EXPLAINING THE BEHAVIOR OF THE LOCH NESS MONSTER
The Loch Ness Monster, affectionately known as Nessie, has
been an object of curiosity since 565 A.D. Of the 500 freshwater
lochs (lakes) in Scotland, people have seen Nessie only in three
of them. It's interesting that only these three lakes are very
deep and each is surrounded by Scotch pines which are not present
around the other lakes. With these observations in mind, some
scientists have come up with the following theory.
Scotch pines have much more resin than other pines. If you
have ever had a Scotch pine Christmas tree, you probably noticed
that the presents under the tree become covered with sap. When a
Scotch pine dies and falls into a lake, it sinks to the bottom
and the wood releases its resin. The resin, clinging to the dead
tree, traps decomposition gases from the decaying wood. Trapped
by the resin, the gases form blisters on the tree. As the
blisters increase in size, they become large enough to buoy the
tree to the surface. Since water pressure is greater on the
bottom of the loch than at the top, the pressure on the blisters
continuously decreases as the tree rises to the top. Since
decreasing the pressure on a gas increases its volume, as the
tree rises to areas of decreased pressure, the blisters continue
to inflate. The more the blisters inflate, the greater the
buoyant force becomes, and as the buoyancy increases, the tree
rises faster and faster. Eventually the blisters burst and the
tree sinks quickly back to the bottom of the loch. Every once in
a while, a tree reaches the surface where it raises its "monster-
like" head out of the water before quickly diving again out of
sight.
Reprinted with permission. Adopted from articles written by
Ronald DeLorenzo appearing both in the Journal of Chemical
Education, July 1989, page 570, and in General Chemistry by Kask
and Rawn, 1993, page 376, Wm. C. Brown Publishers.
HEAVEN IS HOTTER THAN HELL
A study was conducted to determine the temperature of Hell.
The reasoning process used in the study is interesting because it
involves both the knowledge and the logic with which you should
be equipped.
The Bible (Rev. 21:8) tells us that Hell is a lake of fire
and brimstone. What is brimstone? Brimstone is sulfur. Sulfur
must be molten (liquid phase) since the Bible says it is a lake.
From this information, we can determine the temperature of Hell.
Start by looking up the melting and boiling points of
sulfur. If sulfur is present as a liquid, its temperature must
be somewhere between sulfur's melting and boiling points. The
boiling point of sulfur is 832 degrees Fahrenheit, and the
melting point is 246 degrees Fahrenheit. Since Hell is eternal,
it could not be at the boiling point for then it would quickly
evaporate. Most likely, Hell is about 246 degrees.
The same study also determined the temperature in Heaven.
The Bible (Is. 30:26) tells us that in Heaven the light of the
moon is as the light of the sun. Also, the light of the sun is
seven times the light of seven days on earth.
Heaven receives 50 times more light than the earth. Heaven
gets 49 times the amount of light from the sun relative to the
earth and an additional amount of light from the moon that equals
the amount of light we on earth receive from the sun. So, all in
all, Heaven receives 50 times more light than we do on earth.
Assuming that the temperature of Heaven remains constant,
Heaven must also lose by radiation 50 times as much heat as does
the earth. The Stefan-Boltzmann fourth-power radiation law
predicts that Heaven must be 977 degrees Fahrenheit if it were to
radiate this much heat.
Knowing that Hell could be about 750 degrees cooler than
Heaven may be a comforting thought for some of us.
Adopted from an article written by Ronald DeLorenzo
appearing in Problem Solving for General Chemistry, 1993, Wm. C.
Brown Publishers.
WHY DOES OATMEAL STICK TO YOUR RIBS?
Have you ever heard that "oatmeal sticks to your ribs"?
This adage simply means that after a breakfast that includes a
hot bowl of oatmeal, your appetite stays satisfied longer
throughout the morning than it would if you had eaten a
presweetened cold cereal or if you had eaten a less nutritious
item such as a candy bar or some cookies. Why is this so?
There are many reasons why oatmeal gives you a sense of
being full longer than presweetened cold cereals. One reason has
to do with heat calories. To illustrate, consider what happens
when you eat a bowl of cereal with cold milk. Let's assume you
use 500 g of cold milk (about one cup poured onto the cereal and
another glass of milk to drink). If your body temperature is
37.0 oC and the milk is 0.0oC, your body must burn 18,500
calories' worth of your breakfast just to warm the cold milk you
consumed with your cereal (remember that 1000 calories is 1 food
Calorie). If you had eaten hot oatmeal, you would have conserved
this energy, and the energy provided by the hot oatmeal would
have taken you that much further into your day before you once
again became hungry.
Oatmeal also sticks to your ribs longer than many cold
cereals because oatmeal is a complex carbohydrate, and complex
carbohydrates are more slowly broken down by your body than the
simple carbohydrates such as sugar that are found in ready-to-eat
presweetened cereals. In fact, some ready-to-eat cereals are
more than 50% sugar. Although simple carbohydrates may satisfy
your hunger by raising your blood sugar, your body digests the
simple carbohydrates so quickly that your blood sugar falls a
short while afterwards, and you are once again hungry. In
contrast, because your body digests the complex carbohydrates in
oatmeal more slowly, you retain a feeling of being full for a
longer period of time after eating oatmeal.
So, if you find that you are one of the many people who get
hungry way before lunch time, try making a hot bowl of oatmeal a
part of your breakfast. Prove to yourself that the combination
of the cereal's warmth and its complex carbohydrates really do
help the oatmeal "stick to your ribs."
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo appearing in Understanding Chemistry, An
Introduction by Dewey, 1994, page 58, West Publishing Company.
SPORTS DRINKS MAY NOT BE WORTH THEIR SALT
Since the 1970s, coaches have urged athletes to drink only
water or highly dilute sugar solutions while they exercise.
However many professional athletes and sports enthusiasts can
still be seen drinking commercial thirst quenchers that are
commonly referred to as sports drinks. Are sports drinks better
than ordinary water? Many studies suggest they are not. Because
of the presence of sugar and salts in these drinks, water in
commercial thirst quenchers remains in the stomach longer than
plain water does. In addition, sports drinks can actually cause
mild dehydration. Here's how that happens. Because sports
drinks contain sugar and salts with concentrations greater than
that of normal body fluids, they are said to be hypertonic.
Hypertonic liquids can cause dehydration by initially drawing
body fluids from surrounding organs into the stomach. This is
similar to the process that takes place when raisins are placed
in a glass of tap water and left overnight (see The Macon
Telegraph, November 2, 1993, page 5-D). Because the salt and
sugar concentrations inside the raisins is higher than that in
the tap water, the raisins draw in water and blow up like
miniature balloons. This process is called osmosis, and osmosis
can be fatal to people who drink ocean water in emergencies.
Because ocean water is excessively hypertonic, people actually
die from dehydration when they drink ocean water. Although
sports drinks are far less hypertonic than ocean water, they can
still dehydrate drinkers enough to decrease their athletic
performance. If you have been exercising, it's best to drink
plain water before, during, and after your workout.
Reprinted with permission. Adopted from articles written by
Ronald DeLorenzo appearing both in the Journal of Chemical
Education, February 1982, page 153, and in General Chemistry by
Kask and Rawn, 1993, page 478, Wm. C. Brown Publishers.
THE KILLER LAKE OF CAMEROON
On August 16, 1984, officials found thirty-seven people
laying dead along the roadside by Lake Monoun in the western
African Republic of Cameroon. Then, in 1986, the Killer Lake
struck again, this time taking 1746 human lives and thousands
more in livestock. The deaths were apparently caused by flooding
and suffocation. Scientists finally concluded that carbon
dioxide buildup in the lake caused the deaths. To understand
what had happened, let's first analyze the properties of carbon
dioxide dissolved in water, specifically bottled soda.
In addition to water, sugar, and flavorings, soda contains
dissolved carbon dioxide. While soda remains sealed under four
atmospheres of pressure (60 pounds per square inch), its carbon
dioxide stays in solution. However, when the seal is broken and
the pressure drops, the gas abruptly leaves the soda can or
bottle, and it sometimes causes liquid to leave as well.
The killer lake of Cameroon is similar to a can or bottle of
soda. Decaying animal and plant life at the bottom of the lake
provide a source of carbon dioxide. Since high pressure
conditions exist at the bottom of deep bodies of water, carbon
dioxide quickly dissolves into solution. As long as the carbon
dioxide remains under this high pressure, it stays in solution.
Because the waters of the killer lake of Cameroon exist in
stratified layers with very little mixing, its carbon dioxide
stays at the bottom in solution.
Under certain conditions the stratified layers may become
disturbed. Volcanic activity, a wind storm, or an earthquake may
cause the layers to mix. Such events could trigger an underwater
landslide along the steep slopes near the lake bottom. This
disturbance churned the bottom layer and carried it closer to the
surface where reduced pressure released the carbon dioxide into
the atmosphere. As the carbon dioxide erupted from the water, it
produced a 262-foot high wave that flattened plants along the
shoreline. Since carbon dioxide is heavier than air, it pushed
aside all air as it blanketed the ground. Those breathing the
carbon dioxide died from suffocation due to the absence of
oxygen.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo appearing in General Chemistry by Kask and Rawn,
1993, page 512, Wm. C. Brown Publishers.
HOW DO PEOPLE WALK ON FIRE?
Fire walking refers to an age-old practice in which people
walk across red-hot coals whose temperature exceeds 1000 o F
without pain or physical injury. The mystery of fire walking
exists primarily because many people confuse heat with
temperature. But there is a difference between these two terms.
You have probably done something very similar to fire
walking without even realizing it. In a hot oven, the oven air,
a pan in the oven, and the oven rack will all be equally hot
because they are all the same temperature. When you briefly
place your hands into the oven, the experience is painless.
However, if you were to pick up the pan or touch the oven rack,
it would burn you. Although the air, the pan and the rack are
the same temperature, the air in the oven contains less heat (it
has a lower heat capacity) than the pan or the rack. Your hands,
which are mostly water, can hold more heat than air (your hands
have a higher heat capacity). When heat flows from the hot oven
air over your hands, the hot oven air cools quickly. Since your
hands have a higher heat capacity, they warm only slightly.
Fire walkers use the same concept. The red hot embers and
pumice rocks that they walk across have much lower heat
capacities than the fire walker's feet. As heat energy leaves
the embers or rock, they cool down quickly, and the fire walker's
feet warm up only slightly. As a result, the experience is
painless. You should realize that fire walkers could not walk
across a 1000-degree hot steel plate for the same reason that you
could not pick up a hot pan from the oven. The steel plate has a
higher heat capacity than embers or pumice rocks.
There are several other reasons why fire walking can be
accomplished. One of these is the length of the fire bed.
Typical fire beds are only about ten feet long. Fire walkers
cross them in about two or three quick steps. A second factor is
that the embers are insulators, not conductors. Once cooled,
heat does not quickly flow into the cooled ember. Likewise, hot
oven air is an insulator while the oven rack is a conductor.
Warning: Without professional instruction, fire walking can
be dangerous. You should not try this on your own.
Reprinted with permission. Adopted from articles written by
Ronald DeLorenzo appearing in both the Journal of Chemical
Education, November 1986, pages 976-977, and in General Chemistry
by Kask and Rawn, 1993, page 18, Wm. C. Brown Publishers.
THE COLA SPACE WARS
In the presence of gravity, objects such as pencils have a
natural tendency to lower their energy by falling. However, in
the absence of gravity in outer space, pencils don't fall.
Dropped pencils float around and randomly disorder themselves
throughout a space craft.
In 1985, NASA made plans to test a special Coka-Cola can
on a space shuttle mission. Having a special soda can is
essential because drinking carbonated beverages is very difficult
to do in zero gravity. Then, not to be outdone, Pepsi introduced
their own specially designed can, and the Cola Space War began.
Pepsi's can relied on an arrangement involving an acid found
in fruit juice (citric acid) dripping onto baking soda to produce
carbon dioxide. (You are probably familiar with a similar
reaction between vinegar and baking soda which also produces
carbon dioxide gas.) The carbon dioxide inflated an inner pouch
forcing Pepsi out of the can through a special spout. There was
only one problem with the arrangement: citric acid, like
any object, doesn't fall without gravity.
The Coke can stored its soda inside a balloon. Pressure
from carbon dioxide outside the balloon forced soda out of the
balloon and out of the can through a specially designed spout.
The final testing of Coke's space can successfully took place in
1991 aboard the Soviet Space Station Mir.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo appearing in General Chemistry by Kask and Rawn,
1993, page 763, Wm. C. Brown Publishers.
PREDICTING THE NEXT CALIFORNIA EARTHQUAKE
Historians have recorded only two major earthquakes in
California, and both of those occurred when the state had a small
population. Now that California is the most populated state in
the Union, another major earthquake could be devastating both
economically and in terms of the loss of human life. Were the
California earthquakes quirks of nature or part of a regular
repeating series of earthquakes? If the latter is true, it could
lead to the prediction of the next major California quake.
Scientists excavated a 13-foot trench about 60 miles north-
east of Los Angeles. There they found places where the
sedimentary layers had shifted and separated at several
locations. The assumption is that each strata break of several
feet represents the occurrence of a major earthquake. By carbon-
dating the remains of once-living organisms at each of these
breaks, scientists determined the approximate time when each
earthquake took place.
