Tea transitions

Tea bag is paper. Vapor is from phase
transition of water

Introductory chemistry at my college has a broad audience.  My students are not just potential chemistry major and pre-meds, but I teach geologists, art historians, psychologists and even students who simply want to know more about how the hidden world of atoms and molecules works.

I tell them my job is to help them transition from being science students to scientists -- or rather into people who can critically assess and use the science information they encounter.  Can they filter the junk from the reality?

Enter the Food Babe, whose stirs up real science with fake science and then peppers it with a healthy dose of panic to produce posts that are at a perfect level for my students to read and try to tease out fact from fiction.¹  I couldn't do a better job if I made them up.

This example is about my favorite beverage:  tea.  Are plastic tea bag safe, wonders the Food Babe?

To quote:

"Another temperature consumers need to worry about in tea is the “glass transition” temperature. Here’s the science behind the glass transition temperature or, Tg, and why it becomes dangerous according to The Atlantic: 

“That is the temperature at which the molecule in certain materials such as polymers begin to break down. As a rule, the Tg of a material is always lower than the melting point. In the case of PET and food grade nylon (either nylon 6 or nylon 6-6), all have a Tg lower than the temperature of boiling water. For example, while the melting point of PET is 482 degrees Fahrenheit, the Tg is about 169 degrees. Both nylons have a lower glass transition temperature than PET. (Remember that water boils at 212 degrees.) This means the molecules that make up these plastic tea bags begin to break down in hot water.” (Emphasis is the Food Babe's.)

Since we just finished looking at ways to display information about the phases of materials, this is a great piece to dissect.

Phase diagrams are a compact way to show not only the state a material might be in under a given set of pressure and temperature conditions, but the astute reader can pull some information out about the energies required to get a material to change state, and even something about the forces that hold a material together.

The iconic phase diagram in general chemistry is the one at the right for carbon dioxide.  The diagrams are not difficult to read.  The solid lines indicate conditions where two phases are present, in equilibrium.  So at normal atmospheric pressure (1 atm) and -78.5^oC, solid CO₂ ("dry ice") and gaseous CO₂ are in equilibrium with each other.  At normal pressure, if you heat solid CO₂ above  -78.5^oC, it will change from a solid directly into a gas without melting, it's icy cold, but doesn't produce a liquid when it warms.  It's a "dry" ice.

When a material changes phase, it's important to understand that the core identity of the molecule doesn't change. That is, the structure of the individual molecules does not change, molecules do not 'break down' during a phase change. The CO₂ molecules in the solid are just like the CO₂ molecules in the gas.  What changes in a phase transition is the arrangement of the molecules, their relationships to each other.  In the gas phase, the molecules are widely separated and moving randomly, while in the solid they are arranged in a crystalline symmetrical array, and don't move much.

There are more possible phases for a material than the familiar solid, gas or liquid.  Many materials have several different ways for the molecules to pack themselves into a solid.  (Water has more than a dozen different types of ice, with different densities and other macroscopic properties.)  Some solid forms are crystalline, with all the molecules neatly arrayed.  Others show less order on the molecular level. These forms we call amorphous solids.  Some amorphous solids are called glasses.  At the glass transition temperature, a nice crystalline solid can change into a less ordered glass form.  For a polymer like the PET, the glass transition temperature is when (on the molecular level) the molecules become less rigidly ordered.  On the level we can observe, it means the polymer becomes less brittle, more malleable.  Softer.

It does not mean that the (presumably dangerous) molecules break down and leach into your tea water.  If there is a danger lurking in your fancy PET tea bag (and there might be) - this isn't it.

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1.  The classic example is about airplane travel and gases, where she tries to get people incensed about the 'fact' that the cabin air contains nitrogen because the airlines are too cheap to use pure oxygen, and about pressurized cabins.  It's not only wacky fake science, but a bit scary because she suggests medication doses and timing will have to be adjusted due to the nitrogen content.  (Do not take medical advice from the Food Babe.  She doesn't even know what is in the air she breathes.)

