New Perspectives on Teaching Chemistry

The May 2018 issue of the Journal of Chemical Education is now available online to subscribers. Topics featured in this issue include: electrochemistry and corrosion; textbooks; research on the chemistry teacher pipeline, argument-driven inquiry, and online homework; using everyday objects to teach; teaching organic chemistry with games; communication and writing; examining and creating innovative curriculum; computer-aided discovery activities; exploring kinetics; interdisciplinary laboratory investigations; from the archives: applications of 3D printing for teaching chemistry.

Cover: Teaching Electrochemistry through Corrosion

Corrosion is a major concern for all seagoing vessels and represents the single greatest maintenance cost to U.S. military assets and civilian infrastructure. In Teaching Electrochemistry in the General Chemistry Laboratory through Corrosion Exercises, Richard W. Sanders, Gregory L. Crettol, Joseph D. Brown, Patrick T. Plummer, Tara M. Schendorf, Alex Oliphant, Susan B. Swithenbank, Robert F. Ferrante, and Joshua P. Gray describe a laboratory exercise demonstrating the different types of corrosion, the electrochemistry involved, and common methods of preventing corrosion. 

For another experiment on corrosion in this issue, see:

Using Quenching To Detect Corrosion on Sculptural Metalwork: A Real-World Application of Fluorescence Spectroscopy ~ Cory Hensen, Tami Lasseter Clare, and Jack Barbera

For additional content on electrochemistry in this issue, see:

Iodine Coulometry of Various Reducing Agents Including Thiols with Online Photocell Detection Coupled to a Multifunctional Chemical Analysis Station To Eliminate Student End Point Detection by Eye ~ Jeralyne B. Padilla Mercado, Eri M. Coombs, Jenny P. De Jesus, Stacey Lowery Bretz, and Neil D. Danielson

Recycling Metals from Spent Screen-Printed Electrodes While Learning the Fundamentals of Electrochemical Sensing ~ María-Isabel González-Sánchez, Beatriz Gómez-Monedero, Jerónimo Agrisuelas, and Edelmira Valero

Heat Evolution and Electrical Work of Batteries as a Function of Discharge Rate: Spontaneous and Reversible Processes and Maximum Work ~ Robert J. Noll and Jason M. Hughes

Editorial: Textbooks

In this month’s Editorial, Norbert Pienta discusses the traditional textbook model for general chemistry in Is Something New Happening with Textbooks?

Research on the Chemistry Teacher Pipeline, Argument-Driven Inquiry, and Online Homework

In this month’s issue, Gregory T. Rushton and colleagues examine potential leaks in the teacher pipeline that may impact the quality and diversity of chemistry teachers in the United States and suggest ways to improve the chemistry teaching workforce. See: Repairing Leaks in the Chemistry Teacher Pipeline: A Longitudinal Analysis of Praxis Chemistry Subject Assessment Examinees and Scores ~ Lisa Shah, Jie Hao, Jeremy Schneider, Rebekah Fallin, Kimberly Linenberger Cortes, Herman E. Ray, and Gregory T. Rushton

Additional chemical education research articles explore:

Developing High School Students’ Self-Efficacy and Perceptions about Inquiry and Laboratory Skills through Argument-Driven Inquiry ~ Guluzar Eymur

General Chemistry Student Attitudes and Success with Use of Online Homework: Traditional-Responsive versus Adaptive-Responsive ~ Michelle Richards-Babb, Reagan Curtis, Betsy Ratcliff, Abhik Roy, and Taylor Mikalik

Using Everyday Objects To Teach 

Build Your Model! Chemical Language and Building Molecular Models Using Plastic Drinking Straws ~ Luis F. Moreno, María Victoria Alzate, Jesús A. Meneses, and Mario L. Marín

Measuring Yeast Fermentation Kinetics with a Homemade Water Displacement Volumetric Gasometer ~ Richard B. Weinberg

Measuring the Force between Magnets as an Analogy for Coulomb’s Law ~ Samuel P. Hendrix and Stephen G. Prilliman

Is That a Polarimeter in Your Pocket? A Zero-Cost, Technology-Enabled Demonstration of Optical Rotation ~ Patrick I. T. Thomson

Lights, Camera, Spectroscope! The Basics of Spectroscopy Disclosed Using a Computer Screen ~ José J. Garrido-González, María Trillo-Alcalá, and Antonio J. Sánchez-Arroyo

Multipurpose Use of Explain Everything iPad App for Teaching Chemistry Courses ~ Jayashree S. Ranga

Teaching Organic Chemistry with Games

MOL: Developing a European-Style Board Game To Teach Organic Chemistry ~ Eduardo Triboni and Gabriel Weber

Interactive Computer Game That Engages Students in Reviewing Organic Compound Nomenclature ~ José Nunes da Silva Júnior, Davi Janô Nobre, Rômulo Silva do Nascimento, Giancarlo Schaffer Torres, Jr., Antonio José Melo Leite, Jr., André Jalles Monteiro, Francisco Serra Oliveira Alexandre, Maria Teresa Rodríguez, and Maria Joseja Rojo

Communication and Writing

Encouraging the Art of Communicating Science to Nonexperts with Don’t Be Such a Scientist ~ Sarah K. St. Angelo

Engaging Students with the Real World in a Green Organic Chemistry Laboratory Group Project: A Presentation and Writing Assignment in a Laboratory Class ~ Lois Ablin

Writing a Review Article: A Graduate Level Writing Class ~ Omotola O. Ogunsolu, Jamie C. Wang, and Kenneth Hanson

Essential Elements of Collaboration: Understanding How Chemistry Graduate Students Experience Collaboration through International Research Visits ~ Anne E. Leak, Elizabeth Sciaky, Lubella Lenaburg, Julie A. Bianchini, and Susannah Scott

Examining and Creating Innovative Curriculum

Historical Analysis of the Inorganic Chemistry Curriculum Using ACS Examinations as Artifacts ~ Shalini Srinivasan, Barbara A. Reisner, Sheila R. Smith, Joanne L. Stewart, Adam R. Johnson, Shirley Lin, Keith A. Marek, Chip Nataro, Kristen L. Murphy, and Jeffrey R. Raker

Design and Evaluation of a One-Semester General Chemistry Course for Undergraduate Life Science Majors ~ Carly Schnoebelen, Marcy H. Towns, Jean Chmielewski, and Christine A. Hrycyna

Laboratory Curriculum for a Structure, Reactivity, and Quantitation Sequence in Chemistry ~ Chris P. Schaller, Kate J. Graham, Edward J. McIntee, Alicia A. Peterson, Christen M. Strollo, Henry V. Jakubowski, M. A. Fazal, Brian J. Johnson, T. Nicholas Jones, and Annette M. Raigoza

Computer-Aided Discovery Activities

Using Computer-Based “Experiments” in the Analysis of Chemical Reaction Equilibria ~ Zhao Li and David S. Corti

Pedagogical Approach to the Modeling and Simulation of Oscillating Chemical Systems with Modern Software: The Brusselator Model ~ Jaime H. Lozano-Parada, Helen Burnham, and Fiderman Machuca Martinez

Comparing Classical Water Models Using Molecular Dynamics To Find Bulk Properties ~ Laura J. Kinnaman, Rachel M. Roller, and Carrie S. Miller

Computer-Aided Drug Discovery: Molecular Docking of Diminazene Ligands to DNA Minor Groove ~ Yana Kholod, Erin Hoag, Katlynn Muratore, and Dmytro Kosenkov