From the activities of the organic matter in these separated
sedimentary layers, scientists have determined that the ages of
the organism remains ranges from 130 to 1410 years. We now know
that over the last 1400 years, major Californian earthquakes have
taken place about every 150 years. Since the last large
earthquake took place in California in 1720 (the 1857 and 1990
earthquakes were relatively tame), the next big quake has been
overdue for the last 130 years. Also, since the largest previous
interval between quakes was 275 years, Californians are probably
due for another one just about any day now.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo appearing in General Chemistry by Kask and Rawn,
1993, page 911, Wm. C. Brown Publishers.
DEGREASING POTATO CHIPS AND SALVAGING ABANDONED OIL WELLS
Just as bar magnets with north and south pole ends are
polar, some molecules have positively and negatively charged
ends. Molecules with charged ends are called polar molecules.
Molecules without charged ends are called nonpolar molecules.
Polar molecules such as water dissolve other polar molecules
such as alcohol. Similarly, nonpolar molecules such as oil
dissolve other nonpolar molecules such as iodine. Chemists
summarize this by saying that "like dissolves like." On the
other hand, polar molecules such as water do not dissolve
nonpolar molecules such as oil. That's why oil and water
separate when mixed together.
This premise of like dissolves like is used extensively by
chemists. Carbon dioxide has some unique properties that are
utilized by food and oil industries. Carbon dioxide molecules
are nonpolar. Although carbon dioxide is a gas, it begins to act
more and more like a liquid as its pressure increases. The food
industry uses high pressure carbon dioxide to remove oils from
food thereby reducing fat content and calories. For example,
potato chips are usually around 50% oil by weight. Since like
dissolves like, when carbon dioxide meets an oily potato chip,
the nonpolar carbon dioxide dissolves the nonpolar oil in the
potato chips. This removes some of the oil from the potato
chips.
In many instances, when oil companies abandon an oil well,
they leave much oil behind. Oil consists of many substances,
some more viscous than others, but all nonpolar. The oil that
oil companies pump from oil wells is the least viscous portion
which is easiest to remove. The remaining viscous oil is too
difficult and expensive to recover. One way to recover the
remaining viscous oil is to make it less viscous by pumping
carbon dioxide into the well. Since like dissolves like, carbon
dioxide injected into abandoned wells readily dissolves in the
viscous oil. Because the resulting solution of oil and carbon
dioxide is less viscous, it is easier to remove. There are more
than 300 billion barrels of viscous oil left in exhausted U.S.
wells. This translates into trillions of dollars for those who
recover this oil.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo appearing in General Chemistry by Kask and Rawn,
1993, page 257, Wm. C. Brown Publishers.
SAND CAN RESTORE EYESIGHT AND HEARING
Quartz, which is found in sand, and certain other crystals
exhibit the piezoelectric effect. Such crystals vibrate when in
contact with an electric current. This property has profound
applications in medicine.
The property of piezoelectric material to vibrate when an
electrical current is applied to it has a use in helping blind
persons see. Special eye glasses have been made that convert
light waves into electric signals. Those signals are sent to
piezoelectric material contained in a large patch measuring about
1´ feet by 1´ feet. The patch is worn by the blind person on
their backs. The piezoelectric material in the patch vibrates
when it receives the electric signals from the glasses. When the
patch receives the electric signals and vibrates, the vibrations
form a tactile impulse on the wearer's back. The first time that
someone wore the glasses and the piezoelectric patch, something
unexpected happened: the wearer thought he was seeing images in
his head. Somehow, the brain converted the tactile vibrations
from the patch into mental images.
When wearing this device, the blind have enough visual
capabilities to find articles in a room and read meters; they can
correctly identify wave patterns displayed on oscilloscopes, and
they can assemble objects as small as microcircuits.
A similar device exists for the deaf. Like the special
glasses for the blind, this device connects a hearing aid to a
piezoelectric back patch. The hearing aid converts sound waves
into electric signals and sends the signals to the piezoelectric
patch. The piezoelectric patch converts the electrical signal
into vibrations. Wearers are able to recognize broad sounds like
ringing bells and barking dogs as well as individually spoken
words and short sentences. Because there is no surgery involved
to install it, this tactile hearing aid is safer than some
alternative procedures.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo appearing in General Chemistry by Kask and Rawn,
1993, page 344, Wm. C. Brown Publishers.
THE AMAZING WATER DIET
According to medical specialists, the average American daily
diet is about 2500 Calories per day. (Nutritionists use a
capital C to spell the word calorie. Later in this box we'll
discuss the difference between a calorie and a Calorie.) This
means that the food we consume burns (oxidizes) in our bodies to
produce on average 2500 Cal of energy. Our bodies use these 2500
Calories to power the various biochemical reactions that keep us
alive.
Medical authorities recommend that the average American
drink six glasses of water each day for overall good health. Six
glasses of water equals 1.5 quarts or about 1.5 liters. The heat
from our bodies warms the water we drink until the water reaches
body temperature. How much heat would our bodies have to provide
to warm 1.5 liters of ice cold (0oC) water to body temperature
(37oC)? Calculations show that our bodies must burn 55,000
calories worth of food to warm the 1.5 liters of cold water.
Does this answer make sense? Does it make sense that each
day you consume enough food to produce 2500 Cal and can drink six
glasses of water that consumes 55,000 cal? What an amazingly
easy way to lose weight. Unfortunately, it doesn't work.
In the area of nutrition, a Calorie (with a capital C) is
what other scientists refer to as a kilocalorie (that is 1000
calories). The average American diet is actually 2,500,000
calories per day (2,500 kcal/day). This nutritional jargon of
referring to a kilocalorie as a Calorie is very confusing and can
lead to the type of misunderstanding that we have just
encountered.
One and a half liters of ice cold water does absorb 55,000
calories from our bodies, but that's only 55 kcal v. the 2,500
kcal supplied by our daily diets. However, drinking cold
beverages can be a worthwhile activity. Fifty-five kcal is
significant when we realize that we have to walk more than two
miles to burn fifty-five kcal of food or body fat.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo appearing in General Chemistry by Kask and Rawn,
1993, page 187, Wm. C. Brown Publishers.15.9.2
SOME INTERESTING CONSEQUENCES OF ACID RAIN
For centuries, acid rain has been responsible for
substantial environmental damage. Acid rain comes from many
sources, both man-made and natural. We primarily hear about
problems in North America, but the problems are worldwide.
One primary man-made source is the burning of fuel that
contains sulfur impurities. Along with the fuel, the sulfur
impurities burn to eventually form sulfur trioxide, and the
sulfur trioxide reacts with rain water to form sulfuric acid.
Other nonmetal oxides, such as carbon dioxide and nitrogen
dioxide, can react with rain water to form nitric acid and
carbonic acid. The decomposition of dead plants is one major
natural source of carbon dioxide. Volcanoes are another source
or carbon dioxide and other nonmetal oxides.
For centuries buildings and statues have been constructed of
marble and limestone. Both of these construction materials are
primarily calcium carbonate, which acid rain can dissolve,
thereby breaking down the very structures of buildings and
statues. In the United States, acid rain decays exterior
building stonework at an estimated cost of $2 billion/year.
Acids can also dissolve metals such as iron. A specific
example of this is the reaction of acid rain with iron in outdoor
bells in Holland. The acids in rain cause the thinning of the
bells' walls which changes their natural frequency and makes the
bells go out of tune. Smaller bells go out of tune faster than
larger bells. By filing down the larger bell's interior, their
pitch parallels that of the smaller bells.
A more serious problem occurs when acid rain affects our
drinking water. Acid rain dissolves toxic metals naturally
present in the soil causing them to be leached into drinking
water. Normally soil ties up many toxic metals as water-
insoluble compounds. But because these compounds dissolve in
acids, acid rain unties them. The resulting dissolved toxic
metals are now free to enter our drinking water supplies.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo appearing in General Chemistry by Kask and Rawn,
1993, page 73, Wm. C. Brown Publishers.
TRACING A BULLET'S PATH
The flight path of a bullet can be determined using neutron
activation analysis. When a gun is fired, small amounts of
gunpowder (containing carbon) are sucked along by the vacuum
created by the bullet. This forms a pattern on the ground as the
gunpowder falls. When a murder is committed, the area
surrounding the body can be irradiated with a neutron beam which
activates the gunpowder. The bullet path can be detected from
the activated gunpowder. Analysis of the activated gunpowder
also can determine the direction from which the bullet was fired,
roughly the distance traveled, and whether the ammunition was of
the rim or center-firing type. If the gunpowder contains a
tracer chemical, it is also possible to determine where the
ammunition was produced and sold (by neutron activation analysis
of the tracer elements present in the gunpowder).
Adopted from an article written by Ronald DeLorenzo appearing in
Problem Solving for General Chemistry, 1981, page 457, D. C.
Heath and Company
THE BIOLOGICAL CLOCK WITHIN US (CIRCADIAN RHYTHM) VERSION I
Let's assume that you live in Connecticut and that you
regularly awaken each morning at 7:00 o'clock. If you were to
fly to California today, you would probably still wake up
tomorrow morning at 7:00 A.M. Connecticut time even though it
would be 4:00 A.M. in California. Your body is able to keep
track of time, but its clock is still set to Eastern Standard
Time. A similar ability to keep track of time is also found in
animals, plants, and even in one-celled organisms. For example,
the one-celled algae living on Cape Cod, Massachusetts, bury
themselves in the sand just before the tide comes on Cape Cod in
and resurface when the tide goes out again. This behavior keeps
the algae safe from the rushing water, but it continues without
purpose even when the algae are moved many miles away from the
beach and placed in an environment that is always kept lighted
and held at a constant temperature. Even though they are now
safe from the tide, the algae will bury themselves and resurface
in synchronization with the tide cycles at Cape Cod.
Several years ago, scientists speculated that our metabolism
(the chemical processes that living things do to maintain life)
may be associated with an internal clock. To test this idea, the
scientists gave the deer mice mixtures of regular water and heavy
water (made of deuterium oxide). The scientists speculated that
the heavy water molecules would move and react more slowly during
metabolism and slow the internal clock. This is exactly what was
found: the greater the heavy water concentration, the slower the
biological clocks of the deer mice.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo appearing in Understanding Chemistry, An
Introduction by Dewey, 1994, page 109, West Publishing Company.
THE BIOLOGICAL CLOCK WITHIN US (CIRCADIAN RHYTHM) VERSION II
Let's assume that you live in Connecticut and that you
regularly awaken each morning at 7:00 o'clock. If you were to
fly to California today, you would probably still wake up
tomorrow morning at 7:00 A.M. Connecticut time even though it
would be 4:00 A.M. in California. Your body is able to keep
track of time, but its clock is still set to Eastern Standard
Time. A similar ability to keep track of time is also found in
animals, plants, and even in one-celled organisms. For example,
we can predict within 15 minutes when hamsters that are kept in
total darkness 24 hours a day will get on and off their exercise
wheels, even though these hamsters are kept perfectly isolated
from all external clues of time passage. Potatoes consume more
oxygen in the day even when they are kept in light-proof
containers that are held at a constant temperature and pressure.
Perhaps even more amazing is the behavior of the one-celled algae
living on Cape Cod, Massachusetts. These tiny organisms bury
themselves in the sand just before the tide comes on Cape Cod in
and resurface when the tide goes out again. This behavior keeps
the algae safe from the on-rushing water, but it continues
without purpose even when the algae are moved many miles away
from the beach and placed in an environment that is always kept
lighted and held at a constant temperature. Even though they are
now safe from the tide, the algae will bury themselves and
resurface in synchronization with the tide cycles at Cape Cod.
Similar observations have also been made when various organisms
were sent into outer space where they were even further removed
from terrestrial time clues such as the earth's rotation.
To understand how all life-forms are able to keep accurate
track of the time within minutes per day, we need to ask how we
ourselves consciously measure time. We measure time against
recurring events that take place at a constant speed such as the
spinning of the earth on its axis (once per day) or the
revolution of the earth around the sun (once per year). Then we
must ask ourselves what it is that all life forms have in common,
from complex humans to simple one-celled algae organisms, that is
recurring and that takes place at a constant speed.
Several years ago, scientists speculated that our metabolism
(the chemical processes that living things do to maintain life)
may be associated with an internal clock. To test this idea, the
scientists used isotopes to tinker with the living clock within a
group of deer mice. Before we can understand the role of the
isotopes, let's first examine how isotopes of the same element
are similar to each other and how they differ from each other.
Isotopes of the same element are chemically identical but
physically different. For example, hydrogen (1H) and deuterium
(2H) both react chemically with fluorine. The former produces
hydrogen fluoride and the latter deuterium fluoride. However,
because deuterium is twice as massive as hydrogen, deuterium
atoms and molecules move much more slowly. In fact, the reaction
between hydrogen and fluorine takes place so rapidly that the
reaction is explosive, but the reaction between deuterium and
fluorine is non-explosive.
