This is the case in phase changes, at the melting point or the boiling point. (As some more advanced texts state, when you heat a system - i.e., increasing the "how much" motional energy is in a system - by calculus you can find the
S change )];
or (2) how
spread out the original molecular motional energy (i.e. no
change in q) of a system becomes (e.g, when an ideal gas spontaneously expands into a vacuum and increases in volume or when different ideal gases or liquids mix. (No change in temperature in the processes.)
Entropy change doesn't measure "disorder"! (What are the dimensions of "disorder"? Malarkeys per minute or some such nonsense? The scientific dimensions of entropy change are joules/Kelvin.) Entropy change in chemistry measures the spreading of molecular motional ENERGY. (For more details of that kind of energy of molecules moving ["translating"] and rotating and vibrating, see
http://2ndlaw.oxy.edu/entropy.html. Your professor could check the site for instructors at
http://entropysite.oxy.edu/entropy_isnot_disorder.html)
Q: If entropy measures how much energy has been dispersed in a bunch of chemicals, and that's q, why bother with dividing by T?
A: Because you don't really have entropy (or entropy change) if you don't include that absolute temperature, T. With entropy properly defined that way you have immense power in understanding how important is any energy change to that "bunch of chemicals". Entropy change,
S, doesn't merely measure energy spreading out, it shows us exactly
how important to a system is the dispersion of a given amount of energy in that system or substance at a particular temperature.
How's this for an analogy: If a quiet library represents a low temperature system (relatively small number for T), and you yelled "HEY, YOU!" there, everybody would jump and the librarian would turn purple. However, in a football game at touchdown time (like a high temperature system, very large number for T), if you yelled "HEY, YOU!" just as loudly, nobody would notice it. The effect of the "energy spread out in your yelling" is a lot different in a library than in a stadium!
The scientific application is this: an amount of energy dispersed, say a q of 10 joules, from the surroundings (that are just infinitesimally warmer than 100 K) to a cold 100 K system would certainly be important (q/T = 10 J/100 K= 0.1 J/K) while the same amount of 10 joules spread out from different surroundings (just infinitesimally warmer than 1000 K) to a 1000 K system would be relatively trivial. (q/T = 10 J/1000 K = 0.01 J/K)
Now, you
know that a hot pan will cool down if the room is cooler than the pan -- we started with that -- it's our lifetime experience -- it's what we called the second law and we interpreted it as energy spreading out if it can. But is there any quantitative way that we can show that the second law "works"? Yes! That's where the power of entropy comes in! Entropy measures energy's spreading out; the larger the entropy increase, the greater the spreading out and the more probable is the event. Just look at that preceding paragraph: If a 1000 K and a 100 K system are in contact and 10 joules of motional energy were allowed to flow from one to the other, which direction would the energy flow? Only if energy flowed from the 1000 K system to the 100 K system would there be
any entropy increase -- (the calculation that you will learn from your text and class is not as simple as the arithmetic for the reversible transfer in the preceding paragraph, but the
direction of the process is adequately indicated by that easy arithmetic.).
So entropy increases when "heat" (transfer of energy) spontaneously flows from something hot to something colder. (Same as "entropy change is positive in sign.")
Q : So that's all?? Just hot pans cooling down again? And that one little q(rev)/T is entropy change?
A: ALL? HOLD IT now!! That's just like your question "Is that all?" when we first talked about the second law. And then we went on to see the amazing implications of the second law -- that it's the greatest generality in all of science -- that it's incredibly important for your understanding of how the world works -- that it's the greatest good and baddest bad for your own being alive. Ya can't have anything more important than that! Exactly parallel, entropy is of enormous importance in ANY serious understanding of chemistry and chemistry is central to everything in this universe.
The words and meaning of "entropy" and "second law" are so closely related (entropy being the quantitative measure of the qualitative law) that they are often used interchangeably. Never never forget that entropy MUST always be connected with ENERGY in general, and specifically with ENERGY that is being or has been dispersed.
[Entropy is more fully discussed in http://2ndlaw.oxy.edu/entropy.html . In the Appendix to the site you are now reading (accessible from the Last Page) are given some details of processes in which q is zero --i.e., the original ENERGY of the system is unchanged but it is more spread out over more volume; thus entropy increases. Those processes include a gas expanding into a vacuum, or two or more ideal gases or liquids mixing. An ideal solute dissolving in a solvent also involves no change in original ENERGY but the entropy of the solution increases because an added solute allows that energy to be more spread out.]