Exploring Kinetics

Zero-Order Chemical Kinetics as a Context To Investigate Student Understanding of Catalysts and Half-Life ~ Kinsey Bain, Jon-Marc G. Rodriguez, and Marcy H. Towns

Introduction to Time-Resolved Spectroscopy: Nanosecond Transient Absorption and Time-Resolved Fluorescence of Eosin B ~ Erik P. Farr, Jason C. Quintana, Vanessa Reynoso, Josiah D. Ruberry, Wook R. Shin, and Kevin R. Swartz

Interdisciplinary Laboratory Investigations

X-ray Crystallography Analysis of Complexes Synthesized with Tris(2-pyridylmethyl)amine: A Laboratory Experiment for Undergraduate Students Integrating Interdisciplinary Concepts and Techniques ~ Isabel J. Bazley, Ellen A. Erie, Garrett M. Feiereisel, Christopher J. LeWarne, Jack M. Peterson, Katherine L. Sandquist, Kayode D. Oshin, and Matthias Zeller

Let There Be Light: Hypothesis-Driven Investigation of Ligand Effects in Photoredox Catalysis for the Undergraduate Organic Chemistry Laboratory ~ Shuming Chen

From the Archives: Applications of 3D Printing for Teaching Chemistry

This issue includes an article on the Development and Application of 3D Printed Mesoreactors in Chemical Engineering Education by Tahseen Tabassum, Marija Iloska, Daniel Scuereb, Noriko Taira, Chongguang Jin, Vladimir Zaitsev, Fara Afshar, and Taejin Kim. 3D printing has been used for a wide variety of teaching applications in recent years in the Journal, including making instrumentation and models, including:

Teaching UV–Vis Spectroscopy with a 3D-Printable Smartphone Spectrophotometer ~ Elise K. Grasse, Morgan H. Torcasio, and Adam W. Smith

User-Friendly 3D Printed Colorimeter Models for Student Exploration of Instrument Design and Performance ~ Lon A. Porter, Benjamin M. Washer, Mazin H. Hakim, and Richard F. Dallinger

Applying Hand-Held 3D Printing Technology to the Teaching of VSEPR Theory ~ Natalie L. Dean, Corrina Ewan, and J. Scott McIndoe

A Simplified Method for the 3D Printing of Molecular Models for Chemical Education ~ Oliver A. H. Jones and Michelle J. S. Spencer

Creating and Using Interactive, 3D ­Printed Models to Improve Student Comprehension of the Bohr Model of the Atom, Bond Polarity, and Hybridization ~ Karen Smiar and J. D. Mendez

Volumes of New Perspectives on Teaching Chemistry 

With 95 volumes of the Journal of Chemical Education to examine, you will always find a new perspective on teaching—including the articles mentioned above, and many more, in the Journal of Chemical Education. Articles that are edited and published online ahead of print (ASAP—As Soon As Publishable) are also available.

Do you have something to share? Write it up for the Journal! For some advice on becoming an author, it’s always very helpful to read Erica Jacobsen’s Commentary. In addition, numerous author resources are available on JCE’s ACS Web site, including recently updated: Author Guidelines and Document Templates. 

Citric acid is a weak tricarboxylic organic acid. It is highly soluble in water and, once it dissolves in that, it shows weak acidity but a strongly acidic taste which affects sweetness and provides a fruity tartness for which it is widely used to complement fruit flavors in the food and beverage industry. It is also used to mask the unpleasant taste of pharmaceuticals.¹

However, a high content of citric acid in foods and drinks could damage your teeth. Chemical erosion of the teeth occurs either by the hydrogen ion derived from the acids or by anions which can bind or complex calcium. Citric acid seems to be quite aggressive since it can release three moles of H⁺ ions for every one mole of acid; each ion is able to attack the tooth mineral crystal leading to direct surface etching.²

Since various acids are added to food products to boost flavor, reading the food label may be the best way to determine the acid content yet this information is 99% absent. Usually it is indicated that some acids are present but the concentration of them is not. You can determine those values with some chemistry though! Compound Interest created a cool infographic about the nature and properties of acid contained in foods and drink.

Oftentimes, acid-base titration labs are carried out using vinegar as the acid to be titrated. Sometimes this activity is also used to conduct an IA (Internal assessment) for the IB (International Baccalaureate) program. A common activity is to titrate several different vinegars to find the concentration of acetic acid in each brand. The data collected is analyzed and compared. The activity is not that impressive but requires accuracy and the elaboration of data.

My colleague, William, and I were thinking about creating an original activity to engage students in a titration lab. Actually, a lot of different acids beside vinegar can be found at home. If the acid is contained in a solid matrix, it is necessary to get the acid out of that matrix in order to obtain a solution which can be quickly titrated. We considered many of those other acids before asking “Why don’t we extract the acid out of candy?” In general, citric acid is used as a preservative in food, drinks and, of course, candy. It is also denoted by E number (code for substances that are permitted to be used as a food additive in the EU) E330³. A more detailed description of this compound is available in the Journal of Chemical Education⁴ and on PubChem⁵. In a chemistry lab full of teenage students, it is not difficult to find a pack of candies and most of them contain citric acid! We started out with Mentos Now which we used to illustrate how you can titrate citric acid from candy.

titration_set-up.png

Figure 1 - Equipment used for the titration (dark bottle contains Thymol blue indicator.

NOTE: See the Student and Teacher Documents provided below as Supporting Information.

1 - Chemistry Central Journal (2017) 11:22

2 - Monogr Oral Sci. Basel, Karger, 2006, vol 20, pp 66–76

3 - https://en.wikipedia.org/wiki/E_number

4 - J. Chem. Educ., CLIP (Chemical Laboratory Information Profile, 2003, 80 (5), p 480 (accessed 3/25/2018)

5 - https://pubchem.ncbi.nlm.nih.gov/compound/citric_acid#section=MeSH-Entry... (accessed 3/25/2018)

How does the public perceive scientists? If Tweets with the following hashtags are any indication, public perceptions may not match our reality.

#BadStockPhotosOfMyJob

#StillAscientist

#actuallivingscientist

Our communication as scientists/chemists/educators with the general public can help to challenge these misperceptions in a positive way. The article “Encouraging the Art of Communicating Science to Non-experts with Don’t Be Such a Scientist” (available to JCE subscribers) in the May 2018 issue of the Journal of Chemical Education discusses St. Angelo’s integration of science communication in a college’s senior-level seminar.

The seminar combined chemistry content about nanomaterials with its focus on communicating with the public. Along with learning about nanomaterials and their applications, they analyzed real life examples of communicating nanoscience, such as advertisements, company Web sites, and television episodes. For their final project, students delivered an “expert level presentation” on their nanomaterial topic, but also created an outreach presentation on it geared toward communicating with non-scientists. The resulting outreach presentations included videos, a mini-lecture with movie clips, and a dramatic reading.

St. Angelo used the book Don’t Be Such a Scientist: Talking Substance in an Age of Style by Randy Olson as part of the seminar. Olson was a marine biologist, who then moved into filmmaking career, along with training in an acting program. He argues that approaches typically used by scientists to communicate with other scientists are less effective with the general public. He recommends reaching beyond the typical “head” approach by “connecting through the ‘heart’ with emotion or through the ‘gut’ with humor or through ‘lower organs’ with sex appeal” to help engage and appeal to a wider audience. Student presentations used one or more areas—the beauty of nano for heart, humor for gut, and flirtation for the lower organs, while still addressing the science content for the head.