Knowing this difference between isotopes, scientists gave
laboratory deer mice a mixture of water made with hydrogen (1H2O)
and deuterium (2H2O). We will refer to these two forms of water,
which appear identical to one another, simply as normal water and
heavy water. Because of its greater mass, however, heavy water
chemically reacts slightly more slowly than normal water in
metabolism processes. As a result, it was expected that the
speed of the deer mice biological clocks would vary inversely to
the heavy water concentration they drank. This is exactly what
was found: the greater the heavy water concentration, the slower
the biological clocks of the deer mice.
Today we believe that the core of the biological clock is
associated with the production of a specific protein. When the
concentration of this protein is high, organisms shut down the
production process for that protein. Then, when the protein
concentration decreases below a certain pre-established level,
organisms turn the production process back on again. As a
result, the concentration of this protein peaks and wanes with
fairly precise regularity every 24 hours, and this is now thought
to be the recurring, constant speed event used by living cells.
A clear understanding of how isotopes differ allowed
scientists to originally determine how living organisms tell
time. Scientists are currently linking aging problems such as
sleep disorders with the erroneous workings of our biological
clocks, and they are hopeful that a better understanding of these
clocks will lead to a better comprehension of other mental
processes in the not-to-distant future.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo appearing in Understanding Chemistry, An
Introduction by Dewey, 1994, page 109, West Publishing Company.
EXPLODING CAR BATTERIES
The tragic detonation that destroyed the Hindenburg, a
hydrogen-filled dirigible, was caused by the explosive
combination reaction between hydrogen and oxygen. More recently,
this same combination reaction took the lives of all American
astronauts aboard the space shuttle Challenger. Although many
are familiar with these two events, few are aware of a more
common hydrogen-oxygen explosion that causes about 6,000 eye
injuries each year in this country: exploding car batteries.
During the normal operation of your car, electricity
produced by the alternator produces a chemical reaction inside
the battery that decomposes water into hydrogen and oxygen
gasses. Therefore, it is important to keep open flames and
sparks away from these batteries. Because car batteries also
contain sulfuric acid, a hydrogen-oxygen explosion can propel
this caustic acid along with battery case fragments into the eyes
of bystanders. It should be obvious that it is dangerous to
smoke while working under the hood, and it is even more dangerous
to use a cigarette lighter or a match at night to illuminate a
car battery to check its fluid level. Less obvious, however, is
the explosion danger when incorrectly jump-starting a dead car
battery. If you fail to follow the directions in your owner's
manual for properly jump-starting your car, you will likely
produce a spark between the jumper cable and the car battery.
This spark can ignite the hydrogen gas inside a car battery.
Because so many car batteries die in cold winter weather, this
season is when most of these explosions occur.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo appearing in Understanding Chemistry, An
Introduction by Dewey, 1994, page 470, West Publishing Company.
ACID SNOW
You have probably been hearing about acid rain in the news
for years. Have you ever heard of acid snow? Some experts
believe that acid snow is even worse than acid rain. Before we
see why, let's first take a look at acid rain, what causes it,
and why it's harmful.
Acid rain is considered to be a serious pollution problem in
most industrialized nations including the United States. In this
country alone, acid rain has caused hundreds of lakes to become
fishless because fish cannot survive if their water is too
acidic. Also, each year, acid rain causes tens of billions of
dollars worth of damage to buildings and statues because acids
readily react with marble, limestone, and metals.
Acid rain comes from many sources, both man-made and
natural. One primary man-made source is the burning of fuel that
contains sulfur impurities. Along with the fuel, the sulfur
impurities burn to eventually form sulfur trioxide, and the
sulfur trioxide reacts with rain water to form sulfuric acid.
Other gasses such as carbon dioxide and nitrogen dioxide can
react with rain water to form acids also. The decomposition of
dead plants is one major natural source of carbon dioxide.
Volcanoes are another source of carbon dioxide.
But, as we said earlier, there may be something even worse
lurking out there: acid snow. Both acid snow and acid rain form
the same way. After gasses react with water in the atmosphere to
form acids, the acids may come down in many forms including
sleet, hail, rain, and snow. There are at least two reasons why
acid snow is considered to be worse than acid rain. First, when
acid rain falls, it does its damage gradually over a period of
several months. However, in some parts of the country, when acid
snow falls, it sits on the ground until Spring before it melts.
Then, an entire season's worth of snow is released into the
environment in one brief period, thereby doing more damage.
Second, acid snow melts in the spring when new life is emerging,
and new life is most vulnerable to toxic conditions.
Although acid rain poses a serious threat to our global
environment, northern regions may suffer even greater damage each
spring when an entire season of acid snow melts and enters the
biosphere at once.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo appearing in Understanding Chemistry, An
Introduction by Dewey, 1994, page 441, West Publishing Company.
PRESIDENTIAL ASSASSINATION THEORY AND HAIR ANALYSIS
Scientists use neutrons to determine which chemical elements
are present in unknown samples and how much of each element is
present. When bombarded with neutrons, elements in the treated
sample absorb some of the neutrons and become radioactive. Each
radioactive element emits its own characteristic radiation, and
by making careful measurements to determine the type of radiation
being emitted, scientists can determine which elements are
present. Since the intensity of radiation depends only on the
amount of radioactive material present, it is also possible to
determine how much of each radioactive element is present in the
unknown sample. If the unknown sample is human hair, much
information about the person can be deduced. Your hair is a
living diary because that's where your body deposits all
chemicals that you have ever taken. If you drank soda from an
aluminum can last week, your body deposited some of the aluminum
ions that were dissolved in the soda in your hair. Each day your
hair grows about 1/2 mm, and each day's growth contains trace
amounts of whatever you have eaten. Figure 1 illustrates this.
In 1991, scholars suggested that Zachary Taylor, the 12th
president of the United States, had been assassinated. It was
suggested that because Taylor opposed slavery in new states
seeking admission to the Union, his enemies may have added
arsenic to Taylor's food. If true, the history books claiming
Abraham Lincoln as the first assassinated president would have to
be rewritten. Scientists bombarded samples of Taylor's hair with
neutrons. Any arsenic in his hair would have been changed to a
radioactive form of arsenic known as arsenic-80.
Since arsenic-80 is very radioactive, it is easy to detect
even if present in amounts as little as 0.000 000 000 000 000 01
grams (1 x 10-17 grams). However they did not find arsenic in
Taylor's hair samples, and the arsenic assassination theory
crumpled.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo appearing in General Chemistry by Kask and Rawn,
1993, page 905, Wm. C. Brown Publishers.
WHY DOES RED WINE GO WITH RED MEAT?
Choosing the appropriate wine to go with meals is an enigma
for the majority of diners. However, experts have been offering
a simple rule for generations: serve red wine with red meat, and
serve white wine with fish. Are these cuisine choices mere
traditions, or do more fundamental reasons underlie these
guidelines?
Red wine is usually drunk with red meat because of a
desirable matching of the chemicals found in each. The most
influential ingredient in red meat is fat because the high fat
content gives red meats their desirable flavor. As you chew a
piece of red meat, the lard from the meat coats your tongue and
palate, desensitizing your taste buds. As a result, your second
bite of red meat is less tasty than the first. Your steak would
taste so much better if only you could wash your mouth between
mouthfuls. Fortunately, there is a way to wash away the fat
deposits.
Red wine contains a surfactant that literally cleanses your
mouth, removing fat deposits, re-exposing your taste buds, and
allowing you to savor the next bite of red meat with all the
fervor of the first bite. The chemical in red wine that provides
this soap-like action is tannic acid (also called tannin). Like
sodium stearate (soap), tannic acid consists of both a nonpolar
complex hydrocarbon section as well as a polar one. The polar
part of tannic acid readily dissolves in polar saliva, while the
nonpolar part of tannic acid readily dissolves in the fat film
coating your palate. While sipping red wine, a suspension of
micelles forms in the saliva. This micelle emulsion, with fat
molecules dissolved in its interior, is then easily washed away
upon swallowing.
White wines go poorly with red meats because they lack the
tannic acid needed to purify the palate. In fact, it is the
presence or absence of tannic acid that leaches into fermenting
grapes from grape skins that distinguishes red wines from white
wines. Grapes fermented with their skins are called red wines,
and grapes fermented without their skins are called white wines.
Since fish has far less fat then red meats, fish can be
enjoyed without the additional intake of surfactants. Also,
tannic acid has a rather strong flavor that can overpower the
delicate flavor possessed by many fish. The absence of tannic
acid in white wines gives them a lighter flavor than red wines,
and most people prefer this lighter flavor to accompany their
fish dinners.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo and appearing in General Chemistry by Whitten,
Davis, Peck, and Stanley, eighth edition, 2007, Thomson Brooks
Cole College Publishing.
WHY HOT-WATER PIPES FREEZE BEFORE COLD WATER PIPES
Houses without cellars or basements usually have a crawl space
between the ground and the first floor for servicing plumbing.
People living in houses with crawl spaces may find their water
pipes frozen after a very cold winter night. To their surprise,
it is usually the hot-water pipe that is frozen and not the cold-
water pipe. Cold water pipes freeze before hot water pipes.
Let's see if we can explain why this occurs. Can you dissolve
more gas in hot water or in cold water?
More gas can be dissolved in cold water than in hot water.
Most students answering this question for the first time give the
wrong answers, probably because they know that hot water will
dissolve more solid solutes (like salt and sugar) than cold
water. However, colder solvents dissolve more gas than warmer
solvents. One reason soda pop is refrigerated is to keep it from
losing its carbonation and going flat. Warm soda pop goes flat
faster than cold soda pop.
You've probably observed a related phenomenon when heating
water to the boiling point. Before boiling occurs, many little
gas bubbles you see are dissolved air coming out of solution.
When water is heated in a hot-water heater, the water is
degassed. Dissolved air escapes from cold water as it is heated
in a hot-water heater. Water in a hot-water pipe (supplied by
the hot-water heater) contains less dissolved gas than water in a
cold-water pipe.
Now can you explain why the hot-water pipe freezes before
the cold-water pipe freezes?
The freezing point of water decreases as the concentration
of solute increases. A solute can be a solid, like sugar, or it
can be another liquid, like antifreeze. It can even be a gas,
like air. When air dissolves in water, the freezing point of the
water is lowered. Even though water in a cold-water pipe may
reach the outside temperature faster than water in a hot-water
pipe, the freezing point of the cold water is lower than the
freezing point of the hot water.
There's another factor that must be considered. Just as the
boiling point of a sugar solution increases while the sugar
solution boils, the freezing point of water inside a cold-water
pipe continues to decrease as the freezing process continues. as
water in contact with the sides of the water pipe freezes, gas is
lost from this layer of ice to the unfrozen water in the center
of the pipe. The center water becomes more concentrated with gas
(solute), and its freezing point decreases further. It is
possible to have a pipe with frozen water touching the sides of
the pipe and unfrozen water in the center.
Another factor to consider is that the pressure inside the pipe
increases as water freezes. Why does it increase?
Water expands when it freezes, and the expansion increase
the pressure inside a closed container (such as a pipe). You
have probably observed this if you have ever frozen a liquid in a
closed bottle. The frozen water will either push the top off the
bottle or cause the bottle to crack.
An increase in pressure lowers the freezing point of water.
The freezing point of water in a cold-water pipe is lowered for
two reasons. The freezing point of water decreases when a solute
is added to the water and when pressure is applied to the water.
You will understand why pressure lowers the freezing point of
water after studying Le Chatelier's principle.
Have you ever noticed that the center of an ice cube is the last
part to freeze? Also, there are usually air bubbles in the
center of the ice cube (making the center appear cloudy) while
the outer layer of the ice cube is clear. Can you explain why
these phenomena are observed?
Gases are usually forced from the outer layer of an ice cube
(which freezes first) to the center of the cube. The increase in
the gas concentration in the center of an ice cube keeps the
center unfrozen for a longer period of time. Eventually the
center of portion also freezes and loses its dissolved air, which
appears as a cloudy part of the fully frozen ice cube. Adopted
from an article written by Ronald DeLorenzo appearing in Problem
Solving for General Chemistry, 1993, Wm. C. Brown Publishers.
THE WAR AGAINST THE SUPER GERMS
Not too many years ago, the medical world thought that its
rapidly expanding list of antibiotics would eventually conquer
almost all disease-spreading microbes. However, with the
emergence of certain epidemics, that confidence has disappeared.
Nearly every disease organism known is now resistant to at least
one antibiotic, and many diseases are immune to several
antibiotics. Scourges such as AIDS seem to defy all treatment.
In addition, once-conquered microorganisms such as tuberculosis
bacteria are making a comeback as new antibiotic-resistant
strains called super germs.
Over the last few years, newspapers have been filled with
headlines about super germs. For example, last year, super germs
struck a 1200-student high school in Westminster, California.
One third of the pupils at this high school tested positive for
tuberculosis. Even worse, at least a dozen of the students had
strains of the tuberculosis bacterium that did not respond to any
of the antibiotics administered.
That same year, an epidemic of whooping cough (pertussis)
struck children in Cincinnati. Between 1979 and 1992, there were
542 cases of whooping cough. But in 1993 alone, there were 352
reported cases. Even more alarming was the realization that an
unusually hardy strain of the pertussis bacterium was emerging,
one that was very difficult to treat with standard antibiotics.