Q: You sure are yelling LOUD and long about energy being connected to entropy!
A: Absolutely!! THAT'S the big mistake that popular writers and even some teachers make about entropy. They've heard that antique erroneous statement about "entropy is disorder" so often that they too say that anything you can see in the world as mixed-up or messy is an example of an entropy increase. Nonsense. Total nonsense. You have to focus on how much and how widely is
energy dispersed in their examples. When and how and what kind of
energy got spread out has to be the first question in any example they talk about or we think about. Here, look at some horrible actual quotes.
In a textbook, there is a picture of Einstein's desk taken the day he died. Like most desks where scientists have been working hard, it looks messy. But the textbook says "Desktops illustrate the principle that there is a spontaneous tendency toward disorder in the universe..." Wow! Stay away from desktops -- you don't ever want to get caught by the scary spontaneous tendency that happens there! Here's a quote and a photo that really deceives a reader by the first four words that I've italicized: "
If left to themselves, the books and papers on the top of my desk always tend to the most mixed-up, disordered possible state." (And that was written by a scientist!) Wasn't he ever near that desk of his? Some mysterious alien force from outer space did it? Another, from a book about entropy that sold over a million copies: "Anyone who has ever had to take care of a house, or work in an office, knows that if things are left unattended, they soon become more and more disorderly..." Unattended means that nobody is around, doesn't it?. Isn't that writer implying that things all by themselves cause this disorderliness, rather than people? (He should be told that King Tutankhamen's tomb was left unattended -- really unattended -- for 3274 years and its arrangement of things was found to be seemingly unchanged, though dusty, when the tomb was finally opened in 1922.)
You get the point. The messy
appearance of a bunch of visible objects (and even the neat molecular order in an x-rayed crystal) have nothing to do with entropy. The only questions are "what is the energy process that made the objects that way? In what way was energy dispersed and how much energy change at what T occurred? In the usual dumb examples like those quotes in the paragraph above, it is in the
ATP of the muscles of the people who pushed the papers/books/clothes/pizza plates around where energy has been dispersed and so only there has the entropy increased.
Q: Why be so critical? Those writers just failed to say that they or somebody else was messing things up. What's this got to do with entropy?
A: That's not a minor omission! It's like a guy outside a bank telling you (as police were running toward you two), "Look at all this money that the nice bank teller shoved at me" and JUST FAILED TO SAY, "I had a gun pointed at him." Don't you think the gun had something to do with the money-shoving?
As I said a minute ago, reading statements like these in books gives many people who aren't as sophisticated as you a strange idea about entropy: it's a mysterious force that makes ordinary things jump around and is at work to mix up the world. That's total balderdash.. Every one of those authors was writing about the second law of thermodynamics and entropy
BUT "they left out the gun"!
That's most frequent error of scientific as well as popular writers -- even texts "leave out the gun" when they start talking about the ordinary world getting mixed up and "going toward disorder". It's people who mess up desks and dorm rooms (and much of the environment), it's hurricanes and tornadoes that tear houses and trees to pieces and scatter the bits; it's earthquakes that can even fracture a concrete freeway and topple a whole building. What's common to all those examples? Energy getting spread out, of course. Energy of ATP in human muscles, energy of air flow in hurricanes, energy of earth movement in earthquakes. As a result of those kinds of processes, solid things get scattered all over and mixed up. The objects do NOT,
by themselves, become disordered or random. There isn't any "tendency of objects to become disorganized" in nature any more than bank tellers have a "tendency to give money to robbers" -- without a gun.
Energy flow of many kinds is the driving force, the gun, for the world's macro objects becoming disorderly.
The reason so many authors make this mistake of saying "things are tending toward disorder" is their over-extending the basic behavior of
internally energetic,
mobile molecules and atoms all the way to totally immobile macro objects. We have already seen that those
microparticles at 1000 miles an hour clearly tend to be as random and disorderly as they can be. But if they are "boxed" in static
macro objects, whether in the stones of an Egyptian pyramid, or in the cardboards of a card deck in Los Vegas, or in the clothes and books and papers in a dorm room, they can't magically move those whole "boxes" they're in! Solid things, whether cards, stones or clothes, will stay exactly in the place that they are, at any moment in time, unless some adequate* energy flow
from outside them forces them to move a little or a lot.
