Chemphasis

“Constantly, consciously,
A. Avogadro will 
Simplify chemistry’s
Math rigmarole,
Working through various
Stoichiometrical
Calcs with his number
Defining the mole.”

This next double dactyl poem, posted on 9 April 2020, blended some historical information about Italian chemist Amedeo Avogadro with some descriptions of the uses of a scientific constant later named in his honor.   

“Constantly, consciously, /
A. Avogadro will /
Simplify chemistry’s /
Math rigmarole.”  
Amedeo Avogadro (1776-1856) examined the relationship of the number of molecules in a gas sample to the volume of that sample, determining that samples with more molecules occupied greater volumes, assuming constant temperature and pressure.  This is true regardless of what the molecules themselves are.  We can see this in the relationship of the variables n (number of moles, which is related to number of molecules) and V (volume) in the ideal gas law: pV = nRT.  Avogadro’s Law, specifically, is often written as V₁/n₁ = V₂/n₂.  An important constant used by chemists, Avogadro’s Number, was ultimately named in Avogadro’s honor, but it would take several more decades for this term to be defined by French scientist Jean Baptiste Perrin.   

In terms of the poetic language used here, Avogadro’s work delved into varied quantitative aspects of chemistry, “simplify[ing]” the subject’s “math rigmarole,” and the number named for him is a constant.      

“Working through various /
Stoichiometrical /
Calcs with his number /
Defining the mole.”
As has been discussed elsewhere in this space, Avogadro’s Number is 6.022 x 10^23 “per mole”: 6.022 x 10^23 is the number of particles of a chemical species in one mole of that species.  The scale of this number allows conversions between the particulate and macroscopic levels.

(The second portion of the poem veers into fiction, since Avogadro himself would not have used Avogadro’s Number, but it was too hard to resist using the double-dactyl word of “stoichiometrical” in one of these poems, once I saw a pertinent list of such words and realized that this chemical term would likewise qualify.)   

“Skillfully, quill-fully:
Madame Lavoisier,
Translating chemistry, 
Husband at side…
Pair works in tandem;
Dephlogisticated air
Named now as oxygen,
Demystified.” 

The 8 April 2020 poem was another scientific biography in shorthand, recounting a famous discovery of the Lavosiers (Antoine and Marie-Anne Lavoisier), two landmark figures in the history of chemistry.      

“Skillfully, quill-fully: /
Madame Lavoisier, /
Translating chemistry, / 
Husband at side…”
Antoine-Laurent de Lavoisier (1743-1794) is renowned as a major figure in the Chemical Revolution: the shift of chemistry towards more systematic investigations.  Often mentioned as a sidenote in chemical histories is the fact that his wife, Marie-Anne Paulze Lavoisier (1758-1836) was herself a scientist; indeed, she translated the scientific documents that facilitated many of her husband’s discoveries (presumably, with a quill!).  This seems worthy of more than a passing comment, and this poem attempts to address that humorously.      

“Pair works in tandem; /
Dephlogisticated air /
Named now as oxygen, /
Demystified.” 
The Lavoisiers’ chemistry insights were many; this poem focuses on one.  The phlogiston theory had been the prevailing understanding of combustion prior to the Lavoisiers’ work.  This theory postulated that combustible materials contained phlogiston, which was released when they burned.  Several scientists, among them English chemist Joseph Priestly, used the phlogiston theory to rationalize aspects of combustion.  The Lavoisiers, through a series of rigorous quantitative experiments, showed that combustion was instead explained by the oxygen theory: when a sample reacts with oxygen, it undergoes combustion, yielding an oxidized product.  

What Joseph Priestly had isolated and referred to as “dephlogisticated air” was thus clarified to be “oxygen,” and the element was named as such by Antoine Lavoiser.  This chemical insight was aided greatly by the work of Marie-Anne Lavoisier, who had the scientific knowledge and language fluency to translate key research articles into French so that her husband could read them.   

The compelling story of oxygen’s isolation and characterization has been told in much greater detail by other writers!  These lines focus on the unique chemistry of the Lavoisiers themselves, highlighting their collaborative research process.  

“Quietly, mightily,
Josiah Willard Gibbs
Formulates concepts for 
STEM fields galore. 
Physical, chemical
Thermodynamical
Tools: spontaneity 
Can be explored.”

Not all of the April 2020 poems were chemistry-focused, so I’ll shift ahead to the next one that was, posted on 6 April 2020.  As highlighted in the hashtags, this was the first poem in a week of “Twitter bios,” in which short biographies of scientists were presented in the double-dactyl poetic form.  In this stringent form, one of the lines should be a single word that is a double dactyl in itself.  While not all of the poems from this week managed this, this first one did, highlighting “thermodynamical” in the sixth line.   