You can't find the airplane air post on her blog anymore, like her infamous microwave post ("For the experiment pictured above, microwaved water produced a similar physical structure to when the words “satan” and “hitler” were repeatedly exposed to the water.") it's been taken down. She's blocked caching, but you can read it here.

Weird words of science: prilled iodine

"Sample of iodine" by LHcheM.
Licensed under Creative Commons
Attribution-Share Alike 3.0 via Wikimedia Commons

I was browsing the paper version C&E News on the train yesterday afternoon, and noticed two back to back advertisements for halogens, one for bromine reclamation, the other for iodine.  Prilled iodine to be precise.  Prilled?  I had a vision of lacy violets frills.

Prills are tiny balls of a substance, formed by letting droplets of the liquid fall from a height (in a prilling tower.) Surface tension has its way and the droplets become spheres, which then solidify.  Many bulk industrial chemicals, particularly fertilizers and detergents, are prilled for easier handling.

Prilling has its roots in 18th century copper mining, referring to beads of high purity copper.

While I rarely buy chemicals, I have purchased iodine flakes for a teaching lab.  The catalog does offer me the choice of "iodine, beads" — prills by another name.

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Fire Burn and Caldron Bubble: A chemistry set for the iPad

From BlueCadet's design for the app

Round about the cauldron go;
In the poison'd entrails throw.
Toad, that under cold stone
Days and nights has thirty-one
Swelter'd venom sleeping got,
Boil thou first i' the charmed pot.

Double, double toil and trouble;
Fire burn, and cauldron bubble.
                            Macbeth, IV.i

Perhaps not surprisingly for the daughter of two chemists, this scene from Macbeth was my introduction to Shakespeare. I loved to hear my father recite the charm the three witches crafted 'round the cauldron.  It was so evocative of visits to my Dad's lab, where vapor from bubbling pots rose to collapse back into liquid form, dripping steadily into flasks.  The sweet-sharp scent of acetone swirled around like mist.   Worrying whether the tomato soup heating in a beaker on a Bunsen burner was safe to eat — poison'd I grasped (entrails were frankly a mystery when I was six, despite my kindergarten teacher's attempt to broaden her small town Midwest children's palates beyond chicken and mashed potatoes).

Though a confirmed theorist (the only things extracted in my lab are coffee and tea), I still love the idea that you can pull a chemical reaction off the paper and, by boiling and bubbling (along with much swelter'ng and perhaps even a dash of dragon's scale), transform the known into the new and very different.  The Chemical Heritage Foundation, where I was a fellow in 2012, has one of the world's largest collection of vintage chemistry sets.

The CHF teamed up with developer BlueCadet to develop an app, ChemCrafter, for the iPad that recreates some of the fun of these classic sets, right down to the bubbling beakers, explosions and fires.  I played a small part in the development, researching some of the more obscure reactions to be sure of the details of what happened.  Among the more fascinating things I learned was that when sodium metal reacts with liquid bromine, there is no reaction until the beaker is tapped (the source I consulted actually gave a minimum required force), then the reaction is explosive.  I'm trying to imagine (1) how someone discovered this and (2) what the experiments to determine the force must have looked like!

We worked hard to be sure the chemistry was as accurate as it could be (bubbles? fire? color?), down to the thermochemistry (yes, you can have fun with Hess' law and yes, the enthalpies of reaction and the points you earn thereby are extensive properties).

ChemCrafter (after the classic Chemcraft chemistry sets) is free and you can download it for the iPad at the iTunes store.

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Watch Rosie Cook talk about the Chemical Heritage Foundation's chemistry sets and learn more about the collection here.

Nitrogen in the snow

We are expecting another round of wintry weather tomorrow, and an article in the local paper noted that the snow and bitingly cold weather we have had recently are good for farmers.  The cold reduces the population of some pests, particularly the species making their way north.  The article also noted that snow contains nitrogen from the atmosphere, providing a little extra boost for lawns come spring.