If the initial arrangement of things was in some pattern or orderly, when the things are forced to move they will be pushed to different places and become more disordered.
Things don't have any tendency in themselves toward macro disorder; the energy flow that moves them is the cause of disorder. That's no indication that nature "doesn't like order". It's just that statistically there are many more billions (or quadrillions) of arrangements that are what we call "disorderly" than there are of the few dozens or hundreds that we call neatly patterned. A technical statement would be:
Whenever an adequate* amount of energy flows through a system of objects, it tends to scatter them. (The energy flow, if adequate*, can break bonds and disperse the resulting object parts.) They will be strewn to random, statistically probable locations consistent with all applicable factors of the objects and their flight paths or those for their fragments. In this process the concentrated energy in the energy flow becomes spread out or dispersed in imparting kinetic energy to the objects; its entropy is increased by such spreading out. Unless the original objects (or an appreciable part of them) are ground into a fine powder, their energy and their entropy contents are essentially unchanged a short while after the process of movement and scattering has stopped. (This time period allows any temporary heating effects to come to equilibrium with the local atmosphere after the energy flow ceases.)
*"Adequate" here means coupled (of the type and frequency that can interact with the object, necessary) and large enough to disrupt the existing arrangement of the object in its locale (sufficient).
Maybe the most dramatic example possible is what happens in a violent windstorm. After a tornado or a hurricane has devastated a town, the shattered houses and scattered wreckage are tragic sights. In seconds powerful winds have made random the most treasured and complex patterns that individuals have carefully created over many years. Ironically, the entropy change is not in all the shocking visible devastation. It is not in the destruction of our human patterns, not in
their change from orderly things to disorderly things. The thermodynamic entropy change is invisible in the sense that it is in
the dispersal of energy from the concentrated energy source -- the awesome whirling winds that have just passed have spread out some of their kinetic energy in spatially moving objects (an entropy increase in the winds) along with a lesser decrease (energetically) in temperature due to making the previously relatively calm air of the town more turbulent and it is slightly warmer.
Q: I get it. It's "adequate" energy flow that hits things and shoves them around to look disorderly -- things don't do anything like that by themselves. But wait a minute In some class or other I heard the prof say "everything is going downhill to maximum entropy, to chaos and disorder"
A: Some profs say weird things! That's a century-old misstatement that may sound profound but actually is just plain ignorant. It's like he took your class to a horse show but let you look only at the rear ends of the horses. Let's look at the rest of the horse instead.
You know all about the second law, how it says that spontaneous reactions "go downhill" -- meaning that they all spread out energy, and so entropy is always increasing. (Because entropy measures how much energy disperses at a specific temperature, T.) So in all such processes, sometimes the energy spreading out is "adequate" to push things around a little or a huge amount. Maybe we think that's undesirable disorder, or maybe it's obviously disastrous destruction.
Stop there a minute! Tornadoes and hurricanes in the US
are often horrendous -- their powerful energy flow certainly causes chaotic wreckage, especially in towns or cities. What's the source of that energy flow? It's energy from the sun hitting different kinds of the earth's surface, including oceans (where water is evaporated, rises to high altitudes and forms clouds). Because of the earth's varied surfaces, that solar energy heats the air near them differently, so the rising air moves at different rates. Energy dispersing; entropy increasing. We feel that as slight breezes or even strong winds blowing here and there. Is that bad? (That's somewhat "disorderly" but not really "chaos" or there wouldn't be any meteorologists and TV weather people!) Occasionally in the US, powerful colder winds from northern regions collide with equally fast-moving warmer moist air from the south and for a few hours tornadoes are formed here and there. Not good at all.
But compare the number of those undesirable events with the uncountable days of normal flow of moist air with clouds that bring rain to different regions of the US! Those many many days of rain all over the continent (and all continents) -- caused by "adequate" solar energy pushing millions of tons of water from the oceans up in the air -- is absolutely essential for plant life. Are growing plants -- from wheat and corn to flowers and trees -- undesirable "chaos and disorder"? And that's just one facet of the
good that the sun does -- sending to the earth only a billionth of the huge quantities of its energy it disperses per second -- even though, thereby, causing an enormous increase in entropy
in the sun as well as a tiny fraction of that entropy increase on the earth. However, we must always be aware that the most sensational downhill spreading out of solar energy (entropy increase) is the small fraction that is coupled with the uphill process of photosynthesis. Our whole lives -- almost all life totally depends on that capture of solar energy as it disperses.