In 1994, the cholera epidemic that killed 50,000 in Rwandan
refugee camps involved a strain of the cholera bacterium that
cannot be treated with standard antibiotics.
Also in 1994, one of medicines worst nightmares emerged as a
drug-resistant strain of severe invasive strep A, the so-called
flesh-eating bacteria. Medical doctors are troubled because as
strep A infections increase, these infections will be treated
with antibiotics that will further increase the drug-resistance
of these microbes.
Bacteria become drug-resistant in a variety of ways, one of
which is by producing special chemicals called enzymes. (See the
material on catalysts and enzymes in Chapter 16, Section 16.11.)
Bacteria use enzyme molecules to render inactive drug molecules
such as antibiotics that were once effective in killing the
bacteria. It is the precise way the molecular shapes of enzyme
molecules match antibiotic molecules that allows the enzymes to
trigger the deactivation of antibiotic molecules.
Chemists are trying to fight back by first figuring out the
molecular shapes of the enzyme molecules used by drug-resistant
bacteria. Then chemists may be able to design fighter molecules
with the exact molecular shapes needed to fit precisely onto
enzyme molecules and chemically deactivate them. Once the enzyme
molecules are deactivated by the fighter molecules, the bacteria
are deprived of a crucial element of their defense. The bacteria
become susceptible again to the drugs that were originally
lethal.
Knowing the structure of molecules is critically important
to chemists because knowledge of molecular structures allows
chemists to understand how molecules react. Models such as Lewis
structures and VSEPR theory are vitally important because these
models yield information about molecular structure. Because the
Lewis and VSEPR models are not completely accurate in their
structural representation of molecules, chemists use other more
sophisticated computer models when doing drug research. Computer
software allows chemists to see the structures of molecules on
computer screens before chemists make the chemical in the lab.
By using such models to eliminate chemicals that are unlikely
drug prospects, chemists can reduce the time for developing
disease-fighting drugs by many years.
Were it not for Lewis structure and VSEPR theory models,
both chemistry students and chemists would have to memorize the
individual properties of the many chemicals they encounter.
However, by using VSEPR theory to figure out molecular
structures, students can mimic research chemists by predicting
molecular characteristics such as polarity, hydrogen bonding, and
solubility.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo and appearing in General Chemistry by Whitten,
Davis, and Peck, submitted for their 1996 fifth edition, Saunders
College Publishing.
ENVIRONMENTAL POLLUTION FROM OUTER SPACE
On June 30, 1908, people in China and the Soviet Union saw a
fireball crossing the sky, now popularly known as the Tunguska
meteorite. The fireball landed and exploded in the Tunguska
River Valley in central Siberia. The explosive force, which was
equivalent to that of a 10-megaton nuclear detonation, completely
leveled one thirteen hundred square miles of forest. (In
contrast, Rhode Island is twelve hundred square miles.)
The popular press became interested in the Tunguska
meteorite when investigating teams found no crater. Rumors and
popular press stories attributed the explosion to an alien
spacecraft. A more recent and plausible theory says a comet or
rocky meteorite exploded as it passed through the earth's
atmosphere. It broke up into pieces that were too small to
produce a crater, but its effects were still environmentally
hazardous.
Scientists have determined that the Tunguska meteor
generated enough heat to cause oxygen and nitrogen present in the
atmosphere to react. This reaction formed nitrogen monoxide
(NO). According to their calculations, the meteorite produced
thirty million metric tons of nitrogen monoxide. This nitrogen
monoxide reacted with more oxygen and water to form nitric acid.
From the 30 million metric tons of NO produced by the Tunguska
Meteorite, sixty-three million metric tons of nitric acid formed
in the earth's atmosphere. In comparison, the United States
produces about 25 million metric tons of nitrogen monoxide waste
per year from sources such as automobile exhaust.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo appearing in General Chemistry by Kask and Rawn,
1993, page 108, Wm. C. Brown Publishers.
RAISE THE TITANIC
The Titanic, built in 1912 as an unsinkable luxury ocean
liner, sank on its maiden voyage after colliding with an iceberg.
More than 1500 people died.
Today, the Titanic lies 2 miles beneath the ocean's surface
some 100 miles south of the Great Banks of Newfoundland, Canada.
There is considerable interest in raising the Titanic. Although
there is no major scientific justification for raising the ship,
there will be some commercial value because people are interested
in seeing things of historical significance. However, the
pressure at this depth is about 300 atmospheres (over two tons
per square inch) and too extreme for underwater divers. But some
scientists want the challenge of the advanced technological
problems that such a feat presents. These scientists want to
develop the technology to locate more important objects in the
deep ocean. Scientists also want to expand the technology for
deep-sea photography.
In the past, sunken ships have been raised by attaching
inflatable buoys (big balloons) to them and filling the buoys
with air. Compressors located on surface ships supply the air
needed to inflate the buoys. Unfortunately, commercial pumps are
not available to pump air at pressure of 300-350 atmospheres over
distances of two to three miles.
However there is another way to fill the buoys with gas
other than pumping air into them. You may have seen your science
teacher insert wires from a battery or direct current (D.C.)
generator into a salt solution. While the electricity flowed
through the wires, little bubbles of gas appeared at the end of
the wires. By substituting a D.C. generator for the pump on the
surface ship and a wire for the hose, gas will form at the end of
the wires deep in the ocean. The gas can be used to inflate the
buoy.
Scientists have calculated that it would take a 20-Mw
(20-million-watt) generator operating continuously more than
three years to produce enough gas to raise the Titanic.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo appearing in General Chemistry by Kask and Rawn,
1993, page 658, Wm. C. Brown Publishers.
STRESS-CONTROL AND BIOFEEDBACK CARDS
Many drugstores and health-food stores sell credit card-size
devices known as stress-control or biofeedback cards. Allegedly,
by placing your thumb on a special temperature-sensitive spot
found on these cards, you can determine from the color of the
spot if you are experiencing too much stress. A blue color
(caused by a warm thumb) indicates that you are relaxed while a
black color (caused by a colder thumb) means that you are under a
lot of stress.
The secret behind the special temperature-sensitive spot on
these cards is a chemical known as a liquid crystal. Liquid
crystals substances made up of molecules that hover between being
a solid crystal and a liquid. To understand liquid crystals,
picture a substance made up of long thin charged molecules that
tend to lie next to each other and form layers like pencils in a
box. As you tilt a pencil box, the pencils continue to lie next
to each other up to a point, but if you tilt far enough they roll
over each other. Because such substances share some properties
common to both liquids and crystalline solids, they are called
liquid crystals.
Why does the liquid crystal color depend upon temperature?
Layers of liquid crystal molecules are closely spaced, and
whenever you have closely spaced flat layers, entering white
light is frequently reflected as colored light. You have
probably seen this phenomena when a drop of oil spreads to form a
thin film over a puddle of water. The colors that you see depend
upon the amount of space between the surface of the oil layer and
the top of the water layer below it.
The color that liquid crystals reflect also depends upon the
amount of space between its molecular layers, and the amount of
space between its layers depends upon temperature. At higher
temperatures, liquid crystal molecules vibrate faster which
increases the layer spacing. Since it is this spacing that
determines which colors of light are canceled or reinforced,
liquid crystals change colors as they change temperature.
What does this have to do with stress? Very little.
Although stress makes blood vessels in the hand contract and
cause thumb temperatures to drop, relaxed people in a cool room
will probably have cool thumbs. Also, people who may be under a
high degree of stress or who have just finished a lengthy and
vigorous exercise session will most likely have warm thumbs. So,
although the chemistry behind the stress-control card is
understood, the test results are not as clear cut.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo appearing in Understanding Chemistry, An
Introduction by Dewey, 1994, page 384, West Publishing Company.
THE MIRROR CLOCK WITHIN US
HOW DO YOU TELL A PERSON'S AGE FROM HIS/HER EYES?
Chemists use many techniques to determine the age of
objects. They use carbon dating to find the ages of materials
that were once living. There are limitations with carbon dating,
however. We cannot use it to determine the age of humans or
animals that are still alive. Another limitation is that it is
only very accurate for objects less than about 6,000 years old.
A new method used for dating the age of objects overcomes
some of the shortfalls of carbon dating. Just as your right hand
is a mirror image of your left hand, all living organisms
contain molecules called amino acids that can be left-handed or
right-handed. The right-handed amino acids are mirror images of
the left-handed amino acids. However, for some unknown reason,
the amino acids in all known life forms are left-handed. When an
organism dies or the body doesn't replace amino acid stores, some
of the left-handed amino acids slowly change into right-handed
amino acids. Eventually this change produces an amino acid
mixture that is 50% left-handed and 50% right-handed.
Since we know the speed of this change, we can determine the
age of objects by measuring their left/right amino acid ratio.
Because this technique works for objects up to 500,000 years old,
it addresses one of carbon dating's shortcomings.
Now let's see how this mirror clock (technical name:
stereoisomer clock) works on living people and animals.
Normally, most parts of our bodies produce new amino acids each
day. This production is necessary because our bodies use amino
acids to replace and repair body parts such as skin, hair, and
bones. However, there are two areas of our bodies that do not
produce new amino acids after the moment of birth. The dentin in
our teeth (that's the layer just under the enamel) and our eye
lenses contain the same amino acids today that they did at the
time of birth. Since our bodies do not replace those amino
acids, some of them have been changing into right-handed amino
acids since birth. Therefore it is possible to determine the
ages of living people and animals by analyzing their teeth dentin
or eye lenses. The method is accurate to within 10%.
Using the stereoisomer clock technique, scientists have
verified the ages of former Soviet Georgians who claim to be the
oldest living group of people on earth. Scientists have also
used the method to check the ages of endangered animals to make
better management decisions for aiding animal survival.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo appearing in General Chemistry by Kask and Rawn,
1993, page 829, Wm. C. Brown Publishers.
THE CHEMICALLY CORRECT APPROACH TO STAIN REMOVAL
Have you ever accidentally spilled something on yourself
while rushing to get ready for school or work, and you just don't
have time to change clothes? If you're like most people, you
probably tried to remove the stain by applying a little water
and/or soap to the stained area and rubbing with a washcloth.
Then, to your dismay, when the water dried, you found a circle
(or even worse, a group of concentric circles) surrounding the
area where the stain used to be. You have just unwittingly
practiced some chromatography.
As we saw, chromatography is a separation method that
depends upon differences in the ability of the components of a
mixture to stick or adsorb to surfaces. The stain on your
clothing is probably made up of more than one ingredient, each
with a different ability to cling to clothing fabric. The
ingredients that cling more strongly move a short distance from
the center of the original stain, and the ingredients that cling
less strongly move a farther distance from the center. What was
once one spot may turn into a group of circular stains. If two
ingredients made up the original stain, you would find two
circular stains. If many ingredients made up the original stain,
you would probably find a blur of circles and have difficulty
determining where one stops and another begins.
To avoid this unpleasant outcome, here's the chemically
correct way to remove stains in the future. Place a dry towel or
absorbent cloth on top of the stain and apply water with a damp
wash cloth from the other side as shown in Figure 1. With enough
water, assuming that the stain is water soluble, all of the
components of the stain will leave your clothing and enter the
towel. If the stain is not water soluble, try applying a soapy
solution or using another solvent.
You will probably have to remove the affected piece of
clothing because this approach works better when you apply water
from the side opposite that to which the stain made contact. If
you were to apply water from the same side as where the stain
made contact, you would cause a surface stain to penetrate
further into your clothing and thereby make the stain removal
process more difficult.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo and appearing in General Chemistry by Whitten,
Davis, and Peck, submitted for their 1996 fifth edition, Saunders
College Publishing.
WHY IS EVERYTHING SPINNING?
The universe is rich with spinning entities, including the
gigantic, pinwheel-shaped galaxies comprised of hundreds of
billions of stars and the huge roiling clouds of gas and dust in
interstellar space. These large collections of matter do not sit
quietly and regally in space. They are continuously acted upon
by a multitude of forces: the in-fall of debris from elsewhere,
the pressure of intense radiation, tugs of gravity, the
explosions of dying stars, and even collisions with other
galaxies or gas clouds.
Stars also spin on their axes. Astronomers have measured
the rotation of many stars in our own galaxy and have watched
sunspots move across the face of the sun as it turns. Even
closer to home, you and this newspaper are spinning around with
the earth at about 1000 miles per hour.
The best answer to the question of why everything is
spinning seems to be "Why not?" It's simply more probable.
Picture two moving billiard balls (a useful analogy in science).
If the balls collide, they will probably give each other a
glancing blow. (Think about the one chance for a perfect head-on
collision compared with the many chances for lesser collisions at
all other angles.) Glancing collisions make both balls spin, and
glancing collisions throughout the universe keep everything else
spinning as well.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo appearing in Understanding Chemistry, An
Introduction by Dewey, 1994, page 138, West Publishing Company.
BEER/SODA CAN OPENING: A PROPER METHOD
If you've ever shaken a can of soda before opening it with a can
opener or popping the flip top, you know the mess that can occur
when the soda sprays from the can. Some of the more experienced
soda drinkers know of a technique that eliminates the mess: Tap
the sides of the soda can before opening it. Tapping the sides
prevents the soda from spraying out. Let's see what Boyle's law
has to do with this.