Within the recommendation for using different areas, I dislike a portion of the quote from Olson shared in the article, “The object is to move the process down out of our head, into your heart with sincerity, into your gut with humor, and, ideally, if you are sexy enough, into your lower organs with sex appeal” [my emphasis added]. St. Angelo does temper this when she comments, “Accessing sex appeal may not be desirable, appropriate, or comfortable for every topic, audience, or presenter.” This is particularly true for high school and younger audiences. I also feel that attempts at humor can often feel forced or contrived and fall flat with an audience.

Although the author used the book at the college level, she suggests other situations where it could be useful. Chemistry clubs or other science outreach groups were two audiences that might be connected with the high school level. She suggests a unit on communication to the general public ranging from a week to an entire semester, which is what is described in the article. It could even be for a shorter commitment. In a high school classroom, one could touch on the subject through a current event related to chemistry, by analyzing an article/Tweet/image/video in terms of its chemistry content along with the way it is communicated.

Although I do not plan to read the book, my personal take-away is neatly encompassed by the base of the abstract figure. The Nano-Girl character stands on what can be viewed as a slider bar that one can manipulate further to the substance side or the style side, or to achieve a reasonable balance. It’s a good, simple reminder that my science-related communication does involve both and that I need to be aware of how I have chosen to balance the two.

ed-2017-009638_0003.jpeg

Figure 1 – Reprinted with permission from Encouraging the Art of Communicating Science to Non-experts with Don’t Be Such a Scientist, St. Angelo. Journal of Chemical Education, 95 (5), pp 804 - 809. Copyright 2018 American Chemical Society.

The article presents one resource for talking to chemistry students about communicating science to the general public. Whether you use this resource or not, in a nutshell: “Learning the skills to communicate science to all ages and backgrounds through various media is necessary to continue engaging the public in science-based concepts that are integral to everyday life and to correct misconceptions about modern day scientists and their work.”

More from the March 2018 Issue

Mary Saecker’s post JCE 95.05 May 2018 Issue Highlights brings the monthly round up of the latest collection of articles from JCE. It’s a great overview to help you hone in on what you’d like to read first.

What have you used from JCE lately? Please share! Start by submitting a contribution form, explaining you’d like to contribute to the Especially JCE column. Then, put your thoughts together in a blog post. Questions? Contact us using the ChemEd X contact form

Now that the 2018 administration of the AP Chemistry Exam is in the books, all of us AP Chemistry teachers now have an opportunity to reflect on the year as we turn our attention toward preparing for the fall.

One part of this process is the review of the released Free Response Questions from this year’s exam. Every year the College Board releases the FRQs from the operational exam (Form O, the version of the exam most students in the United States take) forty-eight hours following the conclusion of the administration. The released FRQs since the redesign of the exam in 2014 can be found HERE and questions from 1999-2013 can be found HERE.

The official scoring guidelines will be posted in late summer after the reading of the exam, followed by the extremely valuable Chief Reader Report, scoring statistics, and sample student responses. Until then, teachers around the world post their draft answers on the National AP Chemistry Teachers Facebook Page or the AP Chemistry Teacher Community and reflect on the exam and what we can learn from it.

I strongly suggest that all AP teachers take the time to fully answer every released FRQ in order to gain a deeper understanding and “feel” of the test. Additionally, read the Chief Reader Report when it is released, read what others post online, and engage in the conversation around how the exam is scored. At BCCE this summer, the AP Chief Reader Dr. Paul Bonvallet will give a presentation in which he reviews the exam. It is always a very informative talk.

My draft answers to the 2018 FRQs, as well as my prediction of how points will be awarded are attached to this post as a PDF. I will now reflect on each of the questions, the exam overall, and highlight things that I think teachers, especially new teachers, can take away from this test.

Question 1

(a)-(c) - The question is very straightforward at the beginning, and I enjoyed the unique way the limiting reactant question was presented. I appreciated the use of more than two reactants and that the limiting reactant could be determined without doing much (or really showing any!) mathematics, if a student had a strong understanding of proportional reasoning and immediately recognized the equimolar solutions.

(d) - Reading graphs and glassware to proper levels of precision is an important skill and has shown up repeatedly since the redesign. Only one point on every exam will be awarded for proper significant figures and it will always be a lab scenario. Note that it may or may not be specified for the student to report the value with the proper number of sig figs. My bet is that this was the sig fig question, though others have suggested part (b) given that the volume of the solution provided was so precise (100.00 mL). See  2010 #3 for a very similar question.

(e) - Part (i) is very straightforward, and I liked that they gave a value for the heat capacity of the solution that differed from that of water. I may modify some of my practices to do this, instead of always assuming it to be 4.184 J/g·°C.

Part (ii) is likely going to stir the pot AP teacher community due to the use of the “per mole of reaction” concept. For those who are not familiar, “per mole of reaction” basically means “every time the reaction runs as written”. We will have to wait to see until after the reading which calculated value(s) earned credit. To learn more about this concept, read this article written by James Spencer , the co-chair of the AP Exam Redesign Commission.

(f) - Would a student get credit for simply citing that thermodynamic quantities are intensive properties? Likely not based on conversations I’ve had with previous AP readers. The student would have to explain in their answer that intensive properties do not vary with amount or state their reasoning in terms of “per mole.”

(g) - Remember, just because Question 4 from the Legacy Exam is gone, that does not mean that students do not have to write equations. In fact, this year they had to write three! This was very straightforward, as sodium was the only spectator ion.

Question 2

(a) - I really liked this question. It was a unique way of testing the qualitative aspects of stoichiometry and a reminder of the importance of particle diagrams both for exam success, but also for strong stoichiometric understanding. Have your students draw a ton of particle diagrams, especially in first-year chemistry, when balancing equations and doing stoichiometry.^[1] I wonder how many students did not realize this was a limiting reactant problem…

(b)-(c) - These questions deal with equilibrium and are very straightforward. For b (ii) I wonder how many students got stuck when they hit the quadratic and didn’t know what to do. I hope not many, as the question does not ask for a specific value to be calculated. This is a good reminder that quantitative proficiency does not equate to conceptual understanding and that the AP will never require students to solve a quadratic equation to get an answer to any problem.

(d) - This was a very straightforward bonding question. Have your students practice filling in skeletal structures like this, they pop up frequently for more complex molecules. Two different structures are possible, and would both earn points since students were not asked to consider formal charge.

(e)-(f) - A very simple, straightforward weak acid /strong base titration with predictable questions.

Question 3

(a) - Students will likely forget that the 4s electrons will be removed from an iron atom before the 3d electrons. Some teachers have expressed concern over Aufbau exceptions, but I see no problem here as the Course and Exam Description (CED) does not require knowledge of any exceptions on the exam.

(b)-(c) - Basic atomic structure and Coulomb’s Law questions. I do wonder how specific or vague the wording will need to be for (b) to earn the point.

(d)-(e) - A simple redox titration. I am surprised at the numerous uses of molarity in the FRQs this year. Maybe I am wrong that it is abnormal, but at this point on the exam I was thinking, “wow, more solution stoichiometry!”

(f) - An absurd question, if you know what you’re doing, that got a lot of hilarious posts on social media. Make sure student know proper equipment vocabulary!

(g)-(i) - The wording on part (i) will cause students points here I am afraid and perhaps it could have been phrased a bit more clearly. But with an FRQ that has already been criticized by students and teachers for its length (9 parts, tying the longest FRQs of the redesigned exam with 2014 #1 and 2015 #1). This is likely only to be a single point.