[[There is more readable information about energy coupling in biochem toward the end of http://2ndlaw.oxy.edu/obstructions.html and by clicking on "Photosynthesis" near the end of the http://entropysimple.oxy.edu introductory page.]]
And that "uphill"aspect of the second law -- coupled with activation energies that protect systems from going back "downhill" energetically -- is what most professors who are not in science simply don't realize.
Q: Hey! I get it -- that's the end of the horse that they don't know about because they don't know chemistry: "The second law is our "greatest good"! You said all that back on page five.
A: Sure did. Glad you realize that big idea from science.
Think what a wonderfully different place the earth is today, compared to what it was a billion years ago when it was truly chaotic and disorderly. "Everything going to hell in a handbasket", some profs say? Activation energies hold the handles of that "handbasket" so everything
doesn't go to hell in so many instances! Today, full of amazing "uphill" plant life and "uphill" life of all sorts plus all the beneficial human-created order in small and large things, the earth is a remarkably better place than as the hot hunk of matter it began.
A major reason that our present physical world is deteriorating, of course, is human over-reproduction and overconsumption that results in the degradation of our environment. But those problems aren't due to some inexorable mysterious force or the Silent Sinister Subtle Scheme of entropy! It is we who are causing them.
It is true that the sun is decreasing in mass as thousands of tons per second are changed into truly huge amounts of energy. The sun is "going downhill" but it will take more than four billion years to get to that hill's bottom. That's a pretty long time off. I'm a lot more worried about the next fifty or hundred, aren't you?
Q: Sure. The next two. I have a feel for entropy. But why did you go into such a big song and dance with that jagged diagram a while ago just for busting a surfboard, skateboard, snowboard or ski??
A: Add "or for a car fender, jet engine blade, freeway bridge, leg bone, spine, or skull"!! Doesn't that mean you?! That diagram covers breaking an enormous span of solid things that really are important to us. So, it is a pretty big deal for our understanding bad things that can happen in our lives.
See that arrow, the E
ACT SOLID on the diagram? That represents a function which is equivalent to the E
a that starts chemical changes, chemical reactions like burning cellulose and rusting iron. The E
ACT SOLID is the activation energy that has to be applied to any solid object to start a physical change., its fracture. So the powerful new idea we have here is that both for chemical changes like fires AND for physical changes like breaking things, there is a minimum amount of energy, an activation energy, that is required to initiate the process.
With that new idea we can broaden our previous statement about activation energies in chemical reactions being obstacles or hindrances to chemical change. (As we've said, all of the organic compounds in our bodies could immediately catch fire in the oxygen of air if there weren't such obstructions to the second law as E
a.) Energies of activation in solids, E
ACT SOLID, similarly prevent solid objects from being broken readily. ("Wear" in solids is breaking off clumps of atoms so the E
ACT SOLID is very very important in thinking about tires or gears or bearings or anything wearing out. When things don't
wear out very fast, it means that inherently they have relatively high activation energies against fracture occurring.)
(Actually of course, as we talked about before, it is the resistance of chemical bonds to being broken that is reflected in the energies of activation. Thus,Eaand EACT SOLID are indicative or derivative functions -- i.e., they are due to a number of factors involving chemical bonds but they can be used as shorthand or symbols for resistance to change.)
Q: So what?
A: So everything! Here comes the big payoff: How knowing about the second law and activation energies can make a big difference in our understanding bad things that happen to us.
People from the beginning of history have worried about material things going wrong in their lives. About why bones break, why shiny copper jewelry (valuable in antiquity) turns green, why tools wear out, why rivers of mud rush down the hills and wreck the village, why people get sick, why they die. Fate and karma and spiteful gods have been just a few of the infinity of inaccurate solutions to the threatening problem of seemingly erratic nature. "Why me?" has probably been a human feeling before the invention of language. It is common today in any catastrophe. Is it justified?
You now know the basic cause of every material/physical event that we think is bad: It is the second law or, more accurately, what the second law describes: the behavior of energy in our real world. All the structures that we prize -- from our own bones to our artifacts like chairs or houses, skyscrapers, bridges or jet planes -- are subject to being broken or destroyed by adequate energy flow moving from being concentrated to becoming spread out and diffused. The distressing results of forceful impacts on bones and cars and buildings are simply manifestations of this tendency of concentrated energy.