When you shake a can of soda, the tiny gas bubbles created
by the shaking adhere to the sides and the bottom of the can.
What happens to the tiny gas bubbles adhering to the sides of the
can when the can is opened? (Hint: Soda cans are sealed under
pressure.)
When a can of soda is opened, the pressure inside the can is
reduced. The pressure reduction causes the gas bubbles adhering
to the inside wall to expand, pushing out the soda and making the
aforementioned mess.
How does tapping the sides of the soda can eliminate this mess?
Tapping the sides of the soda can causes the tiny gas
bubbles to rise to the top of the can where their expansion (when
the can is opened) is noticed only by a rush of gas from the can
(as opposed to a rush of soda).
Buy a six-pack this weekend and perform this experiment
yourself. Adopted from an article written by Ronald DeLorenzo
appearing in Problem Solving for General Chemistry, 1993, Wm. C.
Brown Publishers.
SINKHOLES
In our attempt to clean up environmental air pollution, we
may have unleashed an unexpected environmental phenomenon called
sinkholes. Sinkholes are openings in the ground that form from a
sudden sinking of the soil. In a matter of seconds, a monstrous
sinkhole 400 feet across and 125 feet deep formed in Shelby
County, Alabama. It was the largest of more than 1,000 sinkholes
that have formed in Shelby County over a fifteen-year period and
one of an estimated 4000 collapses that have occurred throughout
Alabama. Some of these Alabama sinkholes have occurred beneath
major highways and railroad tracks, and some have drained lakes
so quickly that live fish were left wriggling on dry land. In a
suburb of Orlando, Florida, a giant, two-and-a-half acre sinkhole
produced a crater that swallowed homes, yards, parking lots, a
city owned swimming pool, a foreign-car repair shop, and portions
of two streets.
Sinkholes tend to form in areas where the ground rests on a
bedrock of limestone, above which lie thick clay and sand
deposits. Over periods of hundreds of thousands of years,
rainwater produces cracks and caverns in the limestone. However,
as long as underground caverns hold water, the ground isn't
likely to collapse because the water produces a buoyant support.
Subsurface clay is partly held up by the cavern walls and partly
by the water. As deep wells from the surface pump water from the
limestone caves, the support from the water vanishes. Then,
sometimes only the weight of a passing animal or the distant
rumble of a train can trigger the collapse of one of these
cavities, leaving a hole in the earth's surface.
Some think that the solution to preventing sinkholes is
simply to cut down on the use of ground water, and that water
must not be drawn out faster than the rains and runoffs can
replenish it. But others point out that there are many areas in
the U.S. that are honeycombed with caverns and where the ground-
water level has been lowered, yet several of these areas do not
have sinkholes. This latter observation has led chemists to
think that there are other factors such as air pollution that
contribute to the formation of sinkholes. Here's how air
pollution can produce sinkholes.
Some air pollutants make rain acidic. For instance, burning
sulfur-containing oil and coals produces sulfur dioxide (SO2).
Sulfur dioxide dissolved in rainwater turns the rainwater into a
sulfuric acid (H2SO4) solution. When this acidic rain seeps into
limestone formations, the sulfuric acid reacts with the calcium
carbonate in the rock and dissolves the rock. As the rock
dissolves, cavern walls crumble, and the ground collapses.
However the problem may be more complex than that because,
over the years, there has been a decrease in the sulfur content
of coal and oil, yet the acidity of rain water has continued to
increase and the incidence of sink holes has also increased. If
sinkholes form because of the acid rain produced by air
pollution, why are the number of sinkholes increasing and why is
the acidity of acid rain also increasing? Some believe the
answer to this question is linked to our efforts since the 1930s
to rid the atmosphere of soot pollution.
During the 1930s, Americans were proud of the soot-producing
smokestacks dotting the country because the smokestacks and soot
symbolized our power and progress as an industrialized country.
Because soot particles are so small in size, they may actually
have been beneficial. (Particles the size of soot are called
colloidal particles. See the subsection on colloids in Chapter
14, section 14.15). An important property of many solids is that
as the solid is divided into smaller and smaller particles, the
overall surface area of the original solid increases. (See also
Chapter 14, section 14.17, "The Adsorption Phenomenon"). In
fact, if a cube the size of an M&M is divided in half one
trillion times, its surface area increases to about 1.5 acres.
This increased surface area is important because the larger the
exposed surface of a solid, the more material that can adhere to
its surface. So one theory to explain the discrepancy between
decreased sulfur content and increased sinkhole production is
that the large surface area of the soot attracted much of the
sulfur dioxide molecules from the air. But there may be another
important consideration. Soot normally contains impurities such
as iron oxide (Fe2O3) that can neutralize SO2 just as bases can
neutralize acids. Here's how this neutralization takes place
between the iron oxide and the sulfur dioxide.
Metal oxides such as iron oxide (Fe2O3) can react chemically
as bases while nonmetal oxides such as sulfur dioxide cam react
chemically as acids. Some chemists believe that the large
surface area of soot allowed its iron oxide contents to react
with the sulfur dioxide in the air in the following acid-base
neutralization reaction:
3 SO2 + Fe2O3 ----> Fe2(SO3)3
If such a reaction played a significant role in removing
sulfur dioxide pollution from the atmosphere in the 1930s, then
our attempts since then to rid the atmosphere of soot may have
had unforeseen consequences. In removing soot we may have
inadvertently increased the sulfur dioxide concentration in the
atmosphere which in turn may have contributed to the current
epidemic of sinkholes.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo and appearing in General Chemistry by Whitten,
Davis, and Peck, submitted for their 1996 fifth edition, Saunders
College Publishing.
NUCLEAR RADIATION AND CAR TIRES
When nuclear radiation strikes atoms and molecules, the
radiation can make those atoms and molecules become charged. It
is precisely this ability charge matter that makes the use of
radioactive substances economically valuable in a wide range of
applications. Few people are aware that the economic impact of
these uses is billions of dollars. For example, ionizing nuclear
radiation is used to sterilize hospital clothing and equipment
such as syringes and to sterilize food to preserve it. It is
even used to enhance the properties of natural rubber which is
then used in the manufacturing of your automobile tires, and it
is a cleaner method than the alternative.
Despite people's fascination with rubber, for a long time
one major problem kept rubber from becoming more widely used: its
physical properties changed dramatically with temperature. At
warmer temperatures rubber became gooey and sticky, and at colder
temperatures rubber became hard and brittle--until 1840 when
Charles Goodyear had his lucky accident. He spilled sulfur and
rubber onto a hot stove. The resulting chemical reaction ruined
his indoor air quality, but it improved the rubber, making it
less temperature sensitive.
The process of heating a mixture of rubber, sulfur, and
various toxic chemicals is called vulcanization, and for decades
following Goodyear's discovery, rubber was vulcanized to improve
its properties. Today, natural rubber is frequently treated with
radiation to achieve the same results--without using toxic
chemicals.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo appearing in Understanding Chemistry, An
Introduction by Dewey, 1994, page 531, West Publishing Company.
THE REAL REASONS ROCKS CRACK
Because of our experiences finding shattered frozen jars of
food and cracked frozen water pipes, most of us incorrectly
hypothesize that rocks also crack in a similar manner when
subjected to sub-freezing temperatures. We believe that water,
which has soaked into the rocks, freezes, expands, and cracks the
rocks. Although water which has soaked into rocks does expand
when it freezes (in fact it begins to expand as it cools below
4o C), freezing water isn't responsible for cracking rocks. To
better understand why rocks really crack, let's first examine how
the polarity of water molecules causes the volume of a bulk water
sample to expand when cooled below 4o C.
Water molecules are polar, a fact that can be easily
demonstrated with a rubber rod and piece of cats fur. Rubbing
the end of a rubber rod with cats fur produces a negative static
electric charge on the rubber rod. When the negatively charged
end of the rubber rod is positioned close to water slowly flowing
from a faucet, the water stream is deflected towards the
negatively charged rod. At first you might guess that water
molecules are positively charged since opposite electrical
charges attract one another. However, when the experiment is
repeated with a glass rod whose end has been rubbed with a silk
cloth, thereby producing a positive static electrical charge on
the glass rod, a stream of slowly flowing water is also deflected
toward the positively charged glass rod.
At first there seems to be a paradox. How can water be
attracted to both positively and negatively charged rods? Can
water molecules act as if they are positively charged one instant
and negatively charged the next? Scientists use the polarity of
water molecules to answer these questions. Since water molecules
are polar and free to rotate, when water molecules flow by a
positively charged glass rod, the molecules rotate to orientate
their negative ends facing the rod and their positive ends facing
away from the rod. When the same stream of water flows by a
negatively charged rubber rod, the water molecules once again
rotate to orientate their positive ends facing the negatively
charged rod and their negative ends facing away from the rod.
It is this polarity and ability of water molecules to rotate
that makes bulk samples of water expand when temperatures fall
below 4o C. When water is cooled, the water molecules move more
slowly, and the electrostatic attractions and repulsions between
the positive and negative ends of the water molecules become more
pronounced. Most forces such as gravitational, magnetic, sexual,
as well as electrostatic become more effective between two
objects as the speed of the objects decreases. When water is
cooled to 4o C, the polar water molecules begin to line up due to
the interactive electrostatic forces between the water molecules
that become more effective at colder temperatures (lower speeds).
This alignment of the polar water molecules forms a structure
that causes the water to occupy more space, and, as water expands
with further cooling, it begins to press against the walls of its
container.
Several years ago, scientists decided to determine if
freezing water was really responsible for rocks cracking. The
scientists studied nineteen specimens of frost sensitive rocks,
most of which were dolomite (a magnesia-rich sedimentary rock
resembling limestone and made up of magnesium and calcium
carbonate) and limestone (a shaly or sandy sedimentary rock
composed chiefly of calcium carbonate). Such rocks usually
contain countless pores into which water can easily enter. First
the scientists soaked these rock samples in water, then
repeatedly warmed and cooled the water-laden rocks while always
keeping the temperature at or above room temperature (about
20o C). Even though the temperature never came close to the
freezing point of water (0o C), or even close to the temperature
at which water begins to expand (4o C), all of the rocks cracked.
Although something other than freezing was cracking these rocks,
this experiment did not rule out the possibility that freezing
water is also responsible for rocks cracking. To test the effect
frozen water on the rocks, the scientists then subjected the
rocks to sub-freezing temperatures.
Even when the rocks were cooled to -40o C, none of the water
froze in eight of the samples, and less than half of the water
froze in the remaining samples. Why was this so? Remember that
water enters the interior of these rocks through very small
pores. As a result, water seeping into these pores exists in
thin films. Scientists know that thin films or microscopic
amounts of matter frequently have different physical properties
than bulk amounts. For example, minute water droplets in clouds
frequently don't freeze until the surrounding temperature falls
below -40o C.
If freezing water doesn't crack these rocks and if the rocks
crack at room temperature, what did cause the experimental rocks
to crack? The scientists suspected that the cracking had
something to do with the polar nature of water molecules. To
test this possibility, they next soaked the test rocks in
nonpolar solvents. After these rocks soaked in nonpolar
solvents, they were repeatedly warmed and cooled back to room
temperature. After several such cycles, none of them cracked.
What is it about polar solvents that cause frost-sensitive
rocks to crack? The pores of frost-sensitive rocks are lined
with thin layers of electrically charged clay. At room
temperature, the polar water molecules line up so that their
charged ends get closer to the opposite charges on the clay
surfaces. This alignment forms a structure that occupies more
space, and this in turn exerts a force that is powerful enough to
crack the rocks. When the rocks are warmed, this alignment is
destroyed by the increased kinetic energy of the water molecules.
As the cycles of warming and cooling continue, these cycles cause
the thin water film to repeatedly exert and release a pressure
within the rocks that eventually causes the rocks to crack.
Because water rarely freezes within rock pores, rocks do not
crack because of the stress exerted by freezing water. It is the
repeated pressure exerted by the thin layer of water when its
volume begins to increase around 20o C that cracks rocks, and
this unusual volume increase at such a relatively high
temperature takes place because of the attraction between the
polar water molecules and the charged clay within the pores of
frost-sensitive rocks.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo and appearing in General Chemistry by Whitten,
Davis, and Peck, submitted for their 1996 fifth edition, Saunders
College Publishing.
SURVIVE DROWNING WITHOUT BRAIN DAMAGE
For decades the medical community believed that anyone who
stays underwater for more than three minutes risks permanent
brain damage. The brain, they believed, could not survive more
than three minutes without oxygen. Also, they said that death
was very likely after six minutes without oxygen.
In 1975, a Michigan teenager drove his car into an icy pond
and remained under water for about 38 minutes. When rescuers
found him, medical authorities officially pronounced him dead.
His heart and breathing had stopped. However, when rescuers gave
him CPR, he regained consciousness and went on to live a normal
life.
