A Darke County Tale

First, permit me to describe myself. Despite the simplicity of
my form, I am complex. Only two atoms of hydrogen and one atom of
oxygen make up all of me. Without meaning to sound boastful, I
would say my personality is magnetic even electrifying! My oxygen
atom’s center, called the nucleus, carries eight positive
electrical charges. Eight negatively-charged electrons rapidly
orbit the center. They form four parts. Every pair sticks together
because the two electrons are spinning in opposite directions on
their own axis, generating a magnetic attraction. The four pairs
repel one another and keep far apart.

My two hydrogen atoms are much smaller than my oxygen atom like
two grapes next to a grapefruit (only on an atomically-tiny scale).
The center of each hydrogen atom (called a proton) bears a positive
charge. Opposites attract. Thus, two of the four negatively-charged
electron pairs grab fast to the two positively-charged hydrogen
centers. The angle between my hydrogen atoms is just about 104
degrees.

The hydrogen proton is tiny; it can come close enough to the
ample numbers of electron pairs of other water molecules to create
additional bonds. (For that matter, each of the two hydrogen atoms
contributes an electron of its own.) You see, because my hydrogen
atoms connect to my oxygen atom at an angle less than 180°, one
side of me is slightly more positive, the other side is a tad more
negative. My positive side attracts the negative parts of other
water molecules. So two or three or more water molecules can string
themselves together. Even as weak as these hydrogen bonds indeed
are, they make water a liquid, instead of a vapor (or
gas), at ordinary temperatures on earth.

In a barrel of water, the hydrogen bonds keep forming and
breaking down so that not all of the molecules are attached to
other water molecules at any one time. Generally speaking, the
hotter it gets, the faster I and my fellow molecules move and the
hydrogen bonds linking us molecules can break. Then I fly off by
myself as vapor. I don’t need a high temperature to do this,
but higher heat speeds up the process.

You probably have strolled out on the surface of a frozen lake
in winter. Beneath the solid ice is liquid water, and above the ice
if vapor. As you can recognize, water can exist in all three states
at once: solid, liquid, and gas. For comparison’s sake, iron is
solid until heated to 2,795°. It then becomes a liquid up to
5,432°, when it finally transforms into a gas.

Petroleum is the only other naturally-occurring liquid compound
existing in millions of tons on earth. But there is a billion
billion times more water than petroleum! Even you are seventy
percent water!

Now, on to my great adventure!

In July, I was happily minding my own business in a friendly
string of water molecules in a well in Darke County, Ohio, when I
found that I and about four hundred gallons of water had been
pumped into a tank on wheels. This water wagon transported me and
my companions across a grassy field. Then about half of the water,
including me, was pumped from the first tank into a second one.
When my friends and I happened to pass near the metal walls of our
new enclosure, I felt warmer than when I had been lying in the cool
well (where the temperature varied only about ten degrees year
round and only one degree per day). The hydrogen bonds in my string
held firm, nonetheless.

Without warning, I surged forward (pumped again! this time by a
geared pump). I rushed along a feed-water pipe and into a closed,
steel-shell heating mechanism. Here, I passed alongside tubes which
radiated so much heat that my temperature skyrocketed from about
65° to 150°. (Before long, I would be passing through the inside of
these same tubes but not until many amazing changes had
occurred.)

It all happened so fast that it’s only now that I have had
time to sort it all out. Just when I thought I’d reach 200°, I
was forced inside a boiler. The fiery heat thrilled me with a vague
sensation of explosive possibilities. As you know, heat is both a
quality to be felt and a quantity of energy which can do work.
Water 1,350 pounds of it was boiling in this flange-steel
cylindrical container measuring twenty-eight inches in diameter,
about seven feet in length, and ⁹/₃₂ of an
inch in thickness. The potential for dynamic energy could be
described only as tremendous. Thirty-six seamless-steel tubes, each
two inches in diameter and 84 inches long, were conducting 400°
combustion gases from a coal fire in a firebox in back of the
boiler barrel to a smoke box and smokestack (or chimney) in front.
These gases were chuffing through the tubes in a pulsating draft of
up to eight chuffs per second. Those tubes exuded terrific heat,
and, as we strings of water molecules churned around them in quick
currents, we grew hotter and hotter and hotter!

The weak hydrogen bonds attaching me to my companions broke
sooner than I had expected. I was suddenly free in the state of
vapor, also known as steam. (Not all of my friends in the
half-ton and more of water changed from liquid to gas so
rapidly.)

Allow me to pause here long enough to explain a matter of great
importance in light of what will follow. Out in the open air at
approximately the level of the sea, a pint of water will evaporate
into nearly twenty-seven cubic feet of steam. To put this same fact
another way, I tell you that the steam from a pound of water at
atmospheric pressure expands 1,600 times its volume in the liquid
state. To transform liquid water to vapor requires enormous energy
despite the relative weakness of the hydrogen bonds linking water
molecules. Of all natural substances, water demands the most energy
to accomplish this transmutation from liquid to gas. The same
amount of energy to convert one pound of water to steam could melt
three pounds of steel or thirteen pounds of gold.

Back to my astonishing tale … When I abandoned the liquid
state to become a molecule of steam in that boiler, I did so
because I could draw on plenty of energy from the heat, which can
help to do the work of changing from liquid to steam by breaking
hydrogen bonds. But heat isn’t the only story here; there was
pressure, too. Once I was free, I wanted to fly far away from my
fellow steam molecules, just as I would have done, had I been
outside in the open air. But I couldn’t!

I bubbled to the rolling surface of the water and leapt into the
torrid space above, but the boiler shell imprisoned me. My
temperature was precisely 327.75°, signifying that the pressure
which I and my steamy colleagues were exerting against every square
inch of the inner surface of that boiler was exactly 85.3 pounds.
No wonder I hadn’t boiled at the usual 212° but at a higher
temperature the pressure inside was nearly six times greater than
that of the atmosphere outside (14.7 pounds per square inch at sea
level)!