“Quietly, mightily, /
Josiah Willard Gibbs /
Formulates concepts for / 
STEM fields galore.”
Josiah Gibbs was a scientist who made enormous contributions to several scientific fields, “formulat[ing] concepts for STEM fields galore.”   One of his most famous papers was “On the Equilibrium of Heterogeneous Substances”; however, his choice of journal was an obscure one (Transactions of the Connecticut Academy of Arts and Sciences), which meant it took several years for the impact of his important work to reach an appropriately wide audience!  The two adverbs of choice for the double-dactyl structure attempted to highlight this, via the combination of “quietly” and “mightily.”  

“Physical, chemical /
Thermodynamical /
Tools: spontaneity 
Can be explored.”
Gibbs’s work was fundamental to the field of chemical thermodynamics, and several equations and concepts bear his name.  The most famous of these is likely the Gibbs Free Energy, represented with a capital G.  The Gibbs Free Energy is a state function, and the change in this quantity for a given chemical reaction can be quantified (Delta G, or 𝛥G), by taking the free energy of the products minus the free energy of the reactants.  If 𝛥G has a negative sign, it means the reaction will proceed spontaneously (naturally).  

This is a particularly useful quantity for chemists because it defines spontaneity at constant temperature and pressure.  Moreover, it allows chemists to discern whether a process will be spontaneous by considering the system (reaction) alone; this is often more convenient than directly using the Second Law of Thermodynamics, which also defines spontaneity but requires consideration of both a system and its surroundings to do so.     

“A chemist considers attentively
That a property’s named as ‘intensive’; sees
How the attribute meant
Relies NOT on extent.
(Definition denotes independency.)”  

The 4 April 2020 limerick addressed a determination that is often seen in early chapters of introductory chemistry textbooks: classifying whether a property of a given sample is intensive or extensive.  Describing matter precisely is a consistent goal in General Chemistry coursework, and this is one important type of such descriptions.    

“A chemist considers attentively /
That a property’s named as ‘intensive’…”
The extensive/intensive classification of properties is deceptively simple; I often notice in grading that such questions have been more challenging than I intended.  To analyze these topics, it’s thus helpful to “consider attentively.” In this poem’s hypothetical scenario, a chemist will be deciding whether or not a given property is intensive.  

“…Sees/ How the attribute meant /
Relies NOT on extent. /
(Definition denotes independency.)”  
Intensive properties, which do not vary with the amount of a substance, are often most easily classified in opposition to extensive properties, which do vary with the amount of a substance.  

For a specific example, we can imagine we have a sample of ten grams of water at room temperature, then further imagine that we divide that sample in half.  Each half of the original sample contains five grams of water; each half of the original sample is at room temperature.  Mass, then, is an extensive property: each half-sample has one-half the mass of the total sample.  Temperature is an intensive property: it is the same for the total sample and each half-sample. 

The mnemonics I share with students are two-fold.  First, I remind them that an extensive property relies on the “extent” of the sample; second, I note that an intensive property is independent of the amount of the sample, noting the similar prefixes.   

In this poem, after the chemist has “considered attentively,” they correctly conclude that the property is indeed intensive.  Here, “the attribute meant / [r]elies NOT on extent”: the property described is independent of amount.  Further, they remember that the definition of an intensive property “denotes independency.”   

“The careful routines of titrations:
Through meticulous applications,
Technique’s operator
Can use indicator
To quantify neutralizations.”  

The 3 April 2020 poem returned to the limerick form with a summary of a common introductory chemistry experiment: an acid-base titration.  

“The careful routines of titrations… /
In my experience, many students have strong memories of titrations from previous chemistry courses: measuring out the volume of a reactant dispensed through a buret, a precise piece of glassware; carefully swirling around the resulting mixture in a flask, watching for a tell-tale color change.           

“Through meticulous applications, /
Technique’s operator /
Can use indicator /
To quantify neutralizations.”  
Titrations can be used to investigate multiple types of reactions, but many are used to explore the reaction of an acid with a base.  Acid-base reactions are generally called neutralizations, and color-changing, pH-sensitive indicators are used to investigate these experiments.  

In one common type of acid-base titration, a flask is prepared, containing an acid and phenolphthalein indicator, which is clear in solutions with acidic pH.  When the base delivered from the buret has neutralized the acid in the flask, the indicator turns pink, showing that a basic pH has been reached.  If the “technique’s operator” is adept at the experimental set-up, the resulting data about where the color change occurred can “quantify neutralizations”: yielding information about the stoichiometry of the reaction, the molar mass of the acid, and other interesting information.  (While the full chemistry of phenolphthalein is more complex than this brief summary, this narrower pH window is what’s typically investigated in an introductory chemistry course.)  