The atmosphere is roughly 80% nitrogen, in the form of N₂.  The form matters.  Nitrogen gas is very unreactive, so much so that it many "air sensitive" materials are packed under pure nitrogen.  (The part of the air that is reactive is molecular oxygen, O₂.)  Snow certainly contains dissolved nitrogen gas.  Henry's law predicts the solubility of a gas in a solvent, water in this case, as a function of temperature.  It might seem at first glance counter intuitive, but gases are more soluble in cold solvents than in warm (the opposite is true of most solids, as anyone who has tried to dissolve sugar in cold ice tea knows).  An inch of snow contains about 7 milligrams of nitrogen gas per square foot, or about 1/3 of a kilogram in an acre of snow.  Given that fertilizers are spread onto fields at a field of roughly 300 kilograms per acre, it's not much.

The trouble is actually that this nitrogen isn't in a form that easily accessible to plants.  Nitrogen in the atmosphere must first be "fixed" or changed into a more reactive form, typically tetravalent nitrogen (ammonium) which is then converted to the nitrate ions that plants can use.  So where does the useful sort of nitrogen come from?

Industrially, nitrogen is fixed in the Haber process.  Since nitrogen is so unreactive, this requires pressures hundreds of times those of earth's atmosphere and temperatures more likely to be found on the surface of Venus (over 700^oF).  Nitrogen is fixed in the biosphere by microbes, which undertake an elaborate enzymatic dance to do this at low temperatures and pressures (and yes, scientists are on the job of trying to figure out how to get the enzymatic processes to work at industrial scales.)

Lightening strikes also convert minuscule amounts of N₂ in the atmosphere to nitrogen oxides, and industrial pollution has also injected nitrogen oxides into the atmosphere. Industrial pollutants are by far the biggest contributors. The nitrogen oxides become nitrate ions. These are the nitrogen sources that turn a blanket of snow into a gentle fertilizer.

To put it into perspective, snow and rain probably deposit about 5 kilograms total per acre over a year. It's not much, it's not quite all natural (the rates were much lower in pre-industrial days), but it's something.

Isotope and the hidden women of science

It was a century ago today that the word isotope first appeared in print, in a letter to Nature from Frederick Soddy, who would go on to win the Nobel prize in 1921.  Nature Chemistry has a Thesis column by Brett F. Thornton and Shawn C. Burdette ($) to commemorate the occasion, as well as a post up at the Sceptical Chymist.  The post is illustrated with a photo of a plaque which reads "At a dinner party held in this house in 1913 Frederick Soddy (1877-1956) introduced the concept of 'ISOTOPES'..."  Thornton and Burdette also point to the dinner party as the moment when the term isotope was coined.

But Soddy did not coin the word.  The woman who did coin the term, Dr. Margaret Todd, has been gently set aside and one is left to assume that the word came to Soddy out of thin air. Margaret Todd was a physician and novelist, one of the first women to enroll in medical school in Edinburgh after the exams set by the Scottish Royal Society of Physicians and Surgeons were opened to women.  She was gay.  She wrote a popular novel under a male psuedonym, but it's the single word she handed Soddy that is her most enduring authorial legacy.  You need a good Greek term, she told him.  Try this one.

Sweet Hearts and Frogs

Last week I was at a workshop on teaching in British Columbia where I learned to make a string from a stick (if you're talking about teaching, it's really useful to be put in a situation where you have to learn something entirely new). We used obsidian points to scrape the outer layer of bark from dried stalks of dogs bane (Apocynum cannabinum), then pulled free the fibrous layer at the surface.  The instructor warned us about handling the plant before it was dried, noting that the sap could disrupt your cardiac rhythm. The ethnobotanist and two chemists in the group immediately murmured, "digoxin?" As you might imagine, an activity that features obsidian points, bone knives and an open fire doesn't lend itself to a quick search of the literature, so we were left to wonder for the evening.

cymarine

The sap of apocynum plants, such as dogs bane, contains cymarine, which is a potent cardiac glycoside, like digoxin.  The term glycoside indicates these are structures that contain a sugar chemically bound to the rest of the molecule.  The sugary parts of each molecule are the hexagons with the O's in them on the left side.  Cymarine has one such hexose; digoxin has three.  At first glance the molecules might seem very different, but clip the sugars off and the remaining parts of the structures are very similar.