Question 4

(a) - Again students were asked to explain how a non-polar substance can have a higher boiling point than a polar substance. This is a favorite question, it seems, as the test writers try to exploit the common misconception that comes from simply memorizing that LDFs are “weak”.

(b) - A pleasant surprise that must be worth two points. As I say to my students, “Give me the points!”

Question 5

(a) - A good use of particle diagrams to test understanding of weak acids. I would rather them have had to choose which was the most accurate representation. The fact that they were told Figure 1 was better was a huge advantage!

(b) - Students will assume “-x” is negligible even though they calculated it by determining [H⁺]. This will cost many a point. The writers seem to be testing students understanding of when to ignore “-x” in various ways in recent years.

(c) - This will be a bloodbath, just as it was in 2016 #6. Use Q v. K, it is your friend

Both (b) and (c) harken back to 2016 #6 where the modal score was a 0/4. See what was said about this question on what is now called the Chief Reader Report. This is a great question to foster good class discussion.

Question 6

(a) - As far as I know, this is the first time students have been asked to explain the purpose of the salt bridge, as opposed to drawing the direction of ion flow, so it will be interesting to see what phrasing earns credit. Many probably still think electrons flow through it…

(b) - Very simple, get those points! Though the algebraic sign of E^o will likely get many students.

Question 7

(a) - Simple PES identification. It would have been nice to see a follow up question that had more depth, but that means that there was an easy point available for rate constant units in part (b).

(b)-(c) - Straightforward first-order kinetics and half-life question. Teachers and students have been grumbling that it is unfair because nuclear chemistry is not part of the course. However, I do not share their frustration. The CED clearly mentions radioactive decay as an example of first-order kinetics in Essential Knowledge Statement 4A.3(e) under Learning Objective 4.3 and even if it did not, students should clearly recognize that if the half-life is citable, then it must be constant and therefore the process is first-order, no matter what that process is.

I would hope this question scores very high.

Overall Impressions

This was a very fair free response section that was well balanced between conceptual and quantitative understanding. The last few years we have seen a consistency develop in the style of the exam and evidence that it is very faithful to the CED. One of the goals of the redesign was to create an exam that was faithful to a set of standards, not just to previous iterations of exams.^[2] The more exams we see, the more I think that the Test Development Committee is succeeding in this aspect.

What are your thoughts of this years FRQs? I am excited to hear how the reading goes in a few weeks at to debrief at BCCE in South Bend, Indiana with everyone!

^[1] See the following articles and resources about visualizing chemistry using particle diagrams and using the table method (BCA) to solve stoichiometry problems.
Bridle, Chad A. and Ellen J. Yezierski. Evidence for the Effectiveness of Inquiry-Based, Particulate-Level Instruction on Conceptions of the Particulate Nature of Matter. Journal of Chemical Education, 2012;89;(2), 192-198. DOI: 10.1021/ed100735u.
Dukerich, Larry. “Conceptual Chemistry.” https://www.chemedx.org/blog/conceptual-chemistry.
Hemling, Melissa. “Using Visual BCA Tables to Teach Limiting Reactants”, https://www.chemedx.org/blog/using-visual-bca-tables-teach-limiting-reactants.
Posthuma-Adams, Erica. “Simple Activities to Implement Particle-Level Diagrams", https://www.chemedx.org/blog/simple-activities-integrate-particle-level-diagrams.
Prilliman, Stephan J. “Integrating Particulate Representations in to AP Chemstry and Introductory Chemsitry Courses.” Journal of Chemical Education 2014 91 (9), 1291-1298. DOI: 10.1021/ed5000197.
Underwood, Kaleb. “A Visual and Intuitive Approach to Stoichiometry.” https://teachchemistry.org/professional-development/webinars/a-visual-and-intuitive-approach-to-stoichiometry.
^[2] David Yaron. Reflections on the Curriculum Framework Underpinning the Redesigned Advanced Placement Chemistry Course. Journal of Chemical Education201491;(9), 1276-1279. DOI: 10.1021/ed500103e

This year my state adopted our version of NGSS and as a result I have shifted the design of each unit of my curriculum to allow for more student questions and curiosities to drive the instructional flow. The goal of this introductory lesson I will share with you was to utilize the crosscutting concept, structure and function, as a means to model pre-conceptions of a voltaic cell.

The NGSS structural shift begins each unit with a phenomena to engage student understanding. The phenomena do not have to themselves be phenomenal but rather pique curiosity and engage students. To begin the electrochemistry unit I set up a standard voltaic cell with an LED light. The lesson began with a conversation with my students about how many kids at the elementary level science fairs apply the same chemical principles of a voltaic cell to create lemon batteries. Many students themselves admitted they had at some point in time created an at home battery via food at some point earlier in their science education. I then asked them to draw a picture and explain how the voltaic cell works, prior to instruction. To decrease the stress involved in explaining something unfamiliar, the students were instructed to “sell the class” on their story/explanation and it didn’t matter if it was right or wrong.

While I have some high functioning students, not one child/group could actually explain completely why the cell worked as it does in chemical terms. This simple activity hooked my students for the unit and they wanted to know whose “story” was closest to the actual one. Prior to entering my classroom students have taken physical science where they learned about electricity and the mechanism of a circuit. However, this was in seventh grade and they have since taken biology, earth science and chemistry so it’s not unreasonable for students to have an idea of how a voltaic cell works but at the same time it’s been three years. So, the expectation is that they will not remember an explanation. I genuinely enjoyed learning the preconceived ideas students generated for voltaic cells and was happy my students became so curious about finding out whose predicted model was closest to being correct. The following section summarizes the major ideas put forth.

Mobile electrons and ions

Many students focused their explanation of how the voltaic cells worked around the idea of mobile electrons and ions creating current. Students have learned about metallic bonding previously and that metals are good conductors of electricity. Therefore many tried to pull the idea of mobile electrons into their explanations. One group suggested both metal electrodes lose electrons and then enter the solutions and mix with ions which allows a current to flow. Some students described the metal ions in the solution as the means by which the light bulb was lit, but were not able to expand beyond that or explain why the ions moved or why mobile ions were involved in keeping the light bulb lit at all.

student_drawings_of_cell.png

Figure 1 -Two aamples of student drawings of an electrochemical cell prior to learning about the topic.

Transfer of Energy

Some students explained that the metal electrode loses electrons and the ions enter the solution and form an ionic bond with the negative ions in the solution. This process releases heat since bonds are formed and this energy travels to the light bulb and lights it up. A couple of groups mentioned that electrons travel to the light bulb and transfer electrical energy into light energy. Other groups mentioned there is a chemical reaction in the solution that produced heat and since energy cannot be created or destroyed that energy transfer must occur and most likely is that which excites electrons and why we see light.

Light Misconceptions

cell3.png

Figure 2 - Sample #3 of student drawing of an electrochemical cell prior to learning about the topic.

Electrons fall from excited state to the ground state was a common idea for why the light bulb was lit. Students learn about light and spectra in the atomic unit and this idea of energy emission as electrons fall from a higher energy level to a lower energy level was the model that arose in all my classes. Some students mentioned that the mobile electrons constantly collide with each other and generate heat which causes electrons to get excited and jump up to a higher energy level. Other groups stated that the electrons gain energy as they flow through the solution and reacts with the ions to get the electrons excited.

Why is the solution blue?

