Categories
April 2019 Limerick Project

Combustion Reactions

“A process denoted combustion
Results in methodic production:
H2O, CO2;
Common products ensue
From a fuel hydrocarbon’s consumption.”

As with the April 5 limerick, the 6 April 2019 limerick addresses another reaction class and how to easily identify it. This specific poem examines combustion reactions and the chemical formulas used to represent specific compounds involved therein.    

“A process denoted combustion/ Results in methodic production:”
This limerick outlines the class of reaction of interest, pointing out that we’ll be able to classify a reaction as a combustion reaction by looking at its characteristic reactants and products (its “methodic production”). The remainder of the poem defines these species more directly.      

“H2O, CO2;/ Common products ensue/
From a fuel hydrocarbon’s consumption.”  
This is the first limerick in my project to exploit chemical notation to obey the rhythmic rules of the poetic form! For the syllables to work here, the third line is read as “H two O, C O two.”  These abbreviations have specific meanings for chemists.

Notably, “H2O” and “CO2” are not formatted correctly, due to Twitter constraints (or at least my lack of knowledge of how to format subscripts and superscripts via that medium!); they should be properly written as H2O and CO2.  These are the chemical formulas for water and carbon dioxide, respectively. The formula for water tells us that each H2O molecule contains two hydrogen atoms and one oxygen atom; the formula for carbon dioxide tells us that each CO2 molecule contains one carbon atom and two oxygen atoms. 

Water and carbon dioxide are the characteristic products when a hydrocarbon fuel [a molecule consisting only of carbon and hydrogen, such as butane (C4H10) or propane (C3H8)] reacts with oxygen to undergo combustion.        

The overall pattern can be seen in the balanced reaction shown below, which represents the complete combustion of propane. 
C3H8 + 5 O2 →  3 CO2 + 4 H2O

Categories
April 2019 Limerick Project

Precipitation Reactions

“Reactions with solid formation,
We classify precipitation:
Mix solutions (aq),
And the (s) formed anew
Will crash out to observer’s elation.”

The next few limericks address specific classes of chemical reactions and how to identify and interpret them: again, a common theme of many General Chemistry courses.  The first, from 5 April 2019, is a reaction type that figures heavily in both introductory chem courses and my interdisciplinary course, Chemistry in Art.   

“Reactions with solid formation,/ We classify precipitation:” 
Much like balancing reactions, another intro-level skill is identifying types of reactions; chemical reactions often have tell-tale reactants or products that allow their classification.  Reactions in different classes follow set patterns, so once we’ve done our classification, we can explore more interesting aspects of the pertinent chemistry.

For instance, a precipitation reaction involves the formation of a solid product called a precipitate; this product “falls” out of solution (parallelling the everyday definition of precipitation).  

“Mix solutions (aq),/ And the (s) formed anew/
Will crash out to observer’s elation.”
To identify a precipitation reaction, we look for a process with two identifying characteristics.  First, the reactants are aqueous solutions (compounds dissolved in water); they are designated as such by the (aq) abbreviation after their chemical formulas.  Second, one product is a solid, which is designated by the (s) abbreviation after its chemical formula. The final line of the poem notes that precipitation reactions are fun to watch, as the solid product “crashes out” of the solution.

Here’s a sample reaction, in which aqueous solutions of potassium chloride (KCl) and silver nitrate (AgNO3) yield a precipitate of silver chloride (AgCl) and a side product of aqueous potassium nitrate (KNO3); we can see the pattern described in lines 3-5 of this limerick:  
KCl (aq) + AgNO3 (aq) → AgCl (s) + KNO3 (aq)   

Precipitation reactions have implications for the interdisciplinary overlap of chemistry and art.  Silver chloride itself is light-sensitive and participates in reactions associated with black-and-white photography.  Some solid precipitates formed in other precipitation reactions are brightly colored and can be used as pigments in mixing and using paints.       

Categories
April 2019 Limerick Project

Stoichiometry

“The task of calcs stoichiometric
Is central to chem’s dialectic.
For reactions, find yield
When this knowledge you wield,
As you monitor products eclectic.”

Another teaching-centered limerick here on Day 4 of this April 2019 project… this one seeks to answer the questions: Why do the concepts of balancing reactions loom so large in so many former chem students’ minds?  Why do we spend so much time balancing reactions in the first place? (What are the disciplinary applications of that skill?)      

“The task of calcs stoichiometric/
Is central to Chem’s dialectic.”
Once a reaction is balanced, we can do a variety of interesting calculations with it; this is a central theme of introductory chemistry.  Learning how to manipulate and use a balanced chemical reaction is the substance of stoichiometry, a word that comes from the Greek for “element” plus “measure.”  A balanced reaction gives rise to the proportions of the reactants and products involved.    