Cardiac glycosides are produced mostly by plants (foxglove, dogs bane, oleander), but toads also secrete them (check out this paper in Heart about someone who took a purported aphrodisiac that contained dried toad venom and died a few hours later from what looked like digoxin poisoning).  So don't kiss any toads, it's not sweet for your heart.

digoxin

Update: Read the Naked Scientists on why people might lick toads: Tripping over psychogenic toads.

Oversharing and zero point energy wands: pseudoscience in the NY Times

While poking around the other day for some general reading material on the zero point energy, I discovered zero point energy wands (which claim to access not my favorite flavor of zero point energy —molecular vibrational — but the zero point energy field of the universe).  A few hours later someone sent me a link to this piece in the NY Times about spiritual cleansing of living spaces (and quotes one of the practitioners on how quantum physics explains it all, see page 2).  I suspect it is time to add another section to my quantum mechanics course. No, no, not instruction on proper wanding technique...you can find that here....but perhaps a brief conversation about how to get a handle on unpacking pseudoscience that has been cloaked in quantum physics jargon and responding to it is in order.

I suspect that when confronted with examples of psuedoscience, most chemists are like me, we jump into lecture mode.  Partly because we think the way the world works is so fascinating, we can't wait to share.  Partly because we think that if we share what we know (and so much of science is about sharing everything from space to materials to results) then people will see the universe works the way we see it works.  Face it, we overshare.

So how to respond, and more to the point, how do I help my students respond?  I wrote a piece recently offering some practical advice on combatting chemophobia for chemists (Nature Chemistry 5, 439–440 (2013), $).  The short version is watch your language, this is not the moment to play the "I call salt sodium chloride" card (even if you do have a jar labeled NaCl(s) on your kitchen counter) and to listen, to try to suss out whether this is a conversation that at its root is about politics or parenting where the science is secondary, this may not be a teachable moment.

But what about language when the jargon is flying the other way?  The book on wanding (which despite enormous temptation, I did not download onto my iPad) throws around words like "scalar" and "phase-locked" and "zero point energy" with abandon, but the meanings have shifted.  Sometime subtly, sometimes they are utterly scrambled.  How can you have a conversation where the words are the same, but the languages incompatible?

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Some thoughts from ChemBark about combatting chemophobia on a broad level.
Sciencegeist hosts a festival unpacking the mysteries of toxic (and not) chemicals
Science Online 2013 takes on chemophobia
And finally, an non-science article from the NY Times that gets the science right: the venerable Harold McGee on wine wands (no zero point energy invoked!)

Quantum quivering

One thing that still stuns me about quantum mechanics is the notion that all molecular motion does not cease at zero degrees Kelvin (despite what you might read in your intro chemistry book).  Quantum mechanics tells us that when molecules vibrate, they can only do so at certain frequencies -- or energies.  Fascinatingly, the ground state vibrational energies (the lowest vibrational energy state a molecule can be) are not zero.  The molecules continue to vibrate, not matter how cold you get the system, you can never freeze out that vibrational energy.  Nor is the so-called "zero-point energy" of a molecule negligible.  The zero point energy of water is about 7 times as large as the thermal (translational) energy at room temperature).   I imagine all these water molecules arrayed in the solid, gently breathing, no matter how much energy you suck out of the system, they keep on vibrating.

Fine, fine, atoms are quantum mechanical objects and I'm willing to believe that the rules are a bit different in this realm, but surely such things are not true of macroscopic object?  Physicists Amir Safavi-Naeini and Oskar Painter have shown that objects far larger than atoms exhibit this quantum effect.  Watch the video to see how they did it!

