December, 2006 - Buckeye Valley Local Schools

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DECEMBER 2006

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Also Inside:Unusual Sunken Treasures

Also Inside:Unusual Sunken Treasures

2 ChemMatters, DECEMBER 2006

Production TeamCarl Heltzel, EditorCornithia Harris, Art DirectorLeona Kanaskie, Copy EditorMichael Tinnesand, Contributing Editor

Administrative TeamTerri Taylor, Administrative EditorSandra Barlow, Senior Program AssociatePeter Isikoff, Administrative Associate

Technical ReviewSeth Brown, University of Notre DameDavid Voss, Medina High School, Barker, NY

Teacher’s GuideWilliam Bleam, EditorDonald McKinney, EditorMark Michalovic, EditorRonald Tempest, EditorSusan Cooper, Content Reading ConsultantDavid Olney, Puzzle Contributor

Education DivisionMary Kirchhoff, Acting DirectorMichael Tinnesand, Associate Director for AcademicPrograms

Policy BoardDoris Kimbrough, Chair, University of Colorado–DenverRon Perkins, Educational Innovations, Inc., Norwalk, CTBarbara Sitzman, Tarzana, CA Ingrid Montes, University of Puerto RicoSusan Gleason, Middletown, DE

ChemMatters (ISSN 0736–4687) is published four times ayear (Oct., Dec., Feb., and Apr.) by the American ChemicalSociety at 1155 16th St., NW, Washington, DC 20036–4800.Periodicals postage paid at Washington, DC, and additionalmailing offices. POSTMASTER: Send address changes toChemMatters Magazine, ACS Office of Society Services,1155 16th Street, NW, Washington, DC 20036.

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By Bob BeckerQuestion From the Classroom

http://chemistry.org/education/chemmatters.html

Q: We learned in class that all objectshave mass—even a helium balloon. So whythen does a helium balloon rise?

A: The answer most often given to yourquestion has to do with density. Just as apiece of wood will float upward in a lakebecause it is less dense than the water, so toowill a helium balloon rise in the room becauseit is less dense than the surrounding air.Although there is certainly truth in that expla-nation, it really isn’t the whole answer. Ahelium balloon does indeed have mass, andthe force of gravity would therefore make itaccelerate downward—toward the center ofthe earth. There must be some greater forceacting on it in the opposite direction to make itaccelerate upward. And there is; it is known asa buoyant force, and it acts on every object inthe room, not just those that are less densethan air.

That buoyant force is rather small, onlyenough to lift about 0.0028 pounds (1.3 g) for every liter of air the object dis-places. For most things around us that wemight try to lift—a desk, a glass of water, achemistry textbook, a friend—the buoyanteffect is so slight that you would certainlynever notice, but it is still there. What thismeans is that you actually weigh more thanyou think you do! Let’s say you weigh 154pounds—at least that’s what you think youweigh. You would displace about 70 L of air.This translates into a buoyant force upward ofabout 0.200 pounds* coming from the sur-rounding air.

70 L ! 0.0028 lb/L = 0.196 lb, or 0.200 lb

Take that air away, and you take awaythe buoyant force. So if you lived in a vacuum(a place with no air or gas of any kind to buoyyou up) and you stepped onto a sensitiveenough scale, it would show your “true”weight: 154.2 pounds. Hopefully, that wouldnot be cause for alarm—certainly, if you livedin a vacuum, you’d have more to worry aboutthan a little weight gain—but it is somethingto think about.

But, what if instead of being a 70-L per-son, you were a 70-L helium balloon!? Thehelium inside you would weigh about 0.027

pounds and the balloon itself would probablyweigh another 0.040 pounds, for a total “true”weight of 0.067 pounds, as measured in avacuum. Now, factor in the air, and that0.200-pound buoyant force acting upward onyou makes a huge difference. In fact, it wouldgive you a negative apparent weight: –0.133pounds, which is why you would find yourselfaccelerating upward toward the ceiling.

But where exactly is this buoyant forcecoming from? Well, if you have learned aboutgases, then you are probably familiar with thefact that gas molecules exert pressure in alldirections as a result of their continuous bom-bardment with surrounding surfaces. You arealso probably familiar with the fact that thepressure exerted by the atmospheredecreases at higher elevations. The higher upone goes, the thinner (less concentrated) theair is. With fewer molecules colliding, the col-lective force is weaker. This is certainly truefor the air at the top of the mountain—theatmospheric pressure at the top of MountEverest is about 70% lower than it is at sealevel. But it is also true, to a much lesserextent, for the air at the top of a room. Thismeans that there are slightly more air mole-cules per second hitting the bottom of anobject and pushing it upward than there arehitting the top of the object and pushing itdownward. There are also molecules hittingthe sides of the object, but their forces effec-tively cancel each other out. This is most eas-ily understood if we simplify the object bymaking it rectangular as shown in the figurebelow. The forces acting on the right would beevened out by the forces acting on the left. Butthis would not be true for the forces acting onthe top and bottom; they would add up to atotal force upward, and this is what we call thebuoyant force.

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So how exactly does density enter intothe picture? It turns out that the buoyantforce acting upward on an object is exactlyequal to the weight of the fluid (air, water,whatever!) that is being displaced. This issometimes referred to as Archimedes’ princi-ple. Because a liter of air weighs 0.0028pounds, a one-liter object displaces thatmuch air and has a buoyant force actingupward on it of 0.0028 pounds. If the objecthas the same density as air, it would have atrue weight of 0.0028 pounds. With thebuoyant force factored in, it will have anapparent weight of precisely 0 pounds. Thatis, it will be neutrally buoyant, neither float-ing nor sinking. If the object is denser thanair, its weight will be greater than the buoy-ant force; it will, therefore, have a positiveapparent weight, and accelerate downward.And if the object is less dense than air, itsweight will be lower than the buoyant force;it will therefore have a negative apparentweight and accelerate upward.

Now, here’s one more thing to thinkabout: when you make a sharp turn in a car,you and everything else in the car tend to goflying outward. Right? Not necessarily. If oneof the objects in the car is a helium balloon,you might be in for a surprise. Check outwhat it does. But please, make these observa-tions from the passenger seat, not whileyou’re driving! See if you can explain why itbehaves that way.

*The metrically minded students outthere may be wondering why pounds arebeing used instead of grams or kilograms.Because this article pertains to forces, theauthor decided to stick with pounds, whichtruly are units of force. Grams and kilogramsare not units of force. And although 0.200pounds translates into 90.8 grams, it wouldbe inappropriate to talk about a 90.8-gramforce. The correct translation would be intonewtons (a 0.89 N force)—the metric unit offorce, but for those students who have notyet had a course in physics, a newton wouldonly conjure up images of fig-filled wafers!

Question From the Classroom 2Why does a helium balloon rise?

Corn—The A”maiz”ing Grain 4A grain intimately familiar yet mysterious, we have formed apartnership with corn for over 8000 years. You’ll be surprised to learn how thoroughly corn is embedded into modern life.

ChemSumerSticky Situations: The Wonders of Glue 8Glue: handy tool or childhood snack? You’ll be the judge afterreading all about the wild world of glue.

Unusual Sunken Treasure 11The Swedish schooner Jonkoping was attacked by German U-boats in 1916. The sunken ship lay undisturbed in herunderwater resting place for more than 80 years until treasurehunters discovered her. Unusual treasure indeed. Not gold orsilver, but champagne! Could the bottles be brought to thesurface without “blowing their corks?”

Thermometers 14Your head is burning up, and you suspect a fever. Along with two aspirin you swallow … a thermometer? Take a look at some common and not-so-common instruments for measuringthe average kinetic energy of our molecules.

ChemHistoryThe Race for Iodine 18Who knew scientists could drum up so much drama? An exposéon the backroom dealings and strange characters involved in thediscovery of new elements.

Chem.matters.links 20

CMTEACHERS! FIND YOUR COMPLETE

TEACHER’S GUIDE FOR THIS ISSUE ATwww.chemistry.org/education/chemmatters.html.

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CornThe A”maiz”ing Grain

he popularity of corn cannot bedenied. As Dr. Paul Mangelsdorfsays in his book Corn: Its Origin,Evolution, and Improvement: “Itis the most efficient plant that wehave for capturing the energy of

the sun and converting it into food. True, weconsume directly only small amounts of corn:roasting ears, breakfast cereals, Indian pud-ding, and, for a somewhat different purpose, abeverage invented by a Kentucky minister ofthe Gospel, bourbon whiskey. But trans-formed, as three-fourths of it is, into meat,

milk, eggs, and other animal products, it isour basic food plant, as it was of the peoplewho preceded us into this hemisphere. Cornis as important today as it was for our nativepeoples.” Native American legend has it thatcorn is of divine origin—the food of the godsthat created the earth.

But as in many other instances, modernhumanity has managed to stir up controversywith this “perfect” gift. Today, genetically mod-ified corn, gasohol from corn, and even highfructose corn syrup have become sensitiveissues with people taking sides. Meanwhile,industry leaders call corn a future “manufac-turing plant”—pun intended; the list of corn-based products is constantly increasing.

The Spanish called it “maíz,” and thebotanical term became Zea mays. The Englishword was a bad choice, because “corn” refersto different grains in different places. Thename gaining popularity among scientiststoday is “maize.”