Titrations require “meticulous applications”: for the specific case described here, the difference between a very pale pink color (the result of a successful experiment) and a more magenta-ish hue involves only a few drops of delivered titrant.  It often requires multiple attempts for an investigator to achieve the most exact results possible, in these experiments.    

“Our molecule’s geometry 
As sketched-out: asymmetric;
We also note an (overall)
Lopsided charge electric.
Electrostatic map thus shows,
Through densely different hues,
Unequ’lly shared covalent bonds:
Polarity ensues.”

The 2 April 2020 poem describes an electrostatic potential map, a visual, color-coded tool with which chemists can quickly assess the variation of electronegativity for the atoms in a given molecule. Understanding a molecule’s polarity (or lack thereof) is an important step in assessing its properties and reactivity. Determining whether a species is polar or non-polar overall can also be achieved via consideration of whether its covalent bonds are polar or non-polar.   

“Our molecule’s geometry /
As sketched-out: asymmetric; /
We also note an (overall) /
Lopsided charge electric.”
In considering a molecule’s polarity, we consider its geometry (shape) and its overall charge distribution; “sketch[ing] out” a molecule allows us to assess these properties quickly.    

Water, for instance, is famously polar.  It contains an oxygen atom and two hydrogen atoms, arranged in a V-shape.  The oxygen atom is highly electronegative: it strongly attracts its electrons to itself.  The oxygen atom takes on a partial negative charge.  Each O-H bond is “polar covalent” and the molecule’s charge distribution is, overall, “lopsided”: the electron density is shifted towards the oxygen atom.  Non-polar molecules can have bonds in which atoms share their electrons equally via non-polar covalent bonds (such as H₂, in which each hydrogen atom behaves identically).  They can also contain polar covalent bonds, if the symmetry of the molecule means these effects cancel one another out overall (as in CO₂, where the oxygen atoms are linearly arranged on either side of the central carbon atom).

This particular poem describes an asymmetric molecule with polar covalent bonds.   

“Electrostatic map thus shows, /
Through densely different hues, /
Unequ’lly shared covalent bonds: /
Polarity ensues.” 
For the molecule described here, an electrostatic potential map would show high electron density (electronegativity) in red and low electron density (electropositivity) in blue: “densely different hues.” Lines 1-4 previously established that the molecule does not have a symmetric geometry. Our takeaway is that our hypothetical species will have polar covalent bonds and be polar overall: “polarity ensues.”  

The inspiration for this poem was the similarity in sound between the final line and “hilarity ensues,” a common trope in entertainment writing.

“Red shift, blue shift:
Spectroscopic
Info proves a
Useful topic.
As the data
Tilt aesthetic,
Make conclusions
Energetic.”

The third poem posted on 2 March 2020 for Dr. Seuss Day was similar in structure to the second, again borrowing from “Red Fish, Blue Fish.”  Here, even the colorful theme of the first line persisted, as this verse highlighted the spectroscopic phenomena known as red and blue shifts.

Somewhat fittingly, this was the last poem I posted before quite a historic “shift” of its own kind: the move of our entire curriculum online in Spring 2020, during the COVID-19 pandemic.   

“Red shift, blue shift: /
Spectroscopic /
Info proves a /
Useful topic.”
A “red shift” is a phenomenon seen in multiple scientific fields.  For chemists, it indicates that the observed wavelength of electromagnetic radiation (EMR) seen for a characteristic signal in a sample has lengthened.  [Within the visible light spectrum (represented by the familiar rainbow of ROYGBIV), red light has the longest wavelength.]  Conversely, when a “blue shift” occurs, the observed wavelength has shortened.  

Multiple phrasings of these concepts can be expressed.  Because wavelength is inversely proportional to frequency and energy, a red shift also demonstrates a shift towards lower-energy and lower-frequency EMR; a blue shift also indicates a shift towards higher-energy and higher-frequency EMR.  (The most precise chemical terms for these effects are “bathochromic” and “hypsochromic,” respectively.  Intriguingly, these also fit the trochaic rhythm present in this poem!) 

For a chemist, this information often arises in spectroscopic investigations, “prov[ing] a useful topic”: giving insight into what type of structural effect in a molecule might increase or decrease the characteristic wavelength at which a particular peak or signal is observed.  For instance, an interaction that stabilizes a particular molecular motion would lead to lower energy and thus a longer wavelength observed for that characteristic vibrational frequency, as demonstrated via a red shift on the pertinent spectrum.      

“As the data /
Tilt aesthetic, /
Make conclusions /
Energetic.”
As stated above, if a sample is exhibiting a “tilt aesthetic” in its spectrum– the presence of a red or blue shift for a characteristic peak, via a fair bit of poetic license– a chemist can often infer important information about a chemical structure or make other “conclusions energetic.”