One group proposed the idea that there was an acid base indicator in the solution and that was responsible for the blue color observed by the copper(II) sulfate. Another group suggested that the solution was gatorade and that’s why people say it’s an electrolyte since it conducts electricity. These two ideas never even crossed my mind, but definitely were conversation pieces in the following lessons!

cell4.png

Figure 3 - Sample #4 of student drawing of an electrochemical cell prior to learning about the topic.

Salt Bridge

Many students mentioned electrons going directly from the metal to the solution. No students was able to explain the purpose of the salt bridge or was able to predict the flow of electrons from anode to cathode. When I probed the purpose of the salt bridge, many suggested that the system must be closed or a full loop. One group explained the salt bridge might be similar to a closed equilibrium system where if the electrons are not allowed to move the circuit does not function.

board1.png

Figure 4 -Whiteboard drawings around the classroom.

The diagrams and boards were all displayed around the room for the unit. We were able to come back to the drawings and re-model how the voltaic system functions at the end of the unit, to describe what happens when food is used as the electrolyte such as the case in a lemon battery. It’s a work in progress, but overall there was better engagement and desire to understand the purpose of each component of the voltaic cell and how it functions. Many students even said this was their favorite unit, which is definitely a plus!

In the January, 2018 issue of the Journal of Chemical Education, Jeffrey Statler describes several experiments that can be conducted with liquid air.¹ He demonstrates that liquid air can be easily collected by simply immersing a test tube in liquid nitrogen, which has a temperature of 77 K. Upon doing so, the air within the test tube is cooled to below the condensation point of air (79 K). Thus, any air that enters the test tube condenses to a liquid. About 20 mL of liquid air can be collected if the test tube is left undisturbed in the liquid nitrogen for 30 minutes. If a strong neodymium magnet is immersed into the liquid air thusly collected, liquid oxygen (which is paramagnetic) is attracted to the magnet!

I have used the method described by Statler several times to condense liquid air. In fact, I have also used other methods to condense air from the atmosphere (scroll below to view a video that displays how to conduct another simple and useful method to condense air). However, I learned several important things by reading Statler’s article. For example, I learned that the liquid collected in this experiment is air and not pure oxygen. Thus, the liquid collected contains mostly a mixture of about 78% nitrogen and 21% oxygen. I also learned that a neodymium magnet can be used to separate some oxygen from the liquefied air. This is fascinating experiment to carry out if you get a chance to do so!

An additional method I have used to extract liquid air from the atmosphere has the advantage that it allows observers to directly see droplets of condensed air form and fall into a container for collection. To do this, a roughly-ridged, deep aluminum pan is filled ¼ full with liquid nitrogen. Next, a corner of the pan is suspended above a Styrofoam cup. The nitrogen cools the pan to a low enough temperature that liquid droplets immediately begin to fall from the corner of the pan and into the cup. Several milliliters of fluid can be collected within 5 – 10 minutes using this protocol. After reading Statler’s article, I decided to collect and test the liquid obtained using this secondary method. You can see the experimental set up and some of my tests in the video below:

After several experiments, my hunch is that the liquid collected is oxygen-rich air. I think this based on measurements of the boiling temperature of the liquid collected (Figure 1). Note that the boiling point of the condensed liquid usually starts out around 83 K, and rises to slightly over 90 K before entirely boiling away. The boiling point of the mixture starts somewhat higher than the boiling point of air (79 K), but lower than the boiling point of oxygen (90 K). Over time, the boiling point of the condensed liquid rises, tending toward the boiling point of oxygen. Thus, it is likely that the air collected is enriched in oxygen because nitrogen gas preferentially boils away due to its greater volatility. For comparison (data not shown) the boiling point of a sample of liquid oxygen was found to remain steady at around 90 – 91 K for several minutes. Likewise, the boiling point of a sample of liquid nitrogen remained steady at around 76 – 77 K for several minutes.

Boiling point of liquid condensed from air

Figure 1 - Boiling point of the liquid collected from an aluminum pan cooled with liquid nitrogen. The initial drop in temperature is due to initial cooling of the thermocouple after immersion in the very cold liquid. The final increase in temperature is due to warming of the thermocouple after the liquid has completely boiled away.

I would certainly enjoy hearing from you if you try out some of these experiments, have suggestions for further experiments, or otherwise have any comments. What are some simple ways you might use to collect liquid air or other liquefied gases?

Happy experimenting!

Reference:

1. Statler, Jeffrey, Microscale Extraction of Liquid Oxygen from a Cryogenic Mixture Formed through Condensation of Ambient Air, Journal of Chemical Education 2018 95 (1), 116-120. https://pubs.acs.org/doi/10.1021/acs.jchemed.7b00436

Part of placing value on the process of learning means giving students multiple opportunities to demonstrate understanding. As a result, retakes are an inevitable part of the process. For many teachers, especially those at larger schools, allowing students to retake assessments is not a philosophical problem, but a logistical one. While creating a whole new assessment has its own baggage, the process of re-learning and the scheduling of who will retake what and when can be overwhelming. To help streamline the entire process, I would like to share a simple strategy that anyone can replicate in a short amount of time, which I have found to help bring a bit of sanity to the organization of the retake process.

When I first started to allow retakes, my system had dramatic flaws. In fact, I am hesitant to even give it the courtesy of calling it a system. I simply told students to let me know when, what, and where they wanted to retake. One student might tell me this information in person while another would send me a message using our LMS. Sometimes the information they provided was incomplete and I would have to chase them down to confirm. Regardless, I would typically write this down somewhere or, even worse, leave it to my memory. This all started to quickly spiral out of control as I was bombarded with messages late at night or approached by students during random times throughout the school day. Each retake request required me to divert my attention from whatever I was doing in that moment so I could write myself a little reminder. To make matters worse, sometimes students would completely change the information they had previously given me and I would have to go back and edit whatever I had originally written down. All of this required the additional step of me generating little reminders to myself on top of the list of obligations and tasks that are a natural part of our profession. My system was designed to fail from the start and, eventually, it did. Something had to change.

After reading a bit about how others implemented their retake policies, I eventually came across a strategy that involved using Google Forms to generate a Reassessment Request Form. By using a specific Add-On within the form, all the student’s answers would be automatically emailed to the teacher in a nice and simplified way. This was exactly what I was looking for—basically a personal assistant to handle the grunge work of scheduling and identifying important information. With a little bit of tweaking to make it fit my needs, here is what I eventually started to do.

Creating a Reassessment Request Form from ChemEd Xchange on Vimeo.

Compared to the lack of structure I had in place before, implementing this simple tool has helped me allocate my attention, time, and cognitive load to things higher on my priority list. I spend less time worrying about the logistics of the retake and more time focusing on helping my students better understand chemistry.

If you have your own retake policy, how do you go about actually executing it? Feel free to share any tips or tools that you think would be useful!

The updated ACS Guidelines and Recommendations for Teaching Middle and High School Chemistry were recently released. The document has been edited and expanded from the 2012 Guidelines and Recommendations to now include information valuable to administrators and middle school teachers. Supporting middle school instructors is important for setting a strong foundation for students and helping them begin making connections between all science courses.

The downloadable document offers advice for organizing the science classroom, support with navigating the core chemistry concepts, and direction for using best practices to support student learning. Important safety information is embedded throughout the document.

Administrators, curriculum directors, middle school science teachers and high school chemistry instructors will find a wealth of information within the text. Please share this information with your science education networks.

I’m sure that many of were inspired to some extent by fascination with explosions, and things that go bang in the night. Generations of chemistry teachers have used the thrills of “boom” chemistry to enliven their classes and demonstrations. Those of us fortunate to have witnessed the class demonstrations of Hubert Alyea at Princeton (documented in a long series of articles in J. Chem. Ed.) were inspired to teach using those methods or just plain enjoyed them.  Whatever your vocation, either in or outside of chemistry, this book makes an enjoyable and informative read.