In less than a thousand years—cyber-speed by evolutionary standards—tiny “ears”of corn were growing all over Central Amer-ica. Long before Columbus or Cortez arrived,corn had become a major food crop acrossboth American continents. The explorers car-ried ears back home, and within another 100

years, corn spread as far as China. Now, cornis cultivated on six continents and is har-vested in more countries than any other single crop.

We need corn andcorn needs us

Corn has partnered with humans formore than 8000 years. Early Mesoamericanwall paintings tell of the food’s “discovery,” in the flatulence of a fox. In a commonMesoamerican myth, a fox follows an antinside a large mountain or boulder where thefox discovers a cache of maize. After eatingthe grain a vision of a wondrous new food was made evident in the haze of the fox’s flatulence!

There is a legend that old-timers tell of one

particular summer when it got so hot that the

corn in the fields startedpopping right off the

stalks. The cows and pigsthought it was a snowblizzard, and they lay

down and froze to death.

By Gail Haines

4 ChemMatters, DECEMBER 2006 http://chemistry.org/education/chemmatters.html

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Possibly, a more likelyscenario is that in ancientMexico, people practicedselective breeding on a grasscalled teosinte the old-fash-ioned way. By only using thebest/biggest/sweetest seeds,the ancestors of modern cornevolved over time. Peoplehave been modifying thegenetics of crop plants sincetime immemorial by this typeof selective breeding.

People needed maize tosurvive. Vegetarians, takenote! Combined with beansand squash—the way nativetribes prepared it—corn sup-plies all the amino acidsneeded for a healthy diet. Andcorn needs people, becausethe ears can’t reseed them-selves. Farmers must removethe kernels from the cobbefore they can be planted inthe ground, and the seedlingsmust be nurtured for them togrow.

Consider a typical fastfood meal: hamburger, fries, and a soft drink.The single food that links all these is … youguessed it, corn to feed the beef, corn syrupin the soft drink, the bun, and the ketchup,and corn oil to fry the potatoes. Every day, theaverage American eats around two pounds ofcorn in the form of dairy products and meatproduced from corn-fed cows, not countingroasted ears, muffins, cereal, chips, and the56 quarts of popcorn each of us consumeevery year. Much of it is grown in 12 contigu-ous Corn Belt states around Illinois.

Now for the biologyMaize is a cross-pollinating annual grass,

with a tall stalk, male tassels, and female ears.Seeds consist of an oily germ and anendosperm composed of starch and protein.The outer shell or hull of the seed is the peri-carp. Hundreds of different varieties still growin rural Central America, with kernel colorsranging from white to purple. But most culti-vated strains fall into five types (with the per-cent of commercial crops devoted):

1. Popcorn—the original cultivated corn.Moisture in the starchy core explodeswith heat into, arguably, the world’s old-est snack food (<1%)

2. Sweet corn—more sugar than starch.Add salt and butter (<1%)

3. Flour corn—soft. Makes great tortillas(12%)

4. Flint corn—hard. Grows in colderweather, used industrially and for live-stock feed (14%)

5. Dent corn, a flint/flour cross, accounts fora whopping 73% of commercial crops.The starchy interior feeds livestock andprovides raw materials for the chemicalindustry. In the United States, much of itis genetically engineered.A sixth type of corn called pod corn is

only used for research. Each kernel has itsown husk, so it is too labor intensive to usecommercially.

Genetically modifiedcorn—isn’t thatfrankenfood?

Who eats genetically modified or trans-genic (GM) corn? If you live in the UnitedStates, you do. Cows, pigs, chickens, anddogs do too. Some 70% of the processedfood on grocery store shelves contains geneti-cally modified corn and other plants in usesince the early 1990s. In the United States,GM foods are considered “nutritionally identi-cal” to the ordinary kind, so they are not nor-mally labeled.

How does genetically modified comparewith selective breeding? Well, selective breed-ing is really just a primitive form of genetictinkering. A farmer must choose a male and afemale plant, hoping that the gene responsiblefor a desired trait is transferred to their off-spring. The breeder can only guess, however,that the desired gene is present in the parentplants based on visual inspection; there is noguarantee that the offspring will indeed havethe desired traits. Success in selective breed-ing only comes after a long trial-and-errorprocess.

Genetic engineeringis a more targetedapproach, allowing thebreeder to take selectedgenes from one organ-ism and place them intoanother. The offspring inthis case is called agenetically modifiedorganism (GMO), or a transgenic organism.This is pretty straightforward and direct—plus, it allows something the selective breedercan never accomplish—genes from onespecies can be transferred to another, differ-ent species. Want grape-flavored corn? Not aproblem, but impossible with selective breed-ing. But seriously, although the process is notquite that simple, enhancing flavor, cropyields, and resistance to herbicides are desir-able traits that have already been engineeredinto GM corn. Genetic engineering has alsoallowed the incorporation of a gene that codesfor the Bacillus thuringiensis toxin, protectingcorn plants from insects.

Genetic modification may sound like biol-ogy, but chemistry makes it fly. DNA mole-cules get cut and pasted by chemicals calledrestriction enzymes, and “gene guns” shootgene-coated, microscopic particles of gold ortungsten directly into plant cells. Again, it isnot as simple as injecting a single gene intothe plant’s cells. A combination of genes frombacteria, viruses, andthe gene from thedonating organism isassembled. The bacter-ial and viral genes areused to break downbarriers between thetwo species beingcrossed, and they allowa mechanism for mak-ing sure the desiredgene is incorporated.As the genes areinjected into the plant’scells, it is suspectedthat the injection trig-gers a wound responsewhich helps its DNAintegrate the new gene.With the new genes onboard, one may engi-neer increases in thecorn’s productivity, orprotein concentrationor whatever is desired.

A qualitative test for GM corn. Hybrid cornsamples turn test solution dark blue, whilenormal kernels do not.

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Sounds great … whyisn’t everyone onboard?

Europeans are not fond of GM crops;only within the last two years have GM cropsbeen allowed in Europe, where each productmust display a special GM label. And in spiteof the United Nations official support, manydeveloping nations still are hesitant to con-sume GM crops, including corn. GM agricul-ture has had bad press around the world;some activists call it Frankenfood. Many peo-ple are not interested in eating unnatural food;corn is not supposed to taste like grapes!

Also, there are fears that unpredictableresults may occur when multiple copies of aforeign genetic code are injected into theplant. Critics of genetic engineering fear thatnew pathogens may be created within theplant, including bacteria that will be resistantto available antibacterial drugs.

Experimental attempts to coax corn intoproducing protein-based drugs and vaccinesinside the kernel are called “pharming.” Thisprocess is thought by some to be safer andcheaper than growing drugs in animal cell cul-tures. But in 2002, “pharm” corn that wasengineered to produce a pig vaccine slippedinto food fields by accident. In another case,some untested GM corn was processed intotaco shells before the mistake was caught; noone ate any of the shells and the foods weredestroyed. Still … corn pollen spreads far andwide, riding on the wind and farm machinery.Transgenic strains have been found fertilizingother varieties. Scientists are supposed to testevery new strain for possible allergens. Somepeople are worried that new “superweeds” orresistant insects will develop in response togenetic tinkering with nature.

You don’t want pig vaccine in your taco,and preserving genetic diversity is very impor-tant, but transgenic plants are already con-trolled far more rigorously than other foods.Fear of GM corn is costing lives in a fewAfrican countries that have refused Americanfood donations because they contain GMproducts, which Americans eat every day. Sci-entists try to stay ahead of the game, develop-ing corn strains that are sterile and evenstrains that grow underground, where nopollen can escape.

EthanolEthanol, the chemical name for ethyl

alcohol, CH3CH2OH, is in beer, whiskey, andwine and is one of the first chemicals peoplelearned to make. Corn whiskey was the origi-nal “White Lightning” of Prohibition days. Thelargest volume corn-based product on themarket today is fuel-grade ethanol—4 billiongallons of it is made each year. You alreadyburn some “gasohol” in your tank. All carsnow sold in the U.S. can handle a 15%ethanol, 85% gasoline fuel mix. “Flex-Cars”can burn at least 85% ethanol—E-85. The2007 Indianapolis 500 will run on 100%ethanol fuel made from corn—bringing newmeaning to “lightning fast!”

Ethanol burns cleaner than gasoline, producing little to none of the black, sootysmoke you see pouring out of an old car’sexhaust pipe.

CH3CH2OH + 3 O2 ! 2 CO2 + 3 H2O

Both ethanol and gasoline produce car-bon dioxide when burned, which becomesatmospheric “greenhouse gas” pollution. Butthere is a difference—corn captures CO2 fromthe air as it grows. Petroleum-based fuels, onthe other hand, release tons of CO2, whichhave been trapped underground for millionsof years.

You may have heard gasohol productionuses more energy than it provides. Critics

count every BTU of energy used to producethe gasohol, grow the corn, make the fertilizer,irrigate, and even build the farm machinery.Proponents use the newest technological datafor growth and production, and then they sub-tract coproducts made from corn protein andcorn oil and the energy value of sunshine. Acradle-to-grave analysis of the costs of pro-ducing ethanol would be a useful exercise,perhaps one that might be suggested by yourteacher. What we do know is that, thermody-namically, every energy conversion uses moreraw energy than it produces in fuel. The gainis convenience: coal to electricity, crude oil togasoline, corn to ethanol. Better technologyfavors the proponents, and ethanol already isreplacing gasoline-from-petroleum at an ever-increasing rate.