The 1991 version of Father of the Bride, with Steve Martin’s grocery store tantrum, indirectly provides an introduction to these concepts!  In this scene, Martin’s character George has a breakdown when he cannot buy hot dogs and hot dog buns in the same quantities; he dismantles packages of the latter to achieve equivalent amounts of the two. 

Here, George’s “balanced reaction” is:
1 Hot Dog + 1 Bun → 1 Hot-Dog-In-Bun.

He erupts when he cannot purchase his “reagents” (ingredients) in the necessary “stoichiometric ratio” (here, one-to-one).     

“For reactions, find yield/ When this knowledge you wield/
As you monitor products eclectic.”  

One oft-taught application of stoichiometry is predicting the yield of a chemical reaction: how much of a desired product can we obtain, given the starting amounts?  (To return to the cinematic scene cited above, since George has eight hot dogs and twelve buns, his maximum “yield” would be eight hot-dogs-in-buns… to his obvious frustration.)  If a balanced reaction has multiple reactants and/or products, we can apply stoichiometric principles to any of them.

This opens the door to many valuable calculations: the combination of a balanced reaction and an understanding of the periodic table is a particularly powerful tool to “wield.”

Categories
April 2019 Limerick Project

Balancing Reactions

“To balance a given reaction,
Complete an established transaction.
‘Cross the arrow you must
Coefficients adjust:
Conserve mass and ensure satisfaction.”

Many of the April 2019 limericks were written with a potential teaching objective in mind, and the April 3 limerick is one of them.  As I’ve taught the same topics more often, I’ve started to hear more of a rhythm and rhyme when I do so.  

“To balance a given reaction,/
Complete an established transaction.”  
I have had occasion to collaborate with generous teaching colleagues outside of chemistry in the past decade, and thus to benefit from their expertise while hearing their external perspectives on my discipline.  One of the most interesting themes we’ve discussed is that, for non-specialists, learning to “balance reactions” is often one of the most vivid memories of their high school chemistry courses. Balancing a reaction means confirming that the reaction has equal numbers of elements as reactants (on the left side of the reaction arrow) and products (on the right side).

In building on this conversation, it has been illustrative to contrast the skills of chemistry with the discipline of chemistry itself.  In my experience, it’s rare that someone enjoys learning the concrete skill of balancing reactions, but mastering that skill opens the door to many interesting disciplinary applications. The introductory experience is similar to learning piano scales: the skill can open many wonderful doors, but the skill itself (at least for this once-aspiring pianist!) isn’t necessarily the fun part.       

“‘Cross the arrow you must/ Coefficients adjust:/
Conserve mass and ensure satisfaction.”  

Chief among the rules in balancing reaction equations: the only numbers that can change to achieve said balance are the numbers in front of each chemical formula– the coefficients– rather than the subscripts on the chemical formulas themselves.  (Changing the subscripts changes the identity of the chemical species.) 

Further, it’s easy to overlook as one is mastering the skill, but a balanced reaction is an elegant contextualization of the law of conservation of mass; a chemical reaction does not create or destroy matter: it simply rearranges it. 

Categories
April 2019 Limerick Project

Atomic Structure

“Gold foil and a question cerebral
Caused the plum pudding model’s upheaval.
Protons, neutrons— contents
Of the nucleus dense—
Proved a fly in the atom’s cathedral.”

The April 2 limerick summarizes Ernest Rutherford’s “gold-foil experiment,” completed in the early 1900s at the University of Manchester.  The Rutherford Group’s experiment was a crucial step towards the modern understanding of how positively charged protons, neutral neutrons, and negatively charged electrons are arranged in the structure of an atom.  (This has always been one of my favorite “science stories,” especially due to the poetic language Rutherford and his colleagues employed in recounting the experiment.)   

“Gold foil and a question cerebral/ Caused the plum pudding model’s upheaval.” 
Prior to the gold-foil experiment, one theory of atomic structure was called the “plum pudding” model: an atom was predicted to exist with negatively charged electrons scattered through the uniform, positively-charged volume of the atom, as raisins are scattered throughout a plum pudding.  

Ernest Rutherford’s research group investigated atomic structure further by devising an experiment: shooting particles through a thin piece of gold foil, then examining where these particles landed.  If the “plum pudding” model were accurate, the particles would travel directly through the foil, essentially in a straight line. However, the data defied this prediction: some particles were deflected sharply, at random angles, from running into something dense within the atoms!  These data rendered the plum pudding model obsolete.      

“Protons, neutrons– contents/ Of the nucleus dense–/
Proved a fly in the atom’s cathedral.”  