In the Introduction, the author states that although well researched, the book is not intended for scholarly research. The history of explosives parallels the history of chemistry for the most part. There are no footnotes but the papers and patents cited can be found online. Most chemical compounds have structures illustrated or computer-generated solid models. The Introduction also covers the units of measurement used and definitions of types of explosions and explosives. Not much is known about the author other than that he has written ten other books popularizing science and has a website www.scitoys.com .

The book’s 22 chapters cover specific explosives, uses, or groups of explosives. Chapter 1 begins with a bang with the development of black powder which originated in China in the 7^th century. Black powder is a mixture of nitrates, sulfur, and charcoal. Early uses were for fireworks and rapidly evolved for military uses including bombs, rockets, and fire lances. Preparation of the ingredients is described, especially the nitrates. I’ve always been curious how nitrates were acquired pre-synthetic versions. The chief sources were from processing manure and compost heaps and some recipes from the American Civil War are given.

The extension of black powder to guns and cannons is covered in Chapter 2 and development once again began in China in the 13^th Century. About the same time, gunpowder was first described in England and within a hundred years, firearms were used in the Hundred Years War. Cannons began appearing in European warfare within a hundred years after that. The evolution of handheld firearms and ammunition is described in detail.

The first high explosives, metallic fulminates, are described in Chapter 3. They are high-energy compounds of carbon, nitrogen and oxygen and are typically shock sensitive. There was a pervasive need for better ways to shoot firearms than by flintlocks and their predecessors so the application of fulminates to percussion caps and eventually cartridges for initiation of firing the weapon proceeded rapidly. The remainder of the chapter covers additional high explosives including metal acetylides, triacteone triperoxide, nitrogen trichloride and triiodide, and azides.

Guncotton and smokeless powders are described in Chapter 4. Both are prepared by nitrating cellulose with nitric and sulfuric acids and are improvements over the use of black powder in firearms and artillery. It took some time before explosive uses were discovered. Nitroglycerine is covered in Chapter 5. Alfred Nobel developed dynamite, nitroglycerine absorbed on an inert powder, to enable nitroglycerine to be used safely as a commercial explosive. The text of his 1866 US Patent is included which also details its use as an explosive in boreholes. He also developed ballistite, a gel of guncotton dissolved in nitroglycerine for use as a smokeless powder. However, properties and politics led to the use of British cordite instead.

Picric acid, 2,4,6-trinitrophenol, described in Chapter 6, was originally prepared by nitration of indigo. Almost a century later it was prepared by nitration of phenol. It is a secondary explosive, insensitive to shock and heat, but its metal salts are quite sensitive which produces problems when it’s used to fill artillery shells. On December 6, 1917, the SS Mont Blanc, filled with explosives (mostly picric acid) caught fire after a collision in Halifax harbor, exploded with great loss of life and property damage.

TNT, 2,4,6-trinitrotoluene, is described in Chapter 7. It’s more difficult to detonate so it’s used in armor-piercing shells where a delayed explosion is desirable. TNT melts at 80 °C so it can be cast, which makes filling shells easier. On page 80, a table of relative effectiveness of various explosives is shown, defined, and referred to throughout the book. Chapter 8 describes Tetryl, 2,4,6-trinitrophenylntiramine, which has since been supplanted by the chemically related RDX and HMX, some the most explosive compounds in use. PETN, pentaerythritol, is described in Chapter 9. It is 1.6 times more explosive than TNT It has a neutral oxygen balance (the less oxygen the better to make a high explosive). PETN is used in primacord, a fuse cord to initiate other explosives. Since it is an ester, like nitroglycerine, it is a vasodilator used to relieve angina. The infamous Shoe Bomber tried to use PETN to bring down an airplane in flight.

Chapter 10 covers RDX, also known as cyclonite, which is cyclotrimethylenetrinitramine. The text of the original patent is shown. It has a very high detonation velocity. Blended with a plasticizer, binder, and motor oil, RDX yields the moldable C-4. Blended with TNT and powdered aluminum, RDX is used in antisubmarine depth charges. HMX, a compound related to RDX (cyclotetramethylene tetranitramine) is covered in Chapter 11. It is more stable than RDX and has an even higher detonation velocity. Chapters 12 and 13 describe less common but very energetic compounds including HNIW/CL-20 and TATB (triaminonitrobenzene).

Chapter 14 discusses polymer bonded explosives. The advantages are lowered sensitivity and easier moldability. They are used in detonation of nuclear devices, detonation cord, and torpedo warheads. Testing and properties for determination of explosives are discussed in Chapter 15 and several comparison tables are included.

Chapter 16 discusses the need for less sensitive explosives as illustrated by documenting several accidental explosions. Compounds range from ammonium picrate, nitroguanidine (also used as an insecticide), through several more exotic compounds with cage structures. There is a need for limiting or directing the effect of explosive blasts. Various methods and ingredients for shaped charges are described in Chapter 17. Uses range from effective rock drilling and blasting through armor-piercing shells and in nuclear weapons.

Chapter 18 recapitulates much of the previous material in discussing explosives by chemical class and several newly covered compounds are included. Thermobaric explosives, mixtures of fuels and oxidizer (usually air) are described in Chapter 19. Eco-friendly explosives are described in Chapter 20. Pollution resulting from manufacture as well as use must be considered. Use in civilian applications is especially important in functions including blasting, and firearms. Minimizing the use of lead in any form is more beneficial, including use of copper-coated bullets or tungsten-based bullets (which unfortunately are more expensive). Military and civilian use of TNT will continue because it’s cheap although it has been described as a potential carcinogen. High-energy rocket fuels bring their own list of essential criteria (including pollution) and are discussed in Chapter 21.

Lest the reader come to think that the only uses of explosives are for the military (or civilian blasting), Chapter 22 discusses explosives in the home. The very interesting chemistry and history of phosphorus is discussed and answers questions like “how do safety matches work” and “what is in the paper roll caps used in cap guns”.  Red phosphorus is quite stable but is easily converted to white phosphorus which is quite shock sensitive and self-ignites in air.  Match manufacture is discussed in detail. Carbide cannons, party poppers, and toy rockets are also described.

The blend of the history of explosives and world history in general would probably be more of interest to a general audience. The chemistry, especially the structure/property relationships discussed and chemical energetics, makes this book a valuable supplementary resource for chemistry classes and pedagogy at advanced high school and college levels. Offered at a reasonable price, this book is a must read for many chemical educators.

One of the folks I work with had the opportunity to go to the NSTA convention in Atlanta last month. When she came back, she shared about one of the sessions she attended that discussed having students draw; that drawing was a means of student modeling.

To clarify, this has nothing to do with the Modeling Instruction (at least I am not trained in that pedagogy). This is simply embracing the idea that students already create an image, create an idea, of what is happening when they observe a demonstration, lab or activity. The goal is to have the students make that model more concrete through drawing; and it seems especially prescient as our state has recently approved the Next Generation Science Standards (NGSS) as the Science standards for all students; and as our district begins rolling them out at the high school level next year. Within NGSS, there is an explicit requirement that students develop models of various scientific concepts. So, the idea that a simple drawing could meet that need was intriguing.