Oh, the sweet tasteof—corn?

Along with CO2 in your can of soda, thesweetener is almost certain to be pure corn.High fructose corn syrup (HFCS) is corn’smajor refined foodproduct.

Corn syrup,mostly glucose, is notvery sweet. Tablesugar (sucroseC12H22O11)—with eachmolecule composed ofone glucose and onesuper-sweet fruc-tose—has the taste welove. Food chemistsfound ways to get that taste from corn. Theyincreased the fructose level in corn syrup to42% (HFCS-42), 55% (HFCS-55) or 90%(HFCS-90), to make it as sweet as—orsweeter than—table sugar.

The 42% fructose syrup is produced byadding an enzyme that interconverts glucose

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and fructose; the 42% fructose/58% glucoserepresents the equilibrium ratio. The 90%fructose syrup is produced by a partial sepa-ration of the two sugars using a column thathas a high affinity for fructose. The 55% fruc-tose syrup is made from blending the 90%and the 42% and seems to be the standardsweetener for products such as soft drinks.

HFCS is cheaper than sucrose. It also pro-motes browning in bread, makes cookieschewy, prevents freezer burn, preserves cannedfruit texture, enhances flavors, and more. HFCSis in ketchup, hamburger buns, bacon, lunchmeat, whole wheat bread, and products youwould never suspect had sugar at all.

PopcornLong, long before there were movies

there was popcorn. Popcorn thought to be5,600 years old was found in a cave in centralNew Mexico. Today’s typical American eatsover 50 liters of popcorn each year. AndAmericans don’t just eat the stuff — they arethe world’s largest producers. Most of theworld gets its popcorn from the U.S. Midwest:Indiana, Iowa, and Nebraska.

A popcorn kernel is simply a seed withthree parts: the germ is the part that sproutsout of the seed during growth; the endospermis the starch that expands during the poppingprocess; and the pericarp, or outer hull, whichis made partly of cellulose. Now, not all cornhas the potential to pop. The maize must havethe right type of pericarp to produce the fluffyfood. The pericarp needs to keep moisturetrapped inside the corn kernel while it’s beingcooked. As the temperature of the kernelincreases, the pressure exerted by thegaseous H2O inside the kernel also increases.Once the internal pressure exceeds that out-side and the pericarp can no longer withstand

the force, the kernel splits open, turning thekernel inside out.

No one likes chomping down on un-popped kernels. The highest quality popcornhas a pericarp with a highly ordered crys-talline arrangement of its cellulose molecules.The two main reasons why kernels don’t popis they have insufficient moisture, or that thehull leaks. The ideal popcorn has about 14%moisture and must be stored in a tightlysealed container so it won’t dry out.

Eating popcorn is typically considered tobe a healthy act. It is fat-free, low in calories,and provides fiber. And it’s natural — accord-ing to the Popcorn Board (a nonprofit groupof popcorn processors), there is no geneti-cally modified popcorn currently available forsale in domestic or international markets.

Increased use ofHFCS = increasedsize of American?

Now HFCS is getting blamed for makingAmericans fat. Is this true? Or is it “Franken-fat”? Evidence shows today’s average Ameri-can is heavier than previous generations, andthe time frame of the weight increase—sincethe mid-1970s—matches the huge spike inHFCS use. But over the same 30 years,among other things, Americans have super-sized their diets, averaging 300 extra caloriesa day.

Chemically, HFCS-42 and HFCS-55 aresimilar to sucrose at 50–50%, but the bodyhandles extra glucose or fructose differently.Glucose is used directly by the body’s cells;fructose goes first to the liver. Glucose spikesa surge of insulin and also leptin, a hormonethat signals you have eaten enough. Fructosedoesn’t, so you may just keep eating! Fruc-

tose you don’t burn for energy and convertseasily into body fat.

Research is under way. Meanwhile, ifweight is a problem, avoiding those 32-ounce“super” drinks—sweetened with HFCS orsucrose—would be a no-brainer.

Solving controversy can superchargescience. Maize is already a great humanachievement—8000 years and still growing.Watch for further developments.


In American Indian folk-lore, some tribes were

said to believe thatquiet, contented spiritslived inside of each pop-corn kernel. When their

houses were heated,the spirits would

become angrier andangrier, shaking the

kernels, and when theheat became unbear-able, they would burstout of their homes and

into the air in a disgrun-tled puff of steam.

REFERENCESMangelsdorf, P. Corn: Its Origin, Evolution,

and Improvement, Belknap Press,Cambridge, MA, 1974.

Tandjung, A., et al. Role of the pericarp cel-lulose matrix as a moisture barrier inmicrowavable popcorn.Biomacromolecules, 2005, 6, 1654–60.

Other information courtesy of Linda Stradleyand her web site, What’s CookingAmerica, athttp://whatscookingamerica.net.

Other references may be found in theTeacher’s Guide.

Gail Haines is a science writer and book authorfrom Olympia, WA. Her most recent article,“Honey: Bee Food Extraordinaire,” appeared in theDecember 2005 issue of ChemMatters.

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The ins and outs of popcorn.

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For many of us, the allure ofglue peaks during early ele-mentary school. We eat it as aforbidden delicacy, we use itto create seasonal construc-

tion paper crafts, and some of us mayeven use the colored varieties tospice things up. After, say, secondgrade, most individuals forget aboutglue. The initial fascination evapo-rates, and, instead, we begin takingthe sticky stuff for granted. In actual-ity, however, glue deserves far moreattention. It comes in many forms, isderived from surprising sources, andfulfills a plethora of functions.

Creatures thatstick and stickystuff from creatures

What do mussels, fish, andgeckos have in common? They allhave the ability to stick, or becomesticky. The most impressive memberof this group is the mussel. Musselsspend their lives permanentlyattached to rocks in the ocean. It’s astressful life—they’re constantlybombarded by harsh waves, yet theydon’t get washed away. Their secret?Well, the key to the mussel’s tenacityis a gluey secretion called byssus,which originates from glands in its“foot”. University of California atSanta Barbara researcher HerbertWaite discovered that these glandssecrete two materials: resinlike pro-

teins and hardening substances.When the two mix and contact water,they harden, forming a bond that isable to oppose thousand-poundforces. The hardening process iswhere all of the interesting chemistrycomes in.

Before the glue hardens, themolecules in the byssus are in theform of polymer chains that have sidegroups made of DOPA, or dihydrox-yphenylalanine.

Polymer chains are simply longchains of molecules that are cova-lently linked together. Why is DOPAimportant? Well, in its oxidized form,it is involved in the cross-linkingbetween the protein chains of the

http://chemistry.org/education/chemmatters.html8 ChemMatters, DECEMBER 2006

ChemSumer

Sticky Situations:The Wonders of Glue

By Linda Shiber

Mussel adhering to a sheet ofpolytetrafluoroethylene (Teflon).

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mussel glue, creating a meshwork that bindsthe mussel to its rock. Cross-linking is impor-tant for making the glue stick to itself and tothe surfaces to which it is adhering. However,the DOPA cross-link story doesn’t end here.Mussel glue contains a remarkably high con-centration of iron, and Jonathon Wilker at Pur-due University wanted to find out why.Research done by Wilker in 2004 revealed thatmussels use iron that is in the surroundingwater to join the byssus molecules togethervia their DOPA side chains, forming thiscross-linked framework. It turns out that eachiron atom can bind three DOPA side chains.

When the iron-DOPA linked moleculesare exposed to oxygen, the complex formsradicals. Radicals are extremely reactive sub-stances, and in this case, their reactivity isresponsible for internal cross-linking of theglue and for connecting the glue to surfaces.The end result of the process is a strong,waterproof adhesive that keeps mussels onthe rock of their choice for life.

Fish glueAlthough mussel glue is impressive for

its sheer strength, it only serves the purposesof the mussel. Other animal-derived glueshave been used by humans for serving theirown needs. Fish glue, as an example, is pre-pared by heating the skin or bones of certaintypes of fish in water. Extra-pure fish gluemay be manufactured from swim bladders.The protein-based substance was patented inthe 1750s, and it is still used today for varioustasks. Fish glue is special because it bondswell to leather and can be easily removed withhot water or steam (without damaging thebonded surfaces). These qualities make it agood candidate for, interestingly, pipe organrestoration and repair. Pipe organs rely onleather for the pneumatics, which control howmuch air is expelled from the pipes when akey is depressed. More specifically, when an

organist presses a key, an electric currenttravels through a cord to valves that open tospecific increments, controlling the air thatleaves the pipes and, in turn, the sound that’sproduced. Leather is used on the valve disks,the gaskets, and the pneumatics. Theseleather components inevitably wear out andrequire replacement. Fish glue is the choicewhen one must reaffix new leathers, becausewhen they deteriorate (after 50 years or so),the glue can be removed without causingdamage to the instrument.

Off to the glue factory …

Marine animals aren’t the only stickyorganisms, though. Glues are also made byboiling the hooves, hides, and bones of ani-mals such as horses. You may have heard thesaying that elderly horses are led off to theglue factory. There is some truth in it. Forinstance, hide glue was used in the past tomake bows, glue together ceramics, and isstill used today in woodworking. The glue ismade by heating hides and skins in an alkalinesolution containing lime (Ca(OH)2), whichsoftens and breaks downthe tissue, releasing colla-gen. Next, the hides are runthrough a water rinse toremove excess lime, andhydrochloric acid is addedto aid in the lime removal byneutralizing it. The resultingmaterial, called “stock”, getsheated for a specific amountof time, which allows furtherbreakdown of the collageninto a gluey material. As thishide glue cools, it attains agelatinous quality. When allwater has been evaporated,the hide glue becomes con-centrated in sheets orblocks. To use the hide glue,an appropriate amount isadded to hot water, melted,and then spread onto what-ever needs gluing.