(Quakes and violent winds are temporary and coincidental accumulations from less concentrated energy sources).
Further, you know now that all the chemical catastrophes that hit us are similarly caused because the substances involved in the disaster obey the second law. Whether forest fire, or Hindenburg fire-explosion, or dangerous corrosion of a car part, blocking of brain patterns by Alzheimer's factors, or bacteria that interfere with a critical feedback system in the body -- these are just examples of concentrated energy spreading out contrary to our human preferences.
As one of our major goals, we humans want order and organization of many different varieties. An equally important goal is our desire (not realizing the potential dangers) for oxidizable substances like wood or iron to use in our artifacts and like gasoline for always-safe power source in our machines. Neither goal is consistent with the second law. Yet we are surprised when, against our naive wishes, the predictions of the law actually come about. Murphy's Law (speaking only of matter-related events) that things always go wrong fits an emotional human need when we are frustrated; it’s a joke because it is such a gigantic exaggeration.
However, we may subconsciously let its humor make us concentrate on things going wrong and blind us to the most amazing fact in our second-law world:
Usually things do NOT go wrong. There are three major reasons that they don't: First, constant human care and caution in protecting against second law predictions. (Two mundane examples: planning and actions that reduce the possibility of fire in industry and the home, painstaking design for safety and the continued careful inspection of airplanes.) Second, the existence of activation energies that obstruct and block chemical processes or fracture of materials from occurring spontaneously (i.e., “blocking” the second law from milliseconds to millennia). Third, the literally incredible organization in living things: All the complex energy-processing systems -- from simple amebas to humans, from primitive grasses to complex plants --live and procreate because they are protected from failure by an enormous variety of feedback mechanisms.
(It is often the failure of only one activation energy out of billions, or one feedback loop out of thousands, that makes Murphy's Law seem valid. Fancifully, Eas and feedback cycles act as our ‘protectors’. Thus they could be called Maxwell's Angels (in contrast to that humanly-unhelpful “Maxwell’s demon”.)
A fractured leg in a ski accident, a spark in the fuel tank of TWA Flight 800, a broken timing gear in a Corvette, a fire in a fraternity house started by a forgotten cigarette, a California freeway collapse in an earthquake, a fall from a horse that results in a broken spine and quadriplegia -- all these are examples of activation energies being exceeded, whether in chemical reactions or physical fractures. Together with the thousands of illnesses that can destroy our functioning as whole persons, they constitute "things going wrong" in people's lives.
But activation energies that obstruct undesirable chemical and physical events almost always protect us and our prized objects even from disastrous change that the second law predicts. Bodily feedback systems almost always protect us from bacterial attacks and malfunctionintg human biochemistry.
Almost always.
Shouldn't "Why
me?" be our near-constant question of wonder and delight at being alive and being able to move and think and create -- in a second-law world that favors dispersed energy and inert sand? Knowledge of the second law makes unrealistic the human cry of "Why me?" that is so frequent at times of tragedy.
At such times, the only rational response is "Why
not me?", even though then it is emotionally quite unacceptable.
[Links and References follow below] Addendum: The Importance of Chemical Kinetics
"Time's Arrow", our psychological sense of time Philosophers and novelists and their readers have been disserved by hearing statements of the second law (that events and physical matter move in the direction of energy dispersion) without the essential codicil from chemistry that the law is continually blocked by activation energies.
Chemical kinetics (chemical dynamics) is the area of chemistry that focuses on activation energies and the rates of chemical reactions.
Physicist Arthur Eddington's maxim about the second law is an incomplete view of the way the world works without a chemist's correction : --
(AE, 1925) The second law of thermodynamics is time's arrow
(FLL, 1996)
but chemical kinetics is time's variable clock.
Or (FLL, 1998):
Chemical kinetics firmly restrains time's arrow
in the taut bow of thermodynamics
for milliseconds to millennia.
As a result of my suggestion, Professor Keith J. Laidler in his "To Light Such A Candle" (Oxford, 1998) says it profoundly at the end of his chapter on thermodynamics:
The universe as we know it is therefore as much controlled
by the laws of chemical dynamics
as by the laws of thermodynamics.
Links
- http://http://shakespeare2ndlaw.oxy.edu, a site primarily for students or adults in the humanities and arts. A summary of what C. P. Snow should have said about the second law and activation energies to his audiences when he mentioned thermodynamics. Some of the ideas in secondlaw site, but omitting entropy.