I had a reaction rates lab that I thought would be a great trial run for this idea. The students write-up the lab using claim-evidence-reasoning, (CER which has been written about here by Ben Meacham). My goal was to have their drawings help support the ‘reasoning’ component of this write-up. There were four parts to the lab (changing temperature, changing the surface area, changing concentration, and adding a catalyst) and the students had to draw out what they thought was happening in all of the reactions save the catalyst.

This initial run with drawings was interesting and I learned a couple of things. The idea was on the right track: the students did seem to make more connections as to why the reaction rates changed. However, their drawings did not get across anything to someone who had not done the lab. This was partly due to a lack of agreement as to what representations to use. I did not explicitly direct the students, there was no discussion, no consensus, about how to draw particles. The lingering question I had then, was whether that mattered: if a student understands their own ‘model,’ is that good enough?

I decided to be a bit more specific in what I wanted the next time. The next time turned out to be when we electrolyzed water for the Stoichiometry unit. I probably enjoy this activity more than my students, but this is a perk of being the teacher. Most of the time is actually spent getting the test tubes inverted in the cups without air bubbles, but once that’s done the decomposition of water goes really fast. The students can see a lot more gas being produced on the negative side of the battery when compared to the positive side. This is the first part of their drawing (the test tubes and battery, etc.). On the sides of this drawing, I asked that they draw a particle view of what was happening at each thumbtack. I wanted them to be clear about what they thought was happening at those two places and have that reflected in their drawings. Then, they provided a CER paragraph that incorporated their drawings and explained why there were different amounts of gas being produced as the water decomposed, the clue to this being both the formula of water and the balanced decomposition reaction of water that I provided before we started the activity.

Again, there were more lessons for me. First, as this was after we had done a lot with ball and stick drawings and molecular modeling lab/activities, I took for granted that most of the students would see H₂& O₂& H₂O and draw the molecular models. This was definitely not the case. Second, I have to make time for peer review on the drawings. While a student must understand their own model, that model is a means of communicating with other people; it has to be clear, it has to be recognizable, it has to be relatively correct. Someone should be able to look at the drawing and figure out what was going on, even if it’s a simplified model. This also leads to the same issue as before: a need to have agreement/consensus on how particles, molecules, whatever, are presented to others.

As with anything new, the learning curve is steep in the beginning, but I am still convinced it’s the right thing to do and I’m really excited to attempt to improve the process the next time around.

I was doing some kinetic experiments when I came across the V​itamin C Clock Reaction published in the Journal of Chemical Education¹. That reaction is very impressive because of the sudden color change and the simple yet interesting chemistry. I found this chemical kinetics demo very useful. My students are able to see when one reaction ends and the other one steps in. It is easily doable with household items (vitamin C, hydrogen peroxide, starch and tincture of iodine).

I eventually became interested in finding the Vitamin C concentration as well, going over the methods that can be used to determine the concentration of that compound in several products (juices, candies etc). Many household substances can be used, but the product I chose for this activity is Ball^® Fruit Fresh. It is not available in Italy, but a friend from the U.S. brought me some. I would have liked to use some spectrometric methods but I thought they would be too expensive in terms of reagents and subsequent disposal of them.

Figure 1 - Equipment and Chemicals required for the activity.

The method I found the most effective, even in terms of instructional purposes, is titration. In order to determine the amount of a substance such as Vitamin C by titration, we can use iodometry methods. In this kind of process, iodine I_​2 is titrated with sodium thiosulfate through a redox reaction:

2 S​₂O​₃^2​-​+ I​₂​ → 2I^-​+ S​₄O​₆^2​-

Neither the standardization of sodium thiosulfate nor the actual titration of iodine involve the use of dangerous chemicals (except for quite concentrated hydrochloric acid); in addition, the method is relatively easy, quick and accurate.

Iodine is readily reduced by Vitamin C. Knowing the initial amount of iodine in the solution that is reduced by sodium thiosulfate, it is possible to determine the content of Vitamin C in a specific product.

The Reactions

1 - The first reaction takes place between iodate (IO3​-) with excess of iodide (I-​ ​) in acid environment. Iodine (I​2)​ is produced. The solution turns dark-brown.

IO​​₃^-​ + 5 I^–​ + 6 H^+​​→ 3 I​_2​ + 3 H​₂O​

2 - In the presence of Vitamin C, part of the iodine I​₂ is reduced to iodide I^-​ which is colorless compared to iodine. On the other hand, vitamin C is oxidized to dehydroascorbic acid (reagents ratio is 1:1)​:

3 -​ The rest of the iodine is titrated with sodium thiosulfate:

2S​₂O​ ₃^2​ -​ + I​₂​ ​ → 2I^-​ + S​₄O​₆^{2​ -}

Of course, in order to carry out the titration, sodium thiosulfate needs to be standardized (see the teacher document in the supporting informaiton).

With the standardized sodium thiosulfate, students will move on to the titration of the solution containing a small amount of Ball^® Fruit Fresh. (See the student and teacher documents in the supporting information.)

Start adding the Na​₂S​₂O​₃ solution, drop by drop; the mixture in the flask will eventually become clearer, going from dark-brown to a yellowish kind of color. When the solution is light yellow, add a couple of drops of starch solution; you will get a dark-purple color. Continue adding sodium thiosulphate until the solution is colorless. That means that titration process is complete. 

Color changes happening during the process are shown in figure 2.

Figure 2​ - ​from left to right: solutions of KIO₃ after the addition of KI and HCl - solution immediately before the endpoint - solution after the addition of starch - end of titration

This activity was developed as an IA (Internal Assessment) for the IB (International baccalureate) curriculum. Even though I haven't used the activity with an entire classroom of students yet, I worked closely with a student who wanted to test different items containing vitamin C. I did some research to design the chemical method and then we developed the actual procedure. This student and I completed many trials with different substances (including Ball^® Fruit Fresh)  and the method worked very well for us. I also repeated the entire experiment on my own with a defined amount of Vitamin C in order to confirm our results. I hope you can try this procedure in your lab. You can experiment with other substances such as orange juice, vitamin supplements and other household items. I think you will find it useful; calculations are not the usual ones used for a classic acid-base titrations. It may also help you to introduce new concepts in your lessons. If you use it, please let me know how it goes. I am open to suggestions for improvements. 

1 - Wright, Stephen W., Vitamin C Clock Reaction, J. Chem. Ed., 2002, 79 (1), p 41.

In general, the antioxidant activity of a substance is determined by the DPPH assay, published by Blois in 1958¹; that procedure involves the use of a stable free radical (​2,2-diphenyl-1-picrylhydrazyl​) whose electron delocalization gives rise to a purple/violet color. When the DPPH reacts with a substance able to donate hydrogen atoms, the original color eventually fades away due to the reduction of the DPPH itself. The mechanism is shown in figure 1.

Figure 1​ - Reaction mechanism of DPPH with an antioxidant

During my internship period at Sapienza University in Rome, I investigated the antioxidant properties of chitosan, a polysaccharide extracted from crab shells. I am a co-author of an article that discusses the results of that work, Antimicrobial activity of catechol functionalized-chitosan versus Staphylococcus epidermidis​. I worked extensively on that topic and the antioxidant properties were evaluated by the DPPH assay.

What is an antioxidant?

An antioxidant is a substance that even at low concentration is able to either inhibit or delay the oxidation process​. Natural and synthetic antioxidants are routinely used in foods and medicines in order to protect the final product against oxidation. Antioxidants have wide application since they are used as additives in fats, oils and in food processing industries to prevent food spoilage³. It is well known that spices and some herbs are good sources of antioxidants⁴.