We’ve got geckosclimbing the waals

Geckos climb on all kinds of surfaces,including ones that are completely vertical.Professor Autumn Keller and undergraduate

students at Lewis andClark College have discoveredhow the critters can defy gravity. Thekey to the gecko’s nimble footwork are mil-lions of tiny hairs, called setae, which arearranged on the pads of its feet. The setaeeach split into more tips called spatulae(amounting to figures in the billions), whichare microscopic. These miniscule hairs workto hold the gecko on a surface through amechanical approach, rather than by, say,secreting a gluey substance. The key to thegeckos “stickiness”, then, is something calledvan der Waals forces.

Van der Waals forces refer to three typesof attractive forces that can exist between neu-tral molecules: dipole-dipole forces, hydrogenbonding, and London dispersion forces. Thetype of van der Waals force employed by theagile gecko is London dispersion. These areweak electrodynamic forces between mole-cules caused by an instantaneous, temporarydipole of one atom inducing a similar tempo-rary dipole on an adjacent atom, causing theatoms to be attracted to one another.

All molecules experience van der Waalsforces, but the gecko’s secret is its surfacearea. Because there are so many setae andspatulae, the total area of the gecko’s foot incontact with the surface that it’s scaling canbe immense, so all the tiny attractions can addup to serious stickiness.

At any given moment, a molecule will have an unevendistribution of electron density. This creates temporary,

fleeting regions of partial positive and negative charges, or a dipole.

This induces an instantaneousdipole in a neighboringmolecule, giving rise to aweak electrostatic attractionbetween the molecules.

OO

FeO

OO

O

NH

NH

NH

N

OO

O

OH

O

O

NH

NH

NH

N

O

OOOH

O

O

NH

NHNH

N

O

OO

OH

OO

A.

B.

C. Induced dipoles occur throughout acollection of molecules. One dipoleinduces another, and another, andso on ... but only for a moment.

Van der Waals forces.

Each iron atom binds to three DOPA side chains.

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In addition to van der Waals forces, the gecko’s ability to stick is attributable togeometry. When a gecko runs, its footmoves in such a way that optimizes thecontact between its setae and the sur-face. The gecko actually pushes its footpads down and slides them forwardslightly, thereby initiating the stick-ing. To lift their feet back up, theangle at which the setae touch thesurface is increased, and the gecko“peels” each foot off the ground.

A glue by anyother name

Although hide glue might be news toyou, products like superglue and gorilla glueare probably much easier to recognize. Super-glue comes in small containers and packs awhole lot of stickiness. The molecule respon-sible for its adhesive qualities is cyanoacry-late, an acrylic resin. Cyanoacrylate wasdiscovered in the 1940s by a man namedHarry Coover who was working at the East-man Kodak company. Following his discoveryof this sticky substance, Eastman Kodakbegan looking into alternative uses for thematerial. The key to cyanoacrylate glue wasthat it stuck to skin. Hence, research was doneto see if it could be used medically to hold thetissue surrounding surgical incisions together.It could and it did. In fact, during the VietnamWar, a cyanoacrylate glue spray was used onbattle wounds as a fast way to stop bleedinguntil the injured person was transported to amedical facility.

So how does cyanoacrylate work itsadhesive magic in products like Superglue?Well, in its liquid state, Superglue’s mainingredient is the monomer methyl-2-cyano-acrylate. Exposure to water (or, the traceamount of hydroxide ion present in water)causes the monomers to undergo a polymer-

ization reaction in which they form longchains that can connect two surfacestogether.

Because trace amounts of moisture existon most surfaces, Superglue cures quicklyand without much coaxing. The reason thatSuperglue doesn’t stick to the walls of its

package is because an acidic stabilizerhas been added. This stabilizer pre-

vents the formation of polymerchains but is overridden

in the presence of thethin layer of water

molecules thatcoats most sur-faces whereverthere is moderatehumidity.

Is there anyway to reverse the

strong, waterproofbond that Superglue

makes? There are some factors thatmay weaken its adhesiveness. For instance,heating glued objects to a temperature greaterthan 180 °F, or exposing it to temperaturesless than 30 °F will soften the glue or cause itto become brittle. Acetone, a substance foundin nail polish removers, can also soften thebond by partially dissolving the polymerchains, making it easier for them to slip pasteach other.

Primates andpolyurethane

Another type of human-made glue thatmay be familiar to you is Gorilla Glue. GorillaGlue is used in home repairs and woodworkingand is lauded for its waterproof bond. In con-trast to Superglue, Gorilla Glue doesn’t drywithin seconds. Rather, it allows the personusing it a 20-minute window in which surfacesmay be shifted and adjusted to glueable perfec-tion. What’s the key to this bond? The answeris polyurethane polymers. A polyurethane poly-mer is a chain of molecules attached to oneanother via urethane links. The central reactionresponsible for chain formation is between twotypes of monomers: a polyol (polyethylene gly-col or polyester polyol) and a diisocyanate

(either aromatic or aliphatic).Depending on the type of

monomers and/or catalysts used,polyurethanes have widely differentproperties. Although the substance isused as a glue, through variation of

the polymerizing reagents and through vari-ous additives, it may acquire properties thatallow it to act as a varnish or a foam. Forexample, using an aromatic diisocyanatemonomer would create a substance with dif-fering mechanical properties as opposed tousing a linear monomer. The same variation is

seen with the polyol used; a polyethylene gly-col monomer produces a softer, more flexiblepolyurethane than a polyester polyol might.

The sticky-icky lowdown

Now that we’ve profiled how differentkinds of glue form bonds, the next logicalquestion is how do glues interact with the sur-faces they’re gluing? How does a glob of glueconvince two objects to stick to it and to eachother? There are several ways this can occur.The first way is pretty much common sense.Glues work mechanically by invading thepores and cracks in the two surfaces, increas-ing the area that becomes sticky. Sometimes,the effectiveness of glue can be increased bymaking the surfaces rougher. This providesthe glue with plenty of crannies it can diffuseinto and occupy.

Another major way that glues work is bytaking advantage of electrostatic forces pre-sent on the surfaces of the objects beingglued. Different objects contain moleculeswith varying dipole moments, which mayattract them to one another. An adhesiveforce is created when electrons are trans-ferred from one surface to another, creatingpositive and negative charges, which areattracted to one another.

It’s clear that there’s a lot more to gluethan its sentimental role as a childhood snack.Animals make it, people make it, and it holdstogether so many of the items we rely uponevery day. Look around. Glues are every-where, from the natural world to the chem-istry lab. It would be virtually impossible toseparate our lives from them. Not that we’dwant to, of course. The bottom line, then, (andpardon the pun) is that we’re stuck on glue.

Period.

REFERENCESBurdick, A. Biochemists Turn to Mussels for

a Real Bonding Experience. Discover,2005, 24.

Cobb, C. and M. Fetterolf. The AmazingScience of Familiar Things. New York:Prometheus Books, 2005.

Goho, A. Marine Superglue: Mussels GetStickiness From Iron in Seawater, ScienceNews Online, 2004,165.

Additional references can be found in theTeacher’s Guide.

Linda Shiber is a freelance writer living inLouisville, KY. She is working on a medical degreeand lives with her dog, Ralph.

http://chemistry.org/education/chemmatters.html10 ChemMatters, DECEMBER 2006

H H H

H

CN O

O O

CN

C O CH2

CH3 Polycyanoacrylate

CH2

CN n

O O

C CH3

O C

CH3

O

Setae of a gecko foot.

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uring World War I, Ger-man submarines werefeared in the waters of theNorth Atlantic and in theBaltic Sea between the

coasts of Sweden and Finland. Many com-mercial freighters were sunk in the frigidwaters because they were suspected of car-rying war supplies or troops. The Germanattack sub, U22, located the two-mastedSwedish schooner Jonkoping 28 miles fromthe Finnish coast. There was little doubt as tothe outcome. The fateful morning for theJonkoping was November 3, 1916. Her rest-ing place for the next 82 years would be 197feet below the surface in the icy cold watersof the Baltic Sea.

Swedish divers Claes Bergvall and PeterLindberg located the almost perfectly pre-served wreck in 1997. The divers found therigging destroyed, but there was only a smallhole in the hull. The wreck was of great inter-est because of its cargo … she was loadedwith 10,000 gallons of cognac, 17 barrels ofBurgundy wine, and 3000 bottles of Heidsieck& Co. Monopole 1907 “Gout Americain”champagne, intended for officers in the Rus-sian army. (*Note of interest … the 1907 Hei-

dsieck was also the wine on the H.M.S.Titanic’s maiden voyage.)