There are dozens of amazing examples of humans surviving
under fatal conditions. One recent survivor was a 3-year old
girl in West Virginia. Wearing only a nightgown, she had spent
about five hours in 27-degree weather before friends found her
lying in the snow. Because she had no heartbeat and her
breathing had stopped, she was clinically dead. But as with the
Michigan youth, resuscitation efforts paid off, the girl was
revived and suffered no brain damage.
Brain damage does occur when we deprive ourselves of oxygen
for more than three minutes under normal circumstances. The key
words are "normal circumstances," and this assumes normal body
temperatures persist during oxygen deprivation. In each of the
dozens of documented cases where victims emerged unharmed from
life-threatening situations, the victims tended to be children
and the accidents took place in very cold environments. One
reason for these miraculous survivals is that the speed of
chemical reactions (including those involved with life processes)
decreases with decreasing temperature. When our bodies are
cooled, the chemical reactions that keep us alive slow down, and
this reduces our need for oxygen.
It's interesting to understand why most of these dramatic
rescues happened with children. Children's smaller bodies cool
down much more quickly than adult bodies. By the time most
larger adult bodies cool down to benefit from a decreased oxygen
need, they have already been irreversibly damaged from lack of
oxygen.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo appearing in General Chemistry by Kask and Rawn,
1993, page 791, Wm. C. Brown Publishers.
RADON AND TOBACCO SMOKE: A DEADLY COMBINATION?
It's no secret that lung cancer kills--over 120,000
Americans die from the disease each year. The leading cause of
lung cancer is well-publicized; the United States Surgeon General
has been warning us about the dangers of tobacco smoke for many
years. The second leading cause is radon, a naturally occurring
radioactive gas. Because of its widespread presence, the Federal
government urges Americans to test their homes for radon, which
may seep into foundations from surrounding soil.
What most people don't know is that radon and tobacco smoke
form a deadly combination--far deadlier than either is
separately. In fact, tobacco smoke can make radon gas more
deadly by a factor of up to 1500%. Let's examine why.
Radon itself is relatively harmless. If you inhale a radon
atom, you will probably exhale that radon atom with no problems.
The danger arises when radon, a gas, decays to produce
radioactive particles--most importantly, polonium. If this
should happen while the radon atom is in your lungs, your risk of
lung cancer increases. Fortunately, the chance of this happening
is small--unless there is tobacco smoke present. Tobacco smoke
greatly increases your chances of inhaling dangerous radioactive
polonium. That's because tobacco smoke has the ability to absorb
polonium particles and keep them in the air for many hours or
even days.
The hazards of radon in combination with tobacco smoke
affect everyone present, not just the person who lights up. Not
only that, but the potential danger persists well after the
cigarette has been snuffed. The risk of cancer posed by this
deadly pair is well worth considering for smokers and non-smokers
alike.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo appearing in Understanding Chemistry, An
Introduction by Dewey, 1994, page 423, West Publishing Company.
CAN PRESSURE COOKERS SAVE THE ENVIRONMENT?
Vice-president Al Gore may have articulated it best when he
said, "Nothing links us more powerfully to the Earth--to its
rivers and soils and its seasons of plenty--than food. It is a
daily reminder of our connection to the miracle of life." How
fitting it is that our kitchens provide us with both this daily
remembrance and some solutions to our basic ecological and
environmental problems.
Many of us are aware of the health benefits of a low-fat
diet and the wholesome pleasures of eating grains and fresh
vegetables. However, preparing such meals from scratch has
always been a time-consuming enterprise. Because of the time
needed, providing these meals appears a difficult or impossible
goal for many overly-busy, two-wage-earner households. Enter the
pressure cooker that can cook foods more quickly. Foods cook
more quickly in a pressure cooker because its high pressure makes
water boil at higher temperatures. The higher temperature of the
boiling water allows the pressure cooker to produce full-flavored
vegetarian dishes such as lentil soups and perfect brown rice in
a matter of minutes.
Consuming more vegetarian dishes favorably affects more than
just our taste buds. Many ecologists and environmentalists
believe that the more fruit, vegetables, and grains we consume in
our daily diets, the more we can improve the environment and
conserve the earth's vital resources. This environmental
improvement and resource conservation takes place because plant-
based diets lessen the waste of grain and the devastation of
land, water, and human resources that result from large-scale
rearing of animals domesticated for their meat.
Fortunately for us, this low-fat diet that is being
advocated for the well-being of the planet is the same low-fat
diet that health experts currently advocate for maximum human
fitness. Such diets are beneficial to human health because
grains, beans, fruits, and vegetables are high in fiber and
totally free of cholesterol.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo and appearing in General Chemistry by Whitten,
Davis, and Peck, submitted for their 1996 fifth edition, Saunders
College Publishing.
WHAT'S THE DIFFERENCE BETWEEN AN ARTIFICIAL ICE SKATING RINK
AND PLASTIC FOOD WRAP?
The petroleum we get from oil wells is made up of a mixture
of molecules called hydrocarbons. Hydrocarbons are molecules
that contain only atoms of hydrogen and carbon. There is a
relationship between the number of carbon atoms in a hydrocarbon
and its physical properties such as how easily it flows
(viscosity) and how easily it evaporates (volatility). For
example, hydrocarbons with between one and four carbon atoms per
molecule (methane, ethane, propane, and butane) are gases.
Gasoline, a volatile liquid, is a mixture of hydrocarbon
molecules containing from six to twelve carbon atoms. Kerosene,
less volatile than gasoline, is another mixture of hydrocarbons
containing nine to fourteen carbon atoms per molecule. Because
of its decreased volatility, kerosene is a safer fuel than
gasoline in room heaters.
As the number of carbon atoms per hydrocarbon molecule
increases, we progress from kerosene to fuel oil to lubricating
oils. Each mixture in this progression becomes more viscous and
less volatile. Eventually, as we continue to increase the number
of carbon atoms, we obtain grease, asphalt, and tar.
Chemists can join small molecules together to make larger
molecules called polymers. For example, small molecules of
ethylene can be joined together to become larger molecules called
polyethylene. As the size of the polyethylene molecule
increases, so does its viscosity. When chemists polymerize
ethylene to produce molecules with about 40,000 carbon atoms, the
result is material we use in plastic food wrap. If we increase
the number of carbon atoms per polyethylene molecule even
further, we produce even tougher products. One of these is
suitable for use in flexible milk bottles (60,000 carbon
atoms/molecule), and another in more rigid bleach bottles (80,000
carbon atoms/molecule).
When the number of carbon atoms per polyethylene molecule
reaches 800,000, the material becomes very viscous and abrasion
resistant. Such material can be used as a substitute for metal
bearings and as artificial ice in skating rinks.
The polyethylene surface used in artificial ice skating
rinks is 60% less expensive to maintain than real ice. After
four years of daily vacuuming and weekly silicone treatments,
maintenance workers flip the rink over to expose the unused
bottom surface. This fresh surface is good for another four
years.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo appearing in General Chemistry by Kask and Rawn,
1993, page 863, Wm. C. Brown Publishers.
THE OSMOTIC PILL
When we repeatedly take medication over prolonged periods,
the drug concentration in our bodies varies. The drug
concentration is higher than necessary shortly after taking a
pill, and its concentration falls below effective levels just
before we take the next pill. When drug concentrations are too
high, the risk of developing side effects increases. When drug
concentrations are too low, the disease may gain ground.
Time-release pills do not correct this problem; they merely
reduce the number of times per day that we swallow pills. As
time-release pills release a dose of medication, the same pattern
of excessive and inadequate drug concentrations occurs.
An exciting area of drug research today is the development
of an effective osmotic pill. Remember that osmosis is the
process that takes place when raisins are placed in a glass of
tap water and left overnight (see The Macon Telegraph, November
2, 1993, page 5-D). Because the salt and sugar concentrations
inside the raisins is higher than that in the tap water, the
raisins draw in water and blow up like miniature balloons. The
osmotic pill would look like that shown below.
We begin by filling the first chamber with a saturated
solution of a salt. We want to make the concentration of the
salt inside the first chamber higher than that found in the body.
Then water from body fluids will pass through the semipermeable
membrane (just as water passes through the raisin skin into the
raisin). This exerts pressure on the elastic impermeable
membrane that in turn pushes the drug through a small laser-
drilled hole provided at the other end. This assures a constant
dose delivery and a constant drug concentration within the body.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo appearing in General Chemistry by Kask and Rawn,
1993, page 601, Wm. C. Brown Publishers.
OPERATION DESERT HELL
To many it was the Blaze of the Century. Temperatures were
so high that even the sand melted into glass while dazzling
orange flames billowed 60 feet into the air. The firefighters
who battled the 1500 degree F heat had another name for this
Kuwaiti war aftermath. They called it Operation Desert Hell.
The saga began when Iraqi President Saddam Hussein sent his
military forces to invade Kuwait in 1990. After the United
States intervened, retreating Iraqi soldiers set fire to over 600
oil wells. Kuwaiti officials estimated that about six million
barrels of oil a day went up in smoke, at a cost of over $1,000 a
second. Air pollution from the fires was a serious environmental
concern, with smoke plumes reaching countries over 1,200 miles
away from Kuwait. Firefighters from around the world converged
on Kuwait to help extinguish the burning oil wells and to
minimize the resulting environmental damage.
Frequently, oil fires are snuffed out by exploding dynamite
above burning wells, depriving the fires of oxygen needed to
support combustion. Using dynamite to extinguish oil well fires
requires large reservoirs of water for two important reasons.
First, water is needed to keep the explosives cool until they are
detonated. Secondly, since the explosives can extinguish an oil
fire only briefly, additional water is needed to prevent hot
structural metal from reigniting the blaze.
When large reservoirs of water are unavailable, oil-well
firefighters' turn to nitrogen to help put out the blazes because
using nitrogen requires only a few thousand gallons of water.
Before nitrogen can be used, firefighters attach a 25-foot steel
tube with a 2.5 foot diameter to a long pole extending from a
crane. Workers then connect one end of a hose to the base of the
25-foot steel tube and the other end of the hose to a nearby
truck containing liquid nitrogen. Burners are used to warm the
liquid nitrogen thereby changing it into a gas before it reaches
the steel tube. The crane places the steel tube over the spout
of burning oil forcing the well to propel its burning oil through
the tube and out of the top. The burning oil gushing from the
top of the steel tube resembles an enormous Bunsen burner. At
this stage, the sound intensity softens from that of a jet engine
to one of a passing train. Now nitrogen gas is pumped into the
base of the steel tube. Since nitrogen does not support
combustion, the fire is quickly smothered as nitrogen displaces
oxygen from the fire's base.
In addition to nitrogen's inability to support combustion,
nitrogen has another important property that makes it
particularly useful to fight oil well fires. As we just saw in
this section, molecular orbital theory predicts that nitrogen
molecules have a bond order of three, the maximum bond order
possible for a diatomic molecule. The greater the bond order of
a diatomic molecule, the more stable we expect the molecule to
be. Because of nitrogen's stability, nitrogen can withstand the
intense heat produced by the burning oil.
While nitrogen gas is pumped into the base of the steel
tube, water is used to cool the tube to prevent it from melting.
After about a minute, the flames shooting from the top of the
steel tube are extinguished, and in their place emerges a fifty-
foot fountain of hot but non-burning oil. The dangerous part has
just begun because hot oil from the oil fountain rains down
covering machinery and workers alike, and the slightest spark
could ignite the oil again. To protect the firefighters from a
re-ignition, water canons continuously shoot steams of water at
the firefighters until they complete their work and shut off the
oil flow.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo and appearing in General Chemistry by Whitten,
Davis, and Peck, submitted for their 1996 fifth edition, Saunders
College Publishing.
THE EXTENSIVE USE OF NUCLEAR RADIATION IN OUR DAILY LIVES
We saw earlier in this chapter that emissions from
radioactive samples have enough energy to ionize gas molecules in
Geiger-MÅller counters. Because of this ability to ionize
matter, energy emitted by radioactive materials is called
ionizing radiation. It is precisely this ability that makes
these emissions economically valuable in a wide range of areas.
Few people are aware of the vast impact of ionizing nuclear
particles upon our daily lives. The use of nuclear particles is
a multi-billion dollar per year industry with a healthy growth
rate. However, most of this influence is a well-kept secret
because many in the industry believe Americans fear anything
concerning nuclear radiation. As a result, items such as food
treated with radiation are marked with the innocuous word
"picowaved" accompanied by the emblem of an outlined flower. In
the medical profession, the term "Nuclear Magnetic Resonance" was
replaced by "Magnetic Resonance Imaging" or "MRI" for similar
reasons.
Let's begin exploring the influence of nuclear chemistry by
considering the economic impact of ionizing radiation on the U.S.
poultry market. For years, the United States has been at a
disadvantage trying to export its chickens and turkeys to eastern
European countries and to the former Soviet Union. Imported
poultry must be kept refrigerated as it travels overseas.
Because refrigeration costs are so high, Europeans and Asians
must pay more for our poultry than they would pay for poultry
from closer sources.