The concept of antioxidant might not be easy to grasp; students easily get confused about that and they do not realize that an antioxidant is nothing more than a compound able to be more easily oxidized in order to prevent the oxidation of another (​and probably a more important​) substance. It basically acts as a shield against oxidation. In this blog post, I would like to show a simple demonstration you may use to introduce the concept of antioxidant along with its potential in everyday life.

One of the most famous oxidizing agents in the supermarket is sodium hypochlorite (NaClO), also known as bleach. Sodium hypochlorite is able to destroy the chromophore groups contained in colored compounds such as a food dye. After the destruction of the chromophore, the food dye molecule is not able to absorb light anymore and it will eventually lose its color intensity.

A compound that is widely used as a food dye is tartrazine: it is often labelled either as ​E102 or FDC Yellow 5​. Its molecular structure is shown in figure 2.

Figure 2​ - Structural formula of the food dye & tartrazine (also called FD&C Yellow 5​).

The destruction of the N=N moiety in the molecule, leads to the decolorization of the liquid in which tartrazine has been previously added. It will shift from yellow to colorless. That result can be achieved by adding a couple of drops of bleach into the food dye solution.

Watching Tom Kuntzleman’s video about a cool ​Halloween chemical reaction⁵, I came across Ball® Fruit Fresh​. It is a produce protector as well as a source of Vitamin C and it prevents oxidation of food such as fruit exposed to air (I determined the amount of Vitamin C in that in a ​previous blog post​). I thought it would be fun to test it in order to use “kitchen/under the sink” kinds of chemicals.

By using a spectrometer and some relatively common chemical kinetics, it is possible to demonstrate the antioxidant activity/power of a specific compound, in this case vitamin C. The presence of that compound will delay the oxidation of tartrazine that in absence of an antioxidant is quickly oxidized by bleach.

Figure 3 -​Equipment and household chemicals for the lab

Table 1 -​Equipment and household chemicals for the lab

All procedures can be found in the ​Supporting Information​ at the end of the post.

EXPERIMENTAL RESULTS

Note: the terms Tartrazine, food dye and Yellow 5 are going to be used interchangeably (both here and in the Supporting information sheet). Commercial bleach was titrated and diluted in order to get a concentration of 0.425 M

All the reactions were directly conducted in the cuvette placed in the spectrometer in order to get data as accurate as possible. Tartrazine stock solution was prepared by adding one drop of McCormick yellow food dye to 80 ml of distilled water and bringing the volume up to 100 ml.

Each trial was carried out by rapidly injecting 100 μL of 0.425 M bleach into 3 ml of food dye solution previously poured into the cuvette; by doing that, volume variation is negligible but we are adding an excess of bleach. Absorbance values are collected every 5 seconds. Vitamin C content in Fruit Fresh was previously determined by iodometric titration and data states that 1 g of the product contains 0.127 g of vitamin C.

The solution containing the antioxidant was prepared by dissolving 0.5 g of Fruit Fresh in 50 ml of food dye solution, obtaining a solution whose concentration in vitamin C was 7.21 mM. All the solutions should be filtered before data collection. Spectrometric data was collected by Pasco Wireless Spectrometer PS-2600. A sample of a spectra you could get after the addition of the bleach is shown in graph 1.

Graph 1 - variation of the absorbance of Yellow 5 after the addition of the bleach

Processed data is reported in graphs 2 and 3. By looking at the graphs, we can say that both reactions are first-order reactions with respect to the food dye (lnC vs time plot, where lnC is the natural logarithm of the concentration of tartrazine, gives a straight line with a negative slope).

Graph 2 - Variation of concentration of tartrazine with time

Graph 3 -Natural logarithm of concentration versus time

The action of the antioxidant contained in Fruit Fresh is more evident in Graph 2. Bleach quickly oxidizes tartrazine (​blue circles​) after its addition; as you can see, the concentration of tartrazine decreases pretty quickly over time. On the other hand, in presence of the antioxidant (​green triangles​), the oxidation is much slower. In fact, Vitamin C undergoes oxidation to dehydroascorbic acid, as shown in Figure 4, acting as a sort of shield towards tartrazine.

Figure 4 -​ ​oxidation of Vitamin C (left) to dehydroascorbic acid (right)

The overall reactions, involving Vitamin C and bleach, could be the following one:

C​₆H​₈O​_6​+ NaClO → C​₆H​₆O​_6​ + NaCl + H​₂O​

This reaction is quite fast and counteracts the oxidizing power of bleach toward tartrazine which is actually protected by the ability of Vitamin C to be easily oxidized.
Final data is reported in table 1.

Table 2 - rate constant and half-life values for the reaction in presence and absence of antioxidant agent

In terms of rate constant values, we can consider graph 4. The speedometer represented in the graph above really helps; it’s clear that a higher value of the rate constant, for the same concentrations, corresponds to a faster reaction. In this case, the presence of antioxidant leads to a value of k equal to 0.0144 s^-​1​. On the other hand, in absence of that the value of k is 0.0861 s^-​1​ which means a 6 times faster reaction.

Graph 4 - ​values of k for the reactions experimented in different conditions.

In Italian we would say that the reaction represented by the speedometer on the left is a 500 whereas that one on the right is a Ferrari!

I hope you will find this experiment useful; it involves chemical kinetics and spectrometry so I think it could be beneficial to introduce more advanced concepts in your lessons. I did this experiment with a produce protector as a source of antioxidants but it would be nice to try it out with other substances with a well known antioxidant activity and compare them. In this case, the product I tested was quite soluble in water so no other treatment was required; it could be interesting extracting the antioxidant out of a matrix and test it, not only with bleach but also with other oxidizing agents.

A nice test would be using macromolecular antioxidants; because of their size, those molecules can decrease the activity of the oxidizing agent not only in terms of chemistry but also in terms of molecular motion and diffusion. In fact, a macromolecule could trap the oxidizer into its entanglements, making its path to the target molecules difficult and slowing down the entire process of oxidation.

Resources

     I wish to thank Tom Kuntzleman for his suggestions and advice about this material.

1 - Blois MS (1958) Antioxidant determinations by the use of a stable free radical. Nature 181:1199–12002

2 - Molecules, 2014​, 19(11), 19180-19208

3 - https://www.sciencedirect.com/science/article/pii/S0974694313003733

4 ​- Hinneberg I, Dorman DHJ, Hiltunen R. Antioxidant activities of extracts from selected culinary herbs and spices. Food Chem. 2006;97:122e129

5 ​- https://www.youtube.com/watch?v=UJV04umAb6w&t=92s

"What are we doing to help kids achieve?"

What if you could start all over?  What if you had a clean slate?  Brand new room and equipment?  Furthermore..you have the opportunity to help design it.

The school that I am in was built in the 1970's.  Someone came through Ohio back then convincing everyone that the best new schools should be all open air. They would have one giant building with no walls. The sales pitch worked for awhile. Schools were built as giant spaces. Within a year or two the experiment was over and internal walls were erected. HVAC was a nightmare.

Fast forward to the present day. Our labs have not been touched in years. It was time to remodel. The school board gave the green light for the remodel. The architect provided good news. All of the support walls are on the outside of the building. Internal walls can be torn down within a week. Construction is already under the roof. The architect provided a number of plans. "Tell me what you want. We can reconstruct the walls anywhere. Need a bit more room for testing or make up labs? Want to have common prep space? Would you like flexible seating? Want a fume hood that is shared between rooms? Need extra space for demonstrations?".

I was pleasantly shocked. For