In July, 1998, salvage operations beganto remove the precious cargo from the oceanfloor. Because of the exceptional condition ofthe wreck, salvagers expected the best …recovery of what would now be consideredsome of the rarest alcoholic beverages onearth! From the cargo, 21 barrels of cognacwere salvaged, as well as 2500 bottles of the1907 champagne. The cognac was discoveredto contain salty seawater and was not suitablefor drinking, but the champagne proved to bea real “treasure.” The champagne was so wellpreserved because it was shipped in strongwooden cases, which prevented most of thebottles from breaking while the Jonkopingsank. And for 82 years, the bottles werestored in the complete darkness, 197 feetbelow sea level at a constant temperature of 3 °C (about 37 °F). At this depth, water pres-sure (every 33 feet in depth provides oneadditional atmosphere of pressure) helped tokeep the corks in place and the effervescenceinside the bottles. The Baltic is a young sea inevolutionary terms and the absence of wood-destroying worms or parasites further helpedto preserve the champagne.

But the pressure at these depths alsoprovided salvagers with a challenge—how toget the bottles to the surface without “blowingtheir corks.” Two gas laws come into playwhen bringing “carbonated” beverages froman area of high pressure to an area of lowpressure. The first, Henry’s law, states that thesolubility of a dissolved gas decreases whenthe partial pressure above the solution isdecreased. In a mixture of gases, the partialpressure of a gas is the pressure it wouldexert if it alone occupied the same volume atthe same temperature. The second law to con-

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Bärgningen

Stockholm

Lyft Säckarna och kranen lyfter Jönköping från 64 meters djup och transporterar henne till grundare vatten.

Jönköping ligger på 64 meters djup 30 km väster om Raumo


High gas pressureLow gas pressure

Gas

Gas

Liquid

Liquid

Henry’s Law

In accordance with Henry’s law, as the pressureon the corks decreases, more CO2 will come outof solution.

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sider is Boyle’s law, which states that at aconstant temperature, as pressure decreases,the volume of the gas bubbles will increase.(See sidebar “Scuba and the gas laws”, in“SCUBA: The Chemistry of an Adventure”, pp. 8-9, ChemMatters, Feb. 2001) Together,these two gas laws could result in the bottles“blowing their corks” with the ultimate loss oftheir precious contents.

Eighty-two years in the Baltic Sea hadcorroded away the wires that the bottlers hadused to secure the corks in the bottles. Divershad to first engineer a way to keep the corksin place prior to bringing them to the surfacewhere the pressure is drastically reduced. Awire screen was eventually secured over thecork of each bottle to keep the precious “bub-bly” in the bottles. Once this obstacle wasovercome, the salvage operation could begin.

Chemistry of champagne

Champagne is named after the region innorthern France where the “bubbly” wine firstgained its reputation. Champagne from thisregion is made from three varieties of grapes:Pinot Noir, Pinot Meunier, and Chardonnay.To start, the grapes are pressed, and the juiceis separated from seeds and skins before theyhave had time to impart any color. This juicethen undergoes its first fermentation, usuallyin large containers. During this primary fer-mentation, the simple sugars (glucose andfructose) present in the grapes are convertedto ethanol (CH3CH2OH, also called ethyl alco-hol) and CO2. A wine master will then decidehow the three varieties of grapes will beblended to achieve the desired still wine. Stillwine is wine with no fizz.

Now the process of making the “fizz”begins. After the still wine has beenblended, it is bottled in a thick glass bottleto withstand the pressure created by car-bon dioxide bubbles that form during thesecond fermentation process. A dose ofsugar solution and Saccharomyces cere-visiae, or yeast (the mixture is called

liqueur de triage) is added to the still wine,and the bottle is capped. As the sugar inthe wine ferments, more ethanol and car-bon dioxide are produced. The carbon diox-ide gas dissolves in the wine under theincreased pressure (~5–6 atmospheres)and the “fizz” is created.

This process must be kept under anaero-bic conditions to prevent oxygen from react-ing with the ethanol, turning it to acetic acid.Oxygen could also react with the sugardirectly, producing only CO2 and water.

Effervescence:understandingbubbles

When one thinks about champagne, aglass of bubbling beverage usually comes tomind. But why do bubbles form in cham-pagne? The bubbles form as a result of previ-ously dissolved carbon dioxide gas escapingfrom solution. Carbon dioxide is a gas at roomconditions with only minimal solubility inwater. Reduction in pressure or addition of

heat reduces its solubility further.After the cork comes out, the pres-sure above the liquid is reduced,and the carbon dioxide starts itsjourney to the surface! But in orderfor the CO2 to come out of solu-tion, it first needs a place wheremicroscopic vapor bubbles cancongregate until they form a buoy-

ant bubble. Called a nucleation site, it may bean imperfection in the glass, some dust or anyother deposit that prompt the CO2 to make aphase transfer or to come out of solution.

Once the bubble develops enough buoy-ancy, it detaches from the nucleation site andcontinues to grow as it rises. Bubbles grow asthey ascend in the glass or bottle because car-bon dioxide diffuses from the liquid into thegas bubble. The higher pressure of the gasdissolved in the liquid compared with that


C6H12O6 + yeast ! 2 CH3CH2OH + 2 CO2

+ yeast!

0 1 0 0 k m

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7 m

Beginning in November 1997 the work began to lift schooner Jonkoping.

The value of the cargo was estimated to be 100–500 million kronor which is about $16–$84 million.

On 28th October 1916 schooner Jonkoping left Gaevle with champagne and cognac for the Russian czar’s army. The cargo also included materials for a railway and that was the reason why the captain of the German fleet sank the vessel.

Jönköping cargo

2 0 m

20

m

Champagne produced in 1907, 44 boxes, 100 bottles each = 3300 liters

Cognac67 barrels, 40, 200 liter

Hole:1 x 0.8 meters made by the torpedo

Two crew members lived in the back cabin.

Stockholm

Lyft Säckarna och kranen lyfter Jönköping från 64 meters djup och transporterar henne till grundare vatten.

Built: 1895 in Sjötorp by Vänern Lake

Type: Galeas (Skonare)

Crew: 5 men

Engine: 16 hp

Capacity: 90 tons

Weight to be lifted: 100 tons

Facts about the vessel

Jönköping ligger på 64 meters djup 30 km väster om Raumo

jo h a n t a n d e rs s o n

Wreck with champagne being lifted

Wine 17 barrels, 340 liters each = 5780 liters

Three crewmen slept in the front cabin.

Stokholm

Helsingfors

Jonkoping was lying 64 m deep and 30 kmwest of Raumo.

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The formation of CO2 and ethanol via the fermentation of sugarusing yeast. The reaction is depicted using ball-and-stickmodels (top) and molecular formulas (bottom).

Typical photograph of a regular bubble train. Thenucleation site is at the very bottom, possibly atiny imperfection in the glass.

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inside the bubble determines how big thebubble will ultimately become. This bubblingphenomenon is known as effervescence.

Champagne makers would like to betterunderstand their bubbles and learn to controlthem because people (especially in France)make a connection between the quality of thechampagne and the smallness of the bubbles.Recent scientific studies of champagne haverevealed some interesting information. Thedata have shown that different concentrationsof protein molecules in the champagne affectthe bubble chemistry (and physics). Risingbubbles often pick up suspended or dissolvedmaterials that stick to bubble surfaces.

Adsorbed molecules stiffen a bubble by form-ing a molecular layer on its surface. Accordingto fluid mechanics, a stiffer sphere movingthrough a liquid runs into more resistance, ordrag, than one with a more flexible skin.These adsorbed molecules tend to slow bub-bles down. In the absence of other influences,such as a nearby glass wall, the most rigidbubbles show the greatest drag. Champagnehas little protein to form the more rigid bub-bles found in other beverages (like soda, forexample) and therefore grow too quickly toproduce much drag. As a result, small bub-bles in champagne rise to the surface rapidly… a trait that characterizes “bubbly.”

Back to makingchampagne

The wine is now stored in a cool (11 °C)dark cellar, sometimes for several years, dur-ing which time the dead yeast cells called leesgive flavor to the wine. Occasionally, the bot-tles, now stored upside down, will be turnedand tapped to release the dead yeast cells,which will fall into the neck of the bottle. Thispart of the process is called remuage. Nextcomes degorgement; the neck of the bottle isfrozen, and the frozen sediment of dead yeastcells is removed. The remaining solution istopped off with wine and sealed with cork,wire, and foil and voila … champagne! Theentire process takes at least 1 year for nonvin-tage champagnes, while vintage champagnesrequire three years or more. Quality vintagechampagnes can command a high price,sometimes even hundreds of dollars. And rarevintage wines have commanded thousands ofdollars per bottle at auction. In 1985, MalcolmForbes paid $156,450 for a single bottle ofThomas Jefferson’s Lafite Rothschild 1787!

Back to our storyOver 2000 bottles of rare, vintage Heid-

sieck & Co. Monopole 1907 “Gout Americain”champagne were eventually salvaged from theJonkoping. Chemical analysis and tastingrevealed that the bottles contained exceptionalchampagne with no negative effects from thelong stay on the floor of the Baltic Sea. InOctober 1998, the famous auction house,Christie’s, sold 24 bottles at a staggering priceof about $3000 per bottle. (This was still farbelow what Christie’s had estimated …$8000/bottle.) Much of the champagne is nowin storage and will eventually be sold. Currentestimates place the value of the cargo atbetween $8 and 10 million.

REFERENCESLemonick, M., Stradivari’s Secret—

Biochemist Jospeh Nagyvary's Researchon Violin-Making, Discover, July, 2000.