Fortunately, refrigeration is only one of several ways to
keep food from spoiling, and irradiating food is an alternative
that is considerably less expensive than refrigeration. Gamma
radiation passing through food ionizes bacteria and other food-
destroying organisms present in the food. The irradiated food is
essentially sterile, and this sterility lessens its need for
refrigeration or freezing. In fact, if enough radiation is
administered, food can be kept for long periods in sterilized
containers without any refrigeration. In 1992, the Agriculture
Department allowed poultry processors to use ionizing radiation
to preserve some five billion chickens and turkeys that await
slaughter each year in the United States.
The world of art has also felt the influence of nuclear
chemistry. Fine art such as paintings decay for the same reason
as food: microorganisms eat away at the canvas and wood.
Ionizing radiation is used to preserve works of art, and the
radiation accomplishes this by killing the offending organisms.
The art world also benefits from archaeometry, a branch of
science dedicated to the service of the arts. Archaeometry
combines the talents of chemists and other scientists for both
restoring and authenticating valuable works of art. Recently,
these scientists turned their attention to The Man With the
Golden Helmet, a well-known and widely distributed painting.
When archaeometrists treated the original painting with nuclear
particles, the results were different from the results obtained
from other authenticated Rembrandt's paintings. Overnight the
price of this masterpiece fell from eight million dollars to a
few hundred thousand dollars.
Not only do nuclear particles kill the organisms that spoil
food and rot art treasures, radiation is also used to sterilize
hospital supplies and operating room equipment. In a similar
use, nuclear particles clean up the environment by decomposing
industrial wastes and obliterating sewage pathogens. Other
applications include treating cancer patients, diagnosing heart
and brain disorders, curing paints, and altering the properties
of rubber.
From identifying and preserving works of art to eliminating
economic handicaps for U.S. poultry producers, and from improving
the quality of our automobile tires to curing once incurable
diseases, nuclear chemistry has made a major influence on most of
our lives.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo and appearing in General Chemistry by Whitten,
Davis, and Peck, submitted for their 1996 fifth edition, Saunders
College Publishing.
CHEMICALS IN THE EVERYDAY WORLD:
WHY BARNS AND SUPERMARKET MEATS ARE RED
You may have encountered many simple yet interesting
chemical compounds for years without being weren't aware of them.
For example, did you know that barns are red today because
historically they were once preserved with rust [Fe2O3]? In the
mid-1800s, American farmers made an inexpensive yet long-lasting
barn preservative by mixing reddish (actually rust colored)
iron(III) oxide, skim milk, linseed oil, and lime (CaO, calcium
oxide). By the late 1800s, red had become the traditional color
for barns. Barns aren't still red because of rust--they are red
because of red paint pigments. But historically, they are red
because of rust.
Another use of chemicals in everyday life can be found in
the supermarket. What keeps meat at the supermarket looking
fresh? The color, flavor, and texture of meats depend on
additives such as sodium nitrite (NaNO2) and sodium nitrate
(NaNO3). Sodium nitrate also acts as a preservative, and its use
has virtually wiped out botulism food poisoning. Despite this,
the Food and Drug Administrations has been trying to limit the
concentration of these two chemicals because excessive amounts
may be harmful. Food processors add iron(II) sulfate (FeSO4) and
iron(III) phosphate (FePO4) to many breads and cereals as a
dietary source of iron.
You probably think that the only chemical in table salt is
sodium chloride. But there are 20 other chemicals in each
serving of salt. Sodium chloride is the primary ingredient, but
table salt contains many additives. One of these, KI (potassium
iodide), is a nutrient. Sodium hydrogen carbonate (NaHCO3),
sodium carbonate (Na2CO3), calcium hydroxide [Ca(OH)2], and
disodium hydrogen phosphate (Na2HPO4) are also present to help
stabilize the potassium iodide. Magnesium carbonate (MgCO3),
calcium hydrogen phosphate (CaHPO4), calcium phosphate Ca3(PO4)2,
and calcium carbonate (CaCO3) are present as desiccants (drying
agents) to help keep the salt crystals from fusing.
Some other chemicals that you may find around your own home
include SiO2 (silicon dioxide, sand), NaOH (sodium hydroxide,
lye, used in drain cleaners), and H2SO4 (sulfuric acid, battery
acid). Also found are CuSO4 (copper(II) sulfate), an algicide,
HCl (hydrochloric acid, called muriatic acid, used to clean
masonry and bricks), and NaClO (sodium hypochlorite, used in
liquid laundry bleach).
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo and appearing in General Chemistry by Whitten,
Davis, Peck, and Stanley, eighth edition, 2007, Thomson Brooks
Cole College Publishing.
PREPARING FOR HIGH ALTITUDE OLYMPIC GAMES
High altitudes decrease athletic performance because oxygen
concentrations in air decrease as elevation increases. The
oxygen concentration at sea level is 21%, but it decreases to 17%
at 5000 feet. Given enough time, most people can easily become
acclimated to lower oxygen concentrations. As a general rule,
people need about four hours a day for one week to acclimate for
every 3000 feet of elevation.
Athletes who train at low elevations but then compete at
higher elevations may be at a disadvantage compared with athletes
who both train and compete at higher elevations. When high-
altitude cities host Olympic Games, contenders who are native to
geographical areas with lower elevations have various options.
Some have moved to the cities hosting the Olympic games several
weeks or months in advance and practice under competition
conditions. Other athletes have injected themselves with their
own red blood cells just before competitive events. The
injection increases the oxygen-carrying efficiency of their
blood, and the increased efficiency improves athletic
performance. Although this technique is otherwise legal, it is
banned in Olympic competition.
Another option involves the use of a device called an Oxygen
Partial Pressure Exerciser. The purpose of the Exerciser is to
mimic the atmospheric conditions of higher altitudes. It
consists of a face mask and one or more canisters worn in a back
pack. The exerciser mixes fresh air and recycled exhaled air so
it can deliver air with any preset oxygen concentration, thereby
mimicking the atmospheric compositions at various altitudes.
Since we exhale carbon dioxide, you might guess that this
device doesn't really mirror high altitude breathing because the
device delivers air that has a higher-than-normal carbon dioxide
concentration. However, the Oxygen Partial Pressure Exerciser is
designed to reduce the excessive carbon dioxide concentration.
To accomplish this carbon dioxide concentration reduction, one
canister allows some exhaled air to pass through a solution of
barium hydroxide. Barium hydroxide removes carbon dioxide by a
neutralization reaction to produce insoluble barium carbonate.
CO2 + Ba(OH)2 ----> BaCO3 + H2O
As a result, users of the Oxygen Partial Pressure Exerciser
inhale air that has both the desired lower oxygen concentration
and a normal carbon dioxide concentration.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo and appearing in General Chemistry by Whitten,
Davis, and Peck, submitted for their 1996 fifth edition, Saunders
College Publishing.
DINOSAUR EXTINCTION THEORIES
Scientists can use neutrons to determine which chemical
elements are present in unknown samples and how much of each
element is present. When bombarded with neutrons, elements in
the treated sample absorb some of the neutrons and turn into
radioactive isotopes. Each radioactive isotope emits its own
characteristic radiation, and by making careful measurements to
determine the type of radiation being emitted, scientists can
determine which isotopes are present (qualitative analysis).
Since the intensity of radiation depends only on the amount of
radioactive material present, it is also possible to determine
how much of each radioactive element is present in the unknown
sample (quantitative analysis). Neutron bombardment has been
used to deduce the demise of dinosaurs.
You may have read the theory that dinosaurs became extinct
after a very large comet struck the earth 65 million years ago.
The comet broke into two pieces that landed in Iowa and the
Yucatan Peninsula. Dust from the impacts circled the globe and
blocked out the sun for several years. During that time
photosynthesis stopped, land and marine plants died, and most
animal life vanished. Eventually the dust, very rich in the
element iridium, settled evenly on the earth's surface. How did
scientists develop this interesting explanation?
Scientists used neutrons to bombard the Cretaceous Layer, a
sedimentary rock layer that deposited 65 million years ago about
the time of the dinosaur extinction. The bombarding neutrons
reacted with iridium in the 65-million year old rock layers as
follows.
193Ir + n ----> 194Ir
Iridium-193 is not radioactive, but iridium-194 is so radioactive
that billionths of a gram per cm3 of soil can easily be detected.
After bombarding the Cretaceous Layer, its radioactivity from
decaying 194Ir atoms was 1.89 x 109 disintegrations per second
per cm3 of soil. The activity of other sedimentary layers
bombarded with neutrons, both older and younger than the
Cretaceous Layer, was 7.87 x 107 disintegrations per second per
cm3 of soil.
Using the equation
Rate of decay = kN
and knowing the half-life of iridium-194 (19 hours), we can
calculate the concentration of iridium atoms in grams per cubic
centimeter of soil. Performing these calculations for soil that
is younger or older than the Cretaceous Layer,
Rate = kN = (0.693/t1/2)N
7.87 x 107 194Ir atoms/sec/cm3 =
[(0.693)(N)]/[(19 hr)(3600 sec/hr)]
Solving for N,
N = 7.77 x 1012 194Ir atoms/cm3
Next, the mass of iridium-194 present per cubic centimeter of
soil is determined.
[7.77 x 1012 194Ir atoms/cm3] x
[194 g 194Ir/6.02 x 1023 194Ir atoms] =
2.5 x 10-9 g 194Ir/cm3
Likewise, we can find the concentration of iridium-194 atoms in
the Cretaceous layer.
Rate = kN = (0.693/t1/2)N
1.89 x 109 194Ir atoms/sec/cm3 =
[(0.693)(N)]/[(19 hr)(3600 sec/hr)]
Solving for N,
N = 1.86 x 1014 194Ir atoms/cm3
Next, the mass of iridium-194 present per cubic centimeter of
soil is determined.
[1.86 x 1014 194Ir atoms/cm3] x
[194 g 194Ir/6.02 x 1023 194Ir atoms] =
6.0 x 10-8 g 194Ir/cm3
Calculating the percent increase of iridium in the Cretaceous
Layer,
[(6.0x10-8 g/cm3 - 2.5x10-9 g/cm3)/(2.5x10-9 g/cm3)] x 100%
= 2300% increase in 194Ir concentration
These calculations show that 65 million years ago, there was
a 2300% increase in the concentration of iridium in the Earth's
crust. Since most terrestrial iridium found has extraterrestrial
origins, the giant comet theory appeared to offer a good
explanation.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo and appearing in General Chemistry by Whitten,
Davis, and Peck, submitted for their 1996 fifth edition, Saunders
College Publishing.
METRIC VS. ENGLISH: PROS AND CONS
Most people believe that, except for the United States, the
world is 100% metric. This is not true. There are many
scientific and nonscientific measurements made today that are not
metric and will probably never be metric. These include: (1) the
60-second minute, (2) the 60-minute hour, (3) the 24-hour day,
(4) the 7-day week, (5) the 31-day month, and (6) the 365 day
year. In addition, the majority of world trade is also based
upon nonmetric measures, for example: (7) world oil production is
measured in barrels (there are 44 gal per U.S. oil barrel), (8)
lumber is sold by the board foot, (9) all farm products marketed
throughout the world are measured in bushels (there are 8 gal in
a bushel), in pecks (2 gal per peck), and by the hundred weight
(2000 lb equals 20 hundredweight [20 cwt] equals 1 short ton),
(10) silver, gold, platinum, copper, iron, and zinc are sold by
the troy ounce (12 troy ounces equals one troy pound), (11) eggs
are sold by the dozen, not in groups of 10, (12) European
draftsmen have use quarter-millimeters because a tenth of a
millimeter is too small for pencil and paper renderings.
Many people believe that in everyday use the Fahrenheit
temperature scale is superior to the Celsius (centigrade)
temperature scale because the Fahrenheit scale, between 0o F and
100o F, spans almost the entire range of hot and cold in a
temperate climate. The same range on a centigrade scale spans a
range that doesn't quite go low enough. Most winter temperatures
in a temperate climate fall below 0oC, the freezing point of
water, which necessitates the frequent use of negative
temperatures. The temperature of a temperate climate rarely goes
over 40oC, leaving 60% of the Celsius temperature scale unused in
everyday life.
Many measures of length are derived from the human body,
making them somewhat universal. For example, almost every
civilization (including China, Egypt, and Greece) has measured in
terms of feet.
We're not suggesting that the United States refuse to adopt
the metric system because we already have in areas such as
international business and science. Also, our English system is
based upon the metric system. For example, one inch is defined
as exactly 2.54 cm, and one calorie is defined as 4.187 joules.
But there's nothing wrong in also using the English system where
it makes more sense in everyday life.
Adopted from an article written by Ronald
DeLorenzo appearing in Problem Solving for General Chemistry,
1993, Wm. C. Brown Publishers.
A CAR REFRIGERATOR IN A CAN
If you dread entering your car on hot summer days, you will
appreciate a new, patented product that cools car interiors from
130oF to 77oF in seconds. Unlike some high-tech refrigeration
systems, this supper-fast car cooler comes in a spray can. As
you expel its contents into your car interior, the discharged
liquid quickly evaporates. According to the inventor, because
evaporating liquids decrease their average kinetic energy by
losing their higher-energy molecules, they lower their own
temperature and that of their surroundings. More importantly
however, before a liquid can evaporate, energy is needed to
overcome the attractive forces holding the liquid molecules
together. If the surroundings supply that energy, the
temperature of the surroundings decreases.