- http://entropysimple.oxy.edu, a more complete description of the second law and its implications for the ecology (weather patterns, photosynthesis, etc.) of the earth as well as the benefits of the second law for humans. Less informal than secondlaw site. Primarily for adults interested in the subject rather than students taking chemistry courses.
- http://2ndlaw.oxy.edu has five parts.
| The first, "Entropy and the second law of thermodynamics" gives a superior introduction to entropy from the standpoint of molecular behavior ("molecular thermodynamics") and quantized microstates, but does not introduce math or quantum mechanics. |
| The second, "The second law of thermodynamics is a tendency" is almost a repetition of material from secondlaw site. |
| The third, "Obstructions to the second law make life possible" develops the concept of activation energies as does secondlaw site but goes further in showing the relationship of endothermic reactions to energy input, including some material on substances found in space: how they could arise. |
| The fourth, "The second law of thermodyamics and evolution", responds to many questions sent to secondlaw site by individuals who did not realize that the second law energetically favors the formation of more complex compounds from the simple elements. |
The fifth, "Entropy and Gibbs free energy", is only for chemistry students, whereas all preceding material was for science and for non-science majors. The page really should be named "The Gibbs equation is ALL entropy!" – just to surprise chem students who have to work with it.)
|
- http://entropysite.oxy.edu is primarily for chemistry instructors
References
Please send your favorites to
entropy.lambert@gmail.com for future versions.
"Entropy Analysis", N. C. Craig, John Wiley: New York, 1992.
"The Second Law", H. A. Bent, Oxford: New York, 1965.
"To Light Such A Candle", K. J. Laidler, Oxford: Oxford, 1998.
"Note on Entropy, Disorder and Disorganization", K. C. Denbigh,
Brit. J. Phil. Sci.,
1989,
40, 323-332.
| "Why Don't Things Go Wrong More Often? Activation Energies: Maxwell's Angels, Obstacles to |
| Murphy's Law", F. L. Lambert, The Journal of Chemical Education, 1997, 74 (8), |
| 947-948. [link] |
"Chemical Kinetics: As Important As The Second Law Of Thermodynamics?", F. L. Lambert,
The Chemical Educator,
1998,
3 (2) [
link]
| "Shuffled Cards, Messy Desks, and Disorderly Dorm Rooms – Examples of Entropy Increase? |
| Nonsense!", F. L. Lambert The Journal of Chemical Education, 1999, 76 (10), |
| 1385 – 1387. [link] |
"Disorder -- A Cracked Crutch for Supporting Entropy Discussions", F. L. Lambert
The Journal of Chemical Education,
2002,
79 (2), 187-192. [
link]
"Entropy Is Simple, Qualitatively", F. L. Lambert,
The Journal of Chemical Education,
2002,
79 (10), 1241-1246 [
link]
""Order-to-Disorder" for Entropy Change? Consider the Numbers!". E. I. Kozliak and F. L. Lambert,
The Chemical Educator, 2005, 10 , 24-25. [
link]
courtesy:
http://www.secondlaw.com
For instance, you've heard about the dangers of nitroglycerin, a liquid that explodes violently just from being shaken hard or jarred sharply. Do you think that its energy diagram would look like the one for cellulose above? Of course not. It must have a very low activation energy, Ea. That leads to an extremely fast formation of hot gaseous products, an explosion (despite the relatively smaller difference in energy between "nitro" and the products). Explosives form hot gases so rapidly because they all have oxygen atoms as part of their molecules. Thus, those molecules don't need to wait until some molecules of atmospheric oxygen happen to hit them -- the way most substances have to do. Alfred Nobel was driven to invent a safer explosive when four workers and his brother were killed in the family nitroglycerin plant. He made what he called "dynamite" when he mixed oily nitroglycerin with some powdery silica material to form a seemingly dry solid that could be pressed into stick shape. They didn't detonate just from being hit or dropped. Obviously, therefore, an energy diagram for dynamite must look like the dotted line, a considerably higher Ea indicating that more energy must be put in, e.g., by a blasting cap, to initiate the spontaneous decomposition of the nitroglycerin. (TNT, used in armor piercing shells, is about six times more resistant to shock than nitroglycerin. Thus, you can guess at TNT's activation energy for reaction.) Dynamite has been mainly replaced by other explosives for excavation, etc., today. 