Liger-Belair, G., Effervescence in a Glass ofChampagne: A Bubble Story, EurophysicsNews, 2002, 33.

Weiss, P., The Physics of Fizz, ScienceNews, May 6, 2000.

Additional references can be found in theTeacher’s Guide for this issue.

Tim Graham teaches chemistry at Roosevellt HighSchool in Wyandottte, MI. His most recent articlesof ChemMatters include “Poisoned” and “TheSecrets of the Samurai Sword Revealed” whichboth appeared in December 2005.


Other Treasures From the DeepSunken treasure can also be found in the Great Lakes of North America. No gold doubloons

or precious jewels from sunken pirate ships, but treasure nonetheless. The Great Lakes are cur-rently being mined for valuable submerged lumber! Sonar equipment is being used to locate andsalvage logs that were lost between the mid-1800s and early 1900s while the wood was en routeto lumber mills.

The dense virgin forests in which this wood grew no longer exist. This lumber, preserved inthe cold waters of the Great Lakes, is unlike anything that can be found today. The density andgrain quality of the wood are extremely high, with the added benefit that it comes from tree typessuch as red birch, red oak, hard maple, beech, and white pine that may no longer be available towoodworkers. Its long stay under water has done much to change the wood’s chemistry, which,in turn, has added to its value as “recovered treasure”.

When wood is submerged in water, anaerobic bacteria eat a cell wall material called hemicellulose. Hemicellulose is a natural polymer with a random, amorphous structure. Themonomers that are joined to make this polymer include glucose, mannose, arabinose, xylose, andglucuronic acid.

Once the hemicellulose has been digested, it is theorized that minerals seep into the cells,crystallize, and ultimately enrich the quality of the wood. Salvaged lumber is finding new life in themaking of fine furniture and, even more interesting, musical instruments.

Joseph Nagyvary (retiredprofessor of biochemistry, TexasA&M, College Station, TX) hasbeen building violins recently

from wood found at the bot-tom of Lake Superior. Longinterested in the superior

quality of the legendaryStradivarius violin, Nagy-

vary theorized thatStradivarius mayhave soaked thewood he used for

making violins, sometimes for months or even years, in mineral-rich water. Oncedried, this wood took on outstanding qualities found only in the now-famous vio-lins. Salvaged lumber is becoming a prize for woodworkers around the world. Andthose who are selling salvaged lumber are certainly finding it to be like “treasure”,every bit as valuable as gold. Boards cut from this rare lumber are selling for hun-

dreds and even thousands of U.S. dollars! Not bad for an old piece of wet wood.

The structure of hemicelllulose.

COOH

CH3O

HO

HO

HO HO

HO HO

HO

OH OH

OH OH

OH

OH

OH

O O

O

O O

O

O O

O O O

O

O

O O O

O

O CH2OH OH

AcO AcO

HOCH2

CH3

OAc

n

e have all used a ther-mometer—to check for a fever, record data dur-ing a chemistry lab, or tohelp us decide how to

dress before leaving for school in the morn-ing. But have you ever thought about how athermometer works? And when you measuretemperature, just what exactly are you measuring?

The prefix thermo- refers to heat. Ther-modynamics is the study of heat. A thermoseither keeps heat in or out. You wear thermalunderwear to prevent body heat from escap-ing. Despite its name, however, a thermome-ter does not actually record heat, but rathertemperature. Temperature and heat are tworadically different concepts.

Temperature is a measure of the averagekinetic energy of the molecules within a sub-stance. When you record the temperature ofsomething, you are making a statement abouthow fast the molecules are moving. When youare waiting for a bus in the morning in themiddle of January, instead of saying, “Boy, itscold out here this morning,” it would be moreaccurate to say, “Boy, the molecules in the airare moving quite slow this morning!”

Heat vs. temperature

Heat is a little trickier to define. Heatrefers to the movement of energy from asubstance of high temperature to one of lowtemperature. Heat always refers to energy intransit. A substance can have a high temper-ature, but little heat available to transfer. Adrop of boiling water contains less actualheat than a bathtub full of water at a lowertemperature. Temperature is a measure ofonly the average kinetic energy of molecules,but because heat depends on the totalenergy, there is not a simple, universal rela-tion between the two.

Here’s an everyday example that helpsto illustrate the difference between heat andtemperature. Consider ice: when you cool adrink using ice, a lot of heat flows from thedrink into the ice (so the drink’s temperaturefalls). But the temperature of the ice does notrise, it stays at 0 °C—the heat goes intobreaking the interactions between water mol-ecules to melt the ice (at 0°) to form water(still at 0°). Ice and water at 0° have thesame temperature but very different amountsof heat.

Temperature scalesIn the United States, most thermometers

for everyday use are calibrated in degreesFahrenheit. Most of the rest of the world mea-sures temperature in degrees Celsius. At onepoint during the 18th century, there werenearly 35 different temperature scales in use!Many scientists felt the need to devise a uni-form temperature scale that would meet wide-spread acceptance.

One temperature scale that met withsome success was the Romer scale, whichwas first used in 1701. This temperature scalewas invented by Ole Christensen Romer, aDanish astronomer whose biggest claim tofame was measuring the speed of light in1676. His temperature scale set the boilingpoint of water at 60° and the freezing point at7.5°. The lowest temperature you couldachieve with a mixture of salt and ice was 0°.Because most people from that time periodwere not too concerned about the temperatureof ice and salt, this scale was destined for thedustbin of history.

Daniel Gabriel Fahrenheit, a Germanphysicist, published an alternate scale in1724. Borrowing from the work of Romer,


WBy Brian Rohrig

You are feeling sick.You call the doctor andshe wants to know theaverage kinetic energy of your body’s molecules.What will you do?

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he set 0 °F as the lowest temperature thatcould be achieved with a mixture of salt, ice,and ammonium chloride. (It is unclearwhether Romer also used ammonium chloridein his experiments, as many of his recordswere destroyed in a fire.) Fahrenheit set thefreezing point of water at 32° and the bodytemperature of a person at 96°, which hedetermined by measuring the temperatureunder his wife’s armpit. Each degree of hisscale corresponded to one ten-thousandth theinitial volume of mercury used in his ther-mometer. To this day, there is considerablecontroversy as to how Fahrenheit actuallyarrived at his temperature scale. He never didreveal exactly how he arrived at the referencepoints for his thermometer, as he did not wantothers to construct and sell the thermometershe had spent much of his life perfecting.

His scale met widespread acceptancebecause everyone could relate to it, since 0 °Fand 100 °F were the lowest and highest tem-peratures typically experienced on any type ofregular basis in Western Europe. If the tem-perature rose above 100°, you knew it wasreally hot. If the temperature dipped below 0°,you knew it was quite cold. Whether thesepoints were intentionally chosen to representthese extremes or just happened to work outthis way is still being debated today. Thebiggest problem with this scale was the freez-ing and boiling points of water were set at 32ºand 212°, not exactly round numbers. Thiswas an issue not so much with the generalpublic, but rather with scientists, who tend toobsess over such things. However, othershave postulated that placing 180 degreesbetween the freezing and boiling points ofwater was not arbitrary but quite rational, asthis number represents the number ofdegrees in half a circle.

To counter this problem, Swedishastronomer Anders Celsius came up withanother scale in 1742, settingthe freezing and boiling pointsof water at 0° and 100°, with100 divisions in between.Hence, it was termed theCentigrade scale, since theprefix centi- represents one-hundredth. Celsius had ini-tially set the freezing point ofwater at 100° and the boilingpoint at 0°. This was laterreversed after his death. Mostcountries that have adoptedthe metric system of mea-

surement usethis temperaturescale, as it isconvenientlybroken downinto units of 10.In 1948, theCentigrade scalewas officiallydesignated theCelsius scale,although somepeople still use the outdated term.

The most scientific scale in use today isthe Kelvin, or absolute, temperature scale. Itwas devised by British scientist WilliamThomson (Lord Kelvin), in 1848. Becausetemperature is a measure of molecular

motion, it only makes sensethat the zero point of your scaleshould be the point where mol-ecular motion stops. That isexactly what the Kelvin scaleaccomplishes. 0 Kelvin (K) isthe point at which all moleculesstop moving. 0 K is known asabsolute zero, which has neveractually been reached. In 2003at MIT, scientists came veryclose to reaching absolute zero,obtaining a frosty temperatureof 4.5 ! 10-9 K.

The Kelvin scale is primarily used in sci-ence, and temperature must be expressed inKelvin when solving many equations involv-ing temperature, such as the gas laws. But ittends to be too cumbersome for everydayuse, since the freezing point of water is 273 Kand the boiling point is 373 K.

Types of thermometersEarly thermometers

The first thermometer in modern timeswas a crude water thermometer believed tohave been invented by Galileo Galilei in 1593.In 1611, Sanctorius Sanctorius, a colleague ofGalileo’s, numerically calibrated the ther-mometer. Many of these first thermometersused wine, as its alcohol content prevented itfrom freezing and its red color made it easy toread. However, these first thermometers werevery sensitive to air pressure, and functionedas much as a barometer as they did as a ther-mometer. So eventually, all thermometerswere constructed of a sealed glass tube thathad all the air removed. Becausethese vacuum tubeswere shut

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off from the outside atmosphere, changes inair pressure would not affect the temperaturereading. In 1709, Fahrenheit invented the alco-hol thermometer, and in 1714, he invented thefirst mercury thermometer. All thermometerswork according to the same basic principle:objects expand when heated and contractwhen cooled.