The product's name is Instant Car Kooler , and two 16-ounce
cans sell for about $10. The liquid used by Instant Car Kooler
is nothing more than a mixture of 90% water and 10% ethyl
alcohol, but dispensing this liquid as a fine mist to insure
rapid evaporation requires a special nozzle. By decreasing the
mist droplet size, the special nozzle increases the overall
surface area of the expelled solution, hastening evaporation and
cooling.
Since one gram of evaporating water absorbs 2360 joules of
heat from its surroundings, one 16-oz (454 g) can of Instant Car
Kooler has the capacity of absorbing about one million joules.
You have probably witnessed this extraordinary heat-absorbing
capability of water during short showers on hot summer days. As
the rain falls, outdoor temperatures immediately plummet.
The next time you encounter an unbearably hot car, you don't
have to drive several minutes with the car windows fully opened
waiting for the car to cool. Neither do you have to rev up the
engine, turn on your air conditioner, leave the car, and wait in
a cool spot until the car cools off. Instead, just reach into
the glove compartment, take out your refrigerator in a can, and
spray yourself instantly into a cooler environment.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo and appearing in General Chemistry by Whitten,
Davis, and Peck, submitted for their 1996 fifth edition, Saunders
College Publishing.
ADOLF HITLER'S DIARIES: A MODERN DAY CON GAME
In the early 1980s, publishers of Stern, a leading West
German weekly magazine, paid about four million dollars for what
they believed were Adolf Hitler's diaries. Stern purchased the
sixty-four volumes of diaries after first having handwriting
experts analyze the documents for possible forgery. The forged
diaries appeared so genuine, however, that they fooled those
experts. Chemical analysis is another method that can be used to
test for authenticity, and chemical tests showed that the diaries
were fraudulent. Although some chemistry is very sophisticated,
you would be surprised as to how much chemists discover with
simple chemical tests. The chemical analysis of the diaries is
an illustration of this. Chemists know that most chlorides (such
as sodium chloride which is table salt) are soluble in water.
There are three exceptions, one of which is silver chloride.
Chemists used this simple solubility rule in one of the tests
performed on the Hitler Diaries.
The ink used in the Hitler Diaries contained chloride ions.
When you apply such an ink to paper, the chloride ions migrate
through the paper away from the original ink lines for about two
years. The maximum migration distance is only about 3 mm from
the original point of ink application.
Chemists soaked pages of the Hitler Diaries in a silver
nitrate solution to locate the chloride ions. Silver ions react
with chloride ions to form insoluble silver chloride. Since
silver chloride is insoluble, it doesn't wash off the paper when
the paper is placed in the silver nitrate solution. When freshly
made, silver chloride is white. When exposed to light, the white
silver chloride turns black as it decomposes into silver atoms
and chlorine molecules. We take advantage of this when we use
silver salts in photographic film.
Using a microscope, chemists carefully examined the lines of
ink in the diaries that were treated with silver nitrate. They
saw small black specks of silver surrounding the original ink
lines. All black specks of silver were less than 3 mm away from
the original ink lines. Since it takes two years for the
chloride ions to migrate 3 mm away from the original ink lines,
the diaries that the chemists examined had to be less than two
years old. Hitler died in 1945, therefore the diaries should
have been several decades old and the chloride ions in the ink
would have migrated the 3 mm distance from the ink lines.
Think what might have happened without those chemical tests.
Historians would have accepted the diaries as historical
documents, and researchers would have wasted untold numbers of
man-hours studying them. Your history courses would contain
incorrect information and interpretations.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo appearing in General Chemistry by Kask and Rawn,
1993, page 148, Wm. C. Brown Publishers.
AIR POLLUTION--INDOORS
The effects of industrial and household chemicals on the
environment--air, water, and soil--have concerned chemists for
several decades. Recently, chemists have realized that our
homes, schools, and workplace are the environments in which we
spend 90% of our lives, and that these environments can be more
polluted than our smoggy streets.
Uranium-bearing soils, which lie under many buildings in
some regions, exude a radioactive gas, radon. We build our
houses with plywood and adhesives and insulate them with plastic
foam, all of which contain volatile formaldehyde. Then we paint,
carpet and tile our buildings with materials that require organic
solvents in their use or manufacture, and scrub them with
household cleaners that contain ammonia (a biological poison) and
phosphoric acid. In summer we control pests with insecticides
and in winter we heat with furnaces, which, when they get old,
give off carbon monoxide. And all year we cook over invented
stoves, taking in more carbon monoxide along with some nitrogen
oxides. After dinner, we dress for an evening out, using
antiperspirant sprays and various cosmetics. Does anyone in your
house smoke? Add nicotine and tar. An Environmental Protection
Agency study showed that typical indoor concentrations of all
target chemicals exceed outdoor levels by factors of up to 100.
Of course, some of these pollutants have been present indoor
since we first lived in buildings. Our modern problems stem from
trying to save energy by using tight-fitting windows and doors,
which trap pollution indoors.
As buildings have become more airtight, a new illness called
"sick building syndrome" has appeared with increasing frequency.
Symptoms are similar to those suffered by people living in
contaminated air: hoarseness, stinging eyes, headaches, nausea,
and lethargy. But there may also be a problem with "mind
pollution." According to one study, people who dislike their
jobs are much more likely to suffer from sick building syndrome
than people who like their jobs. Sick building syndrome probably
reflects a combination of psychological and chemical factors.
Until solutions are found for these problems, we will need
literally to go out for a breath of fresh air and find jobs that
we can enjoy.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo appearing in Understanding Chemistry, An
Introduction by Dewey, 1994, page 10, West Publishing Company.
HAIR ANALYSIS: FROM LEARNING DISABILITIES IN CHILDREN TO
ADULT DRUG ABUSE
Hair analysis may become a frequently used and valuable tool in
early disease detection programs. Hair normally contains
relatively fixed amounts of several trace elements, such as
calcium, magnesium, potassium, sodium, cadmium, cobalt, copper,
iron, lead, manganese, zinc, chromium, lithium, and mercury.
Abnormally high or low concentrations of these and other elements
in the hair can be an indication of many abnormalities or
diseases, such as air and water pollution, cystic fibrosis, diet
deficiencies, diabetes, Down's Syndrome, schizophrenia, and
learning disabilities. Crime labs can also detect certain drugs
in the hair, such as barbiturates, amphetamines, morphine, and
heroin. It is also possible to determine the approximate time
when the drug was taken or injected.
Hair analysis has many advantages over the more widely used
blood and urine analyses. Collecting hair is less painful and
less embarrassing. Hair can be stored for longer periods without
deterioration. (It is this storage advantage that make the
investigation of Taylor's "assassination" possible.) Also,
substances are accumulated in hair with a concentration of at
least ten times that found in blood or urine. Adopted from an
article written by Ronald DeLorenzo appearing in Problem Solving
for General Chemistry, 1993, Wm. C. Brown Publishers.
MINING FOR INVISIBLE GOLD
If you've seen any western movies about the gold rush era of
the 1800s, you probably remember scenes depicting prospectors
panning for gold. The expression "panning for gold" refers to
the age-old practice of swirling a water and soil slurry in a
shallow pan. Since gold is almost 8 times more dense than most
dirt and rock samples, any free gold present in the dirt would
remain behind as the swirling water washed the less dense
sediments over the edges of the pan. This method worked well
when gold was plentiful enough to be found in nuggets and flakes
large enough to be easily seen with the naked eye. Now that gold
is less plentiful, a one-ton rock pile containing only 1/10 of an
ounce of gold is considered to be a rich source of this precious
metal. Unfortunately, such infinitesimal amounts of gold are
invisible to the naked eye, and panning for gold has become a
worthless technique to separate the gold from the rock.
Special chemical methods have been developed to extract the
minuscule quantities of gold present in gold ore. The first step
performed to separate gold from its ore is to crush the gold-
containing rock and then to use special chemicals to get the gold
into solution while leaving the rest of the rock behind.
In the final step, electroplating is used to recover the
dissolved gold. An electric current is allowed to flow through a
wire inserted in the gold solution. The electric current forces
the gold to come out of solution as a pure solid metal.
Because gold is not as plentiful in nature as it was only a few
decades ago, as many as ten tons of rock may have been processed
for every one ounce of gold jewelry you wear.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo appearing in Understanding Chemistry, An
Introduction by Dewey, 1994, page 517, West Publishing Company.
TAMING DANGEROUS CHEMICAL SPILLS WITH BAKING SODA
Early one Sunday morning in 1983 just outside of Denver,
Colorado, a train carrying a tank car filled with thousands of
gallons of nitric acid was punctured by the coupling of another
rail car. Over 22,000 gallons of nitric acid spilled onto the
ground. Five thousand residents living within a 500-block area
around the nitric acid spill were evacuated. However, because of
some chemical know-how, the availability of snow blowers from a
nearby airport, and the excellent efforts of Denver fire
fighters, there were no fatalities or serious injuries, and no
major environmental damage. The fire fighters used airport snow
blowers to blow a relatively harmless chemical similar to baking
soda onto the nitric acid and neutralized it. In fact, they
could have even used baking soda. Let's see why.
We know that acids can be neutralized by bases such as
sodium hydroxide. Baking soda can also neutralize acids. In
fact, many people use baking soda to neutralize their excess
stomach acid. There is an advantage to using baking soda instead
of sodium hydroxide. If the fire fighters used too much sodium
hydroxide to neutralize the acid, the excess sodium hydroxide
left behind would also pose an environmental and human health
threat. Sodium hydroxide, also known as lye, is an extremely
caustic chemical that is used in oven cleaners and chemical drain
un-stoppers. On the other hand, few people would be overly
concerned if there was some extra baking soda left on the ground
after the nitric acid was neutralized.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo appearing in Understanding Chemistry, An
Introduction by Dewey, 1994, page 308, West Publishing Company.
SOLIDS THAT ARE LIGHTER THAN AIR
What would you think if you saw a bar of soap floating in
mid-air? Is it a magician's trick? We instinctively know (and
can also see in Table 1-8), that the densities of solids are
usually more than the densities of gasses. However, chemists
have recently created solids called SEAgels and aerogels that
are less dense than air. Why are these solids so light, how are
they made, and how can they be used in your home?
SEAgels are prepared in much the same way as gelatin
desserts (for example, Jell-OTM). When making a gelatin dessert,
gelatin (an animal protein) is first dissolved in hot water and
then cooled. Upon cooling, the mixture sets to form a flexible
solid called a gel. The gel is made up of a thin-walled honey-
combed network of protein (the gelatin) whose spaces are filled
with water. If we could evaporate the water from the gelatin
dessert and leave the honey-combed protein network behind, a very
light-weight solid would form. However, when evaporating water
from a gelatin dessert, the attractive forces between the water
and the solid network cause the gel to shrink as the water
evaporates.
SEAgel is made by dissolving agar (a gelatinous material
prepared from certain saltwater algae and used for thickening
foods) in a water-organic solvent mixture and then letting it
cool. Upon cooling, this mixture also sets much like Jell-OTM.
Also like Jell-OTM, if we tried to evaporate the water from this
gel, the solid agar network would shrink. However, the gel could
be freeze-dried without shrinking it.
When freeze-drying, chemists first freeze the gel to lock
its shape in place, then place the frozen gel into a combination
freezer and vacuum chamber to evaporate the water. After the
water evaporates, the delicate honeycombed agar structure remains
with its spaces filled with air. Although it would be more
correct to call this resulting substance a foam, most people
continue to refer to such foams as aerogels.
The density of SEAgel is about 1.5 g/L, and, as shown in
Table 1-8, the density of carbon dioxide is about 1.9 g/L. This
difference in densities allows us to do an interesting
demonstration with a soap-bar sized sample of SEAgel, an aquarium
tank, and carbon dioxide gas. First half-fill the aquarium tank
with carbon dioxide. Because carbon dioxide is more dense than
air, carbon dioxide will displace the air in the tank and sink to
cover the tank bottom. Then drop the white soap-bar shaped
sample of SEAgel into the tank and watch as it falls to the
bottom of the tank and then floats to the top of the carbon
dioxide layer.
Like all foams, solid aerogels are excellent insulators. In
fact, aerogels have the best insulating properties known of any
solid. Because of this, one California company has begun using
aerogels as insulating material in refrigerators.
Reprinted with permission. Adopted from an article written by
Ronald DeLorenzo and appearing in General Chemistry by Whitten,
Davis, and Peck, submitted for their 1996 fifth edition, Saunders
College Publishing.
WHY ALCOHOL AFFECTS WOMEN MORE ADVERSELY THAN MEN
Alcohol consumption has played a significant role in human
culture, and its use can be traced back to the earliest recorded
chronicles. More recently, several studies have shown beneficial
health effects associated with the moderate use of alcohol.
According to recent studies, the heart disease death rate for men
(not women) decreases with increasing alcohol consumption up to a
maximum of four drinks a week. However, the male cancer death
rate increases with increasing alcohol consumption and is
significantly higher when men consume four drinks per week rather
than one. On the other hand, women can safely drink only about
half as much as men to get the same heart benefits.
Nevertheless, the increase in alcohol-induced cancer (including
breast ca