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While looking for a basic reference on zero point energy to link to, I discovered zero point energy wands...but that's a tale for another day!

A small sip of oxidane

My better half pulled a pitcher out of the refrigerator last night and poured a glass, thinking it was what we usually stock, lemonade. "Um, what is this?" The vibrant green color bordered on neon. "Either margarita or appletini. Given the color, I'd hazard appletini." The face he made was priceless.

As it turns out, the stuff tastes perfectly acceptable, once you get past the name and color. But names definitely matter. If offered a sip of oxidane, would you (should you) drink it?

Exploding expertise

How do we decide who to listen to about something chemical?  I have a piece in Slate this week (on the brouhaha around the teenager in Florida and the exploding water bottle), and someone in the comments feed there thought to comment on my expertise:

Jack Stephens

The author is apparently ignorant of chemistry. The active ingredient in toilet bowl cleaner is not hydrochloric acid, it is sodium hydroxide. Aluminum and sodium hydroxide react to form hydrogen gas.

16 Hours Ago

 from slate.com

· Reply · Like · Flag

Franz Liebkind

Some toilet bowl cleaners (e.g. Lysol's) contain hydrochloric acid in 10-ish percent concentration. It is there to dissolve calcium carbonate deposits (i.e. scale) found in hard water areas. Both HCl and NaOH react with nonbulk Al to produce, among other things, H2 gas. Iirc in the HCl case the reaction should go faster.

Sodium and HCl (or just water!) is much neater and more spectacular. Adolescent pyromaniac curiosity inspired many of us to major in chemistry.

9 Hours Ago

 from slate.com

· Reply · Like · Flag

Franz Liebkind

P.S. USGS says that the water from the Upper Floridian Aquifer, which supplies most of Polk County and Bartow, is moderately to very hard.

I just finished a new Thesis column for Nature Chemistry about the ways in which chemists can (or cannot) communicate with general audiences about chemistry. Is it possible to have nuanced conversations using the word "chemical" and chemistry, or has the word itself chemical accreted so many toxic associations that it can't be rehabilitated? Can chemists have a role in these conversations by virtue of their expertise? (Short answers: Problably not, probably yes, probably not.)

A session at ScienceOnline2013 earlier this year still has me thinking about the disconnect between how chemists want to talk about their field ("did you know that everything is chemicals? just look at how this works! isn't it cool?") and how people process the information we are so enthusiastically providing ("she is a working mother who probably feeds her kids fast food five nights a week and can't possibly care about her family's nutrition so why should I listen to what she has to say about the molecular structure of NutraSweet™?") Addressing the deficit in science knowledge may not in fact help people assimilate what they need to know make informed decisions about things chemical.

For a society who in many ways is so keen on credentials (or how else do those online diploma mills spammers make money), social science research suggests we don't necessarily consider purely those credentials into our decision when we decide who is an expert in a given field. Dan Kahan and colleagues at the Culture Cognition Project suggest that we assess expertise through the lens of our cultural and social affinities as much (or more) as we do through objective credentials.

So when it comes to deciding who you should believe about aspartame, you believe Dr. X who is an "nutritionist, aspartame victim and single mother of three boys" (her doctorate comes from an unaccredited online school) not Dr. Y who does research on molecular structure and is the mother of two boys and is not an aspartame victim (her doctorate comes from a top accredited school).

As for the Slate commenter, I'm rather fascinated that someone could generalize from you don't know what is in toilet bowl cleaner (is the subtext here that I would be above cleaning my own bathrooms?) to you apparently know no chemistry. Could you imagine that a well-trained scientist would not think to look this up even if she doesn't do bathrooms?  (The police report gives the brand of cleaner, which the manufacturer says contains 20% HCl.  Of course, practically it doesn't matter -- both the acid and the base oxidations of aluminum produce three equivalents of hydrogen gas.)