Bulb thermometersThe most common thermometer is the

bulb thermometer, which comprises a largebulb filled with a liquid and a narrow glasstube through which the liquid rises. All liquidsexpand when heated and contract whencooled (with the exception of H2O near itsfreezing point; ice-cold H2O at 0 °C contractsuntil 4 °C where it expands like other materi-als), which explains why the liquid within athermometer rises as the temperatureincreases and falls when it decreases. Mer-cury was the liquid of choice for many years,because it expands and contracts at a veryconstant rate, making mercury thermometersvery accurate. However, because of concernsabout mercury toxicity, mercury has oftenbeen replaced with alcohol that is colored red.Mercury has a silver color. It freezes at –39 °C, so it cannot be used if temperaturesget colder than this.

Bimetallic strip thermometers

Another very commontype of thermometer is thebimetallic strip ther-mometer. This ther-mometer comprisestwo different metals,such as copper andiron, which arewelded together. Eachof the metals used hasa different coefficient oflinear expansion, or to put itsimply, these metals expand atdifferent rates. Connected tothis bimetallic strip is apointer, which points to the correct tempera-ture on the face of the thermometer. Becausethese metals expand at different rates, whenheated, the welded strip of metal will bend.When cooled, it will bend in the oppositedirection. A variation of the bimetallic stripthermometer is the thermostat used in homesand automobile engines. These thermostats

are made of a thin bimetallic strip, which isfashioned into a coil, making it more sensitiveto minor temperature fluctuations.

Infrared thermometers

A fascinating thermometer is theinfrared thermometer. This handheld device isused by simply pushing a button as you pointit toward an object. A digital readout tells youthe temperature. All objects above absolutezero are emittinginfrared radiation (IR)—an invisible (tohuman eyes) form ofelectromagnetic energy.The infrared radiationwe emit is commonlyknown as body heat.The infrared thermome-ter has a lens thatfocuses the infrared energy into a detector,which measures the IR intensity and convertsthat reading to temperature. Infrared ther-mometers have a wide variety of applications.They are used by firefighters to detect hotspots in buildings and in restaurants toensure that served food is still warm. Infraredthermometers are also used for determiningthe temperature of a human body, automobileengines, swimming pools, hot tubs, or when-ever a quick surface temperature is needed.

Pop upsYou are cooking

that Thanksgivingturkey, and youwant to makesure that theinside of theturkey is com-pletely done. To

ensure that youare not feasting on

undercooked bird,you can use an inge-nious device knownas the pop-up turkey

timer. This instrument is simplystuck into the turkey, and whenthe turkey is done, a red indicatorpops up (A). The little red indica-tor is spring loaded (B) and isheld in place by a blob of solidmetal (C). When this metal reaches a temper-ature of 85 °C, which is the temperature of a

fully cooked turkey, it melts, causing the redindicator to pop up.

This technology is similar to that used insprinklers found on the ceilings of manybuildings, which actually served as the inspi-ration for the pop-up turkey timers. When acertain temperature is reached, a metal com-ponent within these sprinklers melts, activat-ing the sprinkler. By mixing together differentmetals, a particular alloy can be created with adesirable melting point. Pop-up timers can bepurchased for a wide variety of different typesof meat, from ham to hens. You can even buya pop-up timer for steak, which pops up inincrements indicating rare to well done.

And now for some-thing completely different…

Perhaps the mostunusual thermometerever invented is theGalileo thermometer,based on a similardevice invented byGalileo. This instrumentdoes not look like athermometer at all, as itis composed of severalglass spheres contain-ing different coloredliquids that are sus-pended in a cylindrical


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column of a clear liquid. Attached to each ofthe colored spheres is a little dangling metaltag with an engraved temperature. The tem-perature is determined by reading the tag onthe lowest floating sphere. As the temperaturerises, the spheres will begin to fall one byone. When the temperature falls, the sphereswill then rise one by one.

The liquid within each glass sphere iscomposed of either colored water or alcohol.Each of the spheres is of a slightly differentmass, and thus a slightly different density,since the volume of each sphere is the same.Each sphere differs in mass by about 0.006grams. This difference is accomplished bymaking each tag a slightly different mass. The clear liquid surrounding the spheres is an inert hydrocarbon-based oil, similar tomineral oil. When this liquid is heated, itexpands, becoming less dense. Less denseliquids exert a lesser buoyant force, so themost dense sphere will then sink. If the tem-perature continues to rise, the molecules ofthe surrounding liquid will continue to spreadapart from one another, causing morespheres to fall. As the liquid cools, its mole-cules come closer together, exerting a greaterbuoyant force, causing the spheres to rise.The spheres themselves do not expand orcontract nearly as much as the surroundingliquid when heated or cooled, since they arecomposed of glass, which hardly expands atall when heated.

Even though it looks nothing like a con-ventional thermometer, the Galileo thermome-ter still functions according to the same basicprinciple as most other thermometers: sub-stances expand when heated and contractwhen cooled.

What’s the future forthermometers?

Technology has come a long way sinceGalileo’s day, but his thermometer to this dayhas a futuristic look to it. Another futuristicthermometer that is available today is theCorTemp thermometer. Developed by Dr.Leonard Keilson of the Applied Physics Labo-ratory of the Johns Hopkins University in con-junction with NASA, the CorTempthermometer is swallowed, allowing accuratetemperature readings while it travels through,or is stationed at some particular spot in thebody. The probe is enclosed in a small pill thatis taken internally, while the temperature read-

ings are recorded on a device that is moni-tored externally.

No matter what device you use to takeyour temperature when you have a fever, nonewill make you feel better. But in this techno-

logically advanced world today, your choice ofthermometer might bring you a bit of wel-comed distraction while measuring the aver-age kinetic energy of your body’s molecules.


REFERENCESMaddox, B. Nightmare of divided loyalties. Discover. June 2006, pp 26–27.Shactman, T. Absolute Zero and the Conquest of Cold. Houghton Mifflin Company: New York,

1999.

INTERNET REFERENCESFahrenheithttp://en.wikipedia.org/wiki/FahrenheitHow Pop-Up Turkey Timers Workhttp://home.howstuffworks.com/pop-up-timer.htm/printableHow Thermometers Workhttp://home.howstuffworks.com/therm.htm/printableThe History Behind the Thermometerhttp://inventors.about.com/library/inventors/blthermometer.htm

Brian Rohrig teaches at Jonathan Alder High School in Plain City, OH. His most recent ChemMatters article,“Glass: More Than Meets the Eye”, appeared in the October 2006 issue.

The CorTemp system can measure and record the bodytemperature and/or heart rate of many athletes on the field duringpractices or competition. Once the probe is inside the gastro-intestinal tract, a crystal sensor vibrates at a frequency relative tothe temperature of the body tissues surrounding it. These data arethen transmitted harmlessly through the body to the monitor.

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The emperorNapoleon Bonaparte was known

for lots of things. He was a soldier, ageneral who conquered most ofEurope. He was emperor of France. Hehad a dessert named after him. How-ever, not everyone knows that the littleemperor had a thing for science. Itmay seem odd that even though hewas engaged in a war with England,Napoleon would allow the biggest starof British science to visit France tomix and mingle with the top Frenchscientists of the day. Nevertheless,that’s just what happened in October1813. Napoleon granted Sir HumphryDavy permission to spend severalweeks in France, even though theirtwo countries were in the middle of awar. There wasn’t much Napoleonloved more than war, but it seemseven war could take a back seat to hislove of science now and then. Littledid the emperor realize how muchtrouble would be stirred up by his graciousness.

The showmanHumphry Davy was born in a far

corner of England in a town called Pen-

zance. His familywasn’t wealthy, andDavy never had alot of formal educa-tion. He educatedhimself through hisown hard work andbecame the mostimportant chemist

in Britain. A man of many interests,Davy also wrote poetry. Samuel TaylorColeridge, William Wordsworth, andLord Byron were his good friends. Heloved hunting and fishing as well.

Davy first made a big splash inscience when he discovered the effectsof nitrous oxide, or laughing gas, whenhe was only 21 years old. Later, he dis-covered two new elements, sodium andpotassium, with the help of electricityfrom a new-fangled battery. He thenwent on and discovered four more ele-ments: magnesium, calcium, stron-tium, and barium.

Davy wasn’t just a researcher. Hewas also an entertainer. In those days,lots of people paid money to see sci-ence demonstrations. Davy wowedaudiences with the wonders of chem-istry and electricity. His charm andcharisma made him the most famous

scientific showman in Britain, andthere was nothing Davy loved morethan fame.

He didn’t mind money, either. In1813, Davy had plenty of that too, ashe married a wealthy widow namedJane Apreece, not long before he leftfor France. Humphry and Jane wouldmake a sort of honeymoon out of thetrip. Not many brides dream of spend-ing their honeymoons in the middle ofinternational scientific spats, but that’swhat awaited the new Mrs. Davy as thecouple headed south across the Eng-lish Channel.

The protégé Joseph-Louis Gay-Lussac hailed

from a part of central France calledLimousin. He was the exact opposite ofHumphry Davy in many ways. WhileDavy had taught himself everything heknew about science, Gay-Lussac hadattended the best schools for math andscience in France. While Davy wasflamboyant and charismatic, Gay-Lus-sac was calm and reserved. Davy lovedleisure, spending lots of time on hismany hobbies, while Gay-Lussacseemed to have been wholly devoted tohis science. Spending time with hiswife Josephine and their children wasabout his only escape from his work.