I was invisible, dry, and rich with potential energy. I danced
madly into a dome, then through a pipe which led me up, over, and
down into a steam chest, where a sliding valve mechanism uncovered
an exit for me and my comrades. This channel (or port) took me
inside a cylinder nine inches in diameter and, as I would instantly
discover, ten inches in length.

The pressure felt intense, but something gave way. My friends
and I had pushed against a piston, which began to slide down the
length of the cylinder. Shortly after I and my peers had been
admitted to the cylinder, the port shut, cutting off the entry of
any additional molecules. Still, a fourth of a trillion-trillion of
us had made it in. If you were to count each one of us at the rate
of one per second, it would take you 500,000 times the age of the
universe to finish counting. We kept shoving that piston, relieving
the pressure little by little. A few of my comrades huddled more
closely together, reforming their hydrogen bonds and reverting to
liquid. They had quit their rapid motion and their frenzy to
expand. Why? Because they had yielded their energy to the rest of
us to help us to expand farther (by pushing the piston). It’s a
little known fact, but expanding steam requires a small input of
energy to expand. Consequently, a nearly-negligible amount of
liquid water will form.

Many, many more of my peers also returned to the liquid state
but for entirely different reasons. They became lethargic and
reconstituted their hydrogen bonds that is, they condensed
because they had approached the walls of the cylinder, which were a
trifle less hot than the temperature of the steam.

Evidently, moments before my entrance into this space, steam had
been exhausted from the cylinder through those tubes alongside of
which I had passed in the heater. This action of exhausting had
permitted the departing steam to carry off heat absorbed from the
inner surface of the cylinder, left wet with a clammy film of
liquid molecules sunk into lassitude. Those of the fresh steam
molecules who had come in with me and were nearest to this surface
imparted their energy to reheat the walls almost to the 327.75° of
the boiler steam. I felt that this loss was a shame. After all, the
energy given up to reheat the cylinder’s innermost metallic
skin could have been put to better use pushing the piston. What a
purposeless decrease in the efficiency of the machine I was in!

Anyway, an immense number of steam molecules reverted to the
liquid state, swirling as more and more mist while the piston
traveled farther and farther toward the end of the ten-inch-long
cylinder. The sliding of the piston had presented us energetic
steam molecules a portion of the room we had wanted for expanding
outward, but the work we had done in shoving that piston had
depleted much of our energy. Soon, many of us were pooped.

At that moment, the port where I had entered the cylinder opened
again, and I and my colleagues scrambled for it. Our combined
pressure seriously declined, and a great deal of re-evaporation
occurred. In other words, at the lowered pressure, the temperature
was plenty to cause liquid molecules to jump back into a frantic
boil as steam. I both pitied and deplored these molecules, most of
them the same ones who initially had yielded their energy to reheat
the metal of the cylinder’s surface, for they had not done an
honest day’s work in pushing the piston. They had gone from
steam, to liquid, and back to steam with the waste of misdirected
effort.

I had virtually no time to consider them, however, while I
dashed through the port and found that the passage led me in a new
direction. Later, I learned that more fresh, or ‘live’,
steam had entered the cylinder on the opposite side of the piston,
thus compelling it to undergo a return trip. Not all my comrades
escaped before the port closed again, and I am told that the
returning piston compressed them. I am sure they valiantly pressed
back against the piston and formed a cushion between it and the end
of the cylinder a noble deed. Those of us who had been exhausted
through the port carried off with us much precious heat energy from
the inner walls of the cylinder. I remained sweltering, but before
long I knew that I was inside the tubes of the heater and that
energy was being drained from many of my friends. I suddenly
understood that, from within those heater tubes, they were warming
the feed water on the exterior of the metal in the same way that I
had been heated at the outset of my wonderful journey toward and
through the cylinder. I chuffed my way out of the heater, through
an exhaust nozzle which launched me dizzily upward, and out the
smokestack.

The blast of us molecules as we were jettisoned from the nozzle
served to swell the draft up the smokestack, thereby assisting the
hot combustion gases from the firebox to flash from the back of the
boiler, through the fire-tubes, to the smoke box, and up the
chimney. In contact with the cooler air, I calmed down enough to
form hydrogen bonds with several of my comrades. I was liquid again
water spiraling high above the smokestack where the force of the
exhaust steam and the smoky draft propelled me.

Below stood a nine-ton, 50-horse-power Case traction engine. In
my own small way, I had helped to run that powerful machine. During
my odyssey, I had pressed that piston forward, its motion relayed
as mechanical energy to the spinning crankshaft and revolving
flywheel. I noticed a crowd of onlookers appreciating the spectacle
of steam-powered machinery from the storied agricultural past of
America. I felt proud. I had contributed in yet another way to the
positive quality of life on earth.

Released from the convection currents, my molecular friends and
I formed a droplet and fell, splashing on the nose of one of the
spectators Bob Rhode, I think his name was.

Sources

For factual information, this article relies upon many sources,
notable among them:

Boss, William. The Heath Book for Threshermen. Winnipeg:
Heath, 1908.

Case catalogues, parts lists, and manuals (all reprints).

Deming, H. G. Water: The Fountain of Opportunity. New York:
Oxford UP, 1975.

The Power Catechism. New York: McGraw, 1897.

Thurston, Robert H. History, Structure, and Theory of the
Steam-Engine. New York: Wiley, 1904. Vol. 1 of A Manual of the
Steam-Engine. 2 vols.

I am indebted to Dr. Charles E. Hawkins, professor of physics
and director of academic computing at Northern Kentucky University,
for valuable computations included in this essay.