Rutherford described the finding:
“It was almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you.”

He and his group ultimately determined that the “something” that some particles were hitting was the atom’s nucleus, a minute-but-massive volume wherein the atom’s protons and neutrons were gathered.  In Rutherford’s nuclear model of the atom, the dense nucleus accounts for nearly all of the mass of the atom, as well as all of the atom’s positive charge; the negatively charged electrons surround the tiny nucleus in a cloud of mostly empty space. Rutherford characterized the size of the nucleus compared to the atom as “a gnat in Royal Albert Hall”; others pursuing similar investigations restated this metaphor as “a fly in the cathedral.”

Categories
April 2019 Limerick Project

Periodic Law

“The table we call periodic
Took Chem from a set anecdotic
To an orderly art
In which elements chart
Their behaviors and traits episodic.”

 My first poem for the April 2019 project focused on the Periodic Table of the Elements (PTE).  2019 was the International Year of the Periodic Table, marking 150 years since Dmitri Mendeleev’s publication of the first version of the modern periodic table in 1869.  The April 1 limerick highlights why the PTE is central to chemistry as a discipline. 

As discussed in the previous entry, in these brief discussions, I will attempt to provide the minimum context for a poem to make sense to a general audience, within a 280-word count (starting with the first line of the poem itself!). These brief essays are not intended to be exhaustive: any General Chemistry textbook would have far more detail, as well as more precise language. Some pertinent links are provided below to resources with more comprehensive explanations.

“The table we call periodic/ Took Chem from a set anecdotic/ To an orderly art”
Prior to the development of periodic law in the late 1800s, many chemical elements had been studied, but the data regarding these individual elements were relatively random: more anecdotal than systematic.  While different stories recount Mendeleev’s motivation differently, one common theme is that he had recently begun work as a professor, and he was interested in organizing the disciplinary information of chemistry more clearly for his students.  His version of the PTE presented information about chemical elements in a comprehensive, logical manner. (Additionally, the third line nods towards Mendeleev’s work on the visually distinctive table that adorns science classroom walls everywhere: perhaps STEM’s most universal artwork!)       

“In which elements chart/ Their behaviors and traits episodic.” 
In the modern PTE, elements are arranged by atomic number (the number of protons of an atom of each element) into a set of rows and columns.  Each row is called a period; elements in increasingly higher-number periods have increasingly higher atomic numbers and atomic weights. Each column is referred to as a group or family; within each family, elements have similar physical and chemical properties. Thus, overall, the elements’ behaviors repeat predictably, or episodically.  This repetition facilitated the construction of the PTE in the first place, and it allowed for Mendeleev’s prediction of “still-to-be-discovered” elements that would be isolated in the years past 1869, bolstering the PTE’s popularity through its predictive capability.     

The story of how the PTE was organized is compelling, involving far more than one scientist and deserving far more than 280 words. I’ll return to this topic, though, which lets me keep this initial discussion perfunctory. 

 

 

    

Categories
Introduction

Objectives

This virtual space: still uncharted;
My first few attempts have been thwarted.
But thoughts keep repeating:
The time here is fleeting;
Get moving; get writing; get started.

I’ve always thought of myself as both a chemist and a writer, but little evidence exists of the latter role, compared to the former. I’m hoping to change that in terms of my creative routine this year.

The last few years have brought some tentative steps in that direction. Most concretely, I greatly enjoyed a poetic experiment in April 2019, wherein I celebrated the overlap of the International Year of the Periodic Table and National Poetry Month, “five lines at a time,” with a set of thirty limericks over thirty days, shared on my Twitter account. I’ve been meaning for several months to go back and provide some additional context and content, so that the limericks could conceivably be useful/educational, as well as format-appropriate. That intent is my most specific and immediate aim, here. I plan to keep each of these initial entries constrained to 280 words, given their origin in Twitter’s 280-character limit: hoping to keep the discussion distinct and direct.

More generally, the “what I wish I’d known” list gets a bit longer every year, as it applies to both 2000 (as a chemistry student in college) and 2010 (as a new chemistry professor). I’ve thought for a while about attempting to compile and communicate some of that information, and this could be a space for that purpose.

And finally, at the risk of this entry’s becoming a bit of a Mobius strip, I’ve found the rediscovery of creative writing to be restorative during the past few years: writing about writing will be a third common topic here, I imagine. While the techniques or resources I’ve discovered are not remotely new, they have all at some recent point been new to me. I’d thus like to create my record of what has helped, in the hopes that it might conceivably someday help others.

As with so many things, it is daunting to try, but more daunting to consider not-trying! So: to be continued.