Gay-Lussac was patient and care-ful in the lab. A very by-the-book kindof guy, he was very cautious aboutdrawing any conclusions from hisexperiments. When he did draw con-clusions, he always had lots of experi-mental results to back them up. Thisapproach paid off when Gay-Lussacdiscovered Charles’ law (V1 / T1 = V2 / T2) and when he discov-ered that gases always reacted in sim-ple whole number ratios by volume.

Gay-Lussac and Davy were oftenrivals. After Davy discovered sodiumand potassium, the two scientistscompeted to learn as much as possi-ble about the two new metals. Eachoften thought the other was horning inon his scientific turf as they raced tomake new discoveries. When Davyshowed up in Paris in October 1813,perhaps it was only a matter of timebefore they’d end up competingagainst each other again.


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Gay-Lussac was a friend of an olderchemist by the name of Claude-Louis Berthol-let. Berthollet had trained Gay-Lussac to workin the lab, and Gay-Lussac was like a son toBerthollet. Berthollet had also brought Gay-Lussac into a circle of scientists who oftenmet at Berthollet's house in the village ofArcueil (pronounced “Ar-koy”), just outsideParis. This group was called the Society ofArcueil, and it included some of France’s lead-ing scientists. Members could use Berthollet’slaboratory and were more likely to get theirpapers published in the scientific journalsBerthollet published. It definitely paid to be afriend of Berthollet.

Berthollet had sent Gay-Lussac on one ofhis first adventures as a scientist. In 1804,Berthollet asked Gay-Lussac to carry out avery dangerous experiment. Wanting to mea-sure the earth’s magnetic field at high alti-tudes, he rode a hydrogen balloon to a heightof over 23,000 feet above sea level. This set aworld record that stood for almost 50 years.

Nine years later, Humphry Davy was mak-ing a stir by visiting France during the middle ofa war. In November 1813, while Davy was inParis, Gay-Lussac was given an assignment bythe National Institute, France’s leading scientificorganization. Two not-so-well-known chemists,Nicolas Clément and Charles Bernard Des-ormes had reported that a strange new sub-stance had been discovered in seaweed. Thesubstance formed small black crystals andcould produce a purple vapor. Even though itwas a solid, it seemed similar to chlorine insome ways. Clément and Desormes had car-ried out some experiments on the new sub-stance and reported them to the Institute. Theyclaimed, among other things, that the sub-stance formed an acid when it came into con-tact with hydrogen. Gay-Lussac was assignedto review their experiments and repeat them tomake sure the results were correct. He set towork, studying the substance carefully andthoroughly. While studying it, he gave the sub-stance a new name. He called it iode, from anancient Greek word for “purple.” Little did heknow that Davy had already been tipped off.

The outsiderPerhaps more brilliant than any of the

scientists in the Society of Arcueil was aphysicist and mathematician by the name ofAndré-Marie Ampère. He had been a childprodigy and made important discoveriesabout electricity. He was a scientific genius,but he could be awkward in social situations.He never cozied up with Berthollet and theSociety of Arcueil the way Gay-Lussac had.

Maybe if Ampere had been tighter withthe Society of Arcueil, they might have toldhim to be more careful about what he toldDavy. At any rate, some time before Clémentand Desormes announced their new sub-stance to the National Institute, they gave asample of the substance to Ampère. Six daysbefore the announcement, Ampère, Clément,and Desormes paid a visit to Humphry Davy.Ampère brought with him a sample of thesubstance to show the famous visitor. It's atthis point that a misunderstanding took place.Ampère probably thought he was showingDavy the new substance as a courtesy to avisitor. On the other hand, Davy claimed theFrench scientists were asking him to investi-gate the substance—as if French chemistsweren’t smart enough to do that themselves.(Davy was known for his big ego.) Davy hadbrought a trunk of scientific glassware andinstruments with him from Britain. Now, hehad a reason to use it and got to work. Hebegan to study the new iode, and gave it it’sEnglish name, iodine.

The raceOnce again, Davy and Gay-Lussac were

in competition. Gay-Lussac thought Davy wasbeing a bad guest by nosing in on a Frenchdiscovery right on their home territory. Bothprobably couldn’t forget that their two coun-tries were at war, and the rivalry took on anationalistic tone. Davy was researching forKing and Country, while Gay-Lussac wasresearching for the glory of France. As theycarried out extensive investigations of iode,neither Davy nor Gay-Lussac seemed to caremuch that they were both technically nosingin on Clement and Desormes, who had firstbrought iodine to everyone’s attention in thefirst place.

Both had originally suspected that iodinewas a compound of chlorine. But before longboth Davy and Gay-Lussac were thinking thatthis might just be a new element. In thosedays, the word “element” didn’t mean exactly

the same thing as it does now. Today, welearn in chemistry class that an element is asubstance made of only one kind of atom. Butin 1813, John Dalton’s atomic theory was onlya few years old, and not everyone accepted ityet. Davy especially didn’t like it. Gay-Lussacthought Dalton was onto something but didn’tsay so publicly because Berthollet felt other-wise. Even so, chemists still talked about ele-ments. To chemists of those days, an elementwas a substance that couldn't be broken downinto simpler substances. In fact, this definitionis just as valid today as it was then. Only nowwe have a microscopic view (where all atomsare the same) to complement the macro-scopic view. Davy and Gay-Lussac both triedto break iodine down, hoping to free the chlo-rine they thought it contained. Neither suc-ceeded, and both suspected that iodine wasn’ta compound of chlorine, but an element in itsown right.

Both Davy and Gay-Lussac publishedtheir ideas. Gay-Lussac beat Davy to press byone day, but each always insisted that he’dreached the conclusion first. Either way, Gay-Lussac probably discovered more new knowl-edge about iodine in the long run. While Davysoon left Paris, traveling with his new bride toItaly, where he studied the chemistry of dia-monds, Gay-Lussac kept studying iodine.Gay-Lussac finally published a 155-pagepaper filled with his experiments and theresults. It was considered the best source ofinformation about iodine for many years.

It took several different scientists to getto the bottom of the puzzle of iodine. Courtois,Clement, Desormes, Gay-Lussac, and Davy allplayed roles. This is how science often works.Many people take part in a discovery, some-times working together, sometimes compet-ing against each other. Sometimes, the worldoutside the lab plays a big part in shapingwhat scientists do. While the path is seldomstraight, the road to discovery is almostalways an exciting one.

REFERENCESCrosland, M. Gay-Lussac: Scientist and

Bourgeois. Cambridge: CambridgeUniversity Press, 1978.

Crosland, M. The Society of Arcueil: A Viewof French Science at the Time ofNapoleon I. London: Heinemann, 1967.

Knight, D. Humphry Davy: Science andPower. Cambridge, MA: Blackwell, 1992.

Mark Michalovic has been an adjunct professor atTemple University and has been involved in chemi-cal education at the Chemical Heritage Foundationsince 1999.


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Gay-Lussac

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Reach Us on the Web at chemistry.org/education/chemmatters.html

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More on elementsIn the Race for Iodine you

looked back at an age where fewelements were known. Today youhave at your fingertips all sorts ofinformation on over 100 elements.For an awesome Web site thatprovides loads of information onthe elements, head to:http://www.chemistry.org/portal/a/c/s/1/acsdisplay.html?DOC=sitetools%5Cperiodic_table.html#

Don’t forget!The deadline for the National

Chemistry Week Poster Contest isJanuary 31, 2007. The theme ofyour poster must relate to thechemistry of the home or homesafety. There are prizes for all agegroups. For more information, seethe online guide at www.chemistry.org/ncw.

Chemists, start yourengines!

The February issue ofChemMatters will feature an arti-cle on a sport that arguably hasthe greatest amount of chemistryinvolved—stock car racing. Vet-eran writer Brian Rohrig will takeus behind the scenes for the excit-ing chemistry behind NASCARracing!

ChemMatters at yourfingertips

Complete your classroomChemMatters set with our 20-yearCD. You'll find every issue from1983 through 2003 along with allof their accompanying Chem-Matters Teacher’s Guides. It iseasy to search and costs only$25. Also, the new 1983–2006ChemMatters Index has been pub-lished and you can get your copyof this print index for only $12.Call 1-800-227-5558, or orderonline at http://chemistry.org/education/chemmatters.html.

As for the He balloonin the car....

As the car turns sharply tothe right (for example) andeverything in the car leans to theleft, the balloon actually acceler-ates to the right — into the turn!There really is no suchthing as

centrifugal force. It’s more themomentum of the objects in thecar and their tendency to continuealong a straight line path. As thecar turns right, the objects insidetend to go straight, it seems thatthey are all being pushed out-ward. All except for the balloon—it seems to get “pushed” inward.But consider the air in the car: italso tends to continue in astraight line and therefore getscrowded to the outside. This cre-ates a pressure gradient sidewaysinside the car, from a high pres-sure on the left side where the airis more concentrated to a lower

pressure on the right. This isjust like the bottom to toppressure gradient causedby gravity in the room.

And whereas that gradientgives the balloon an upward

acceleration, the sideways gradi-ent in the car pushes the balloon

inward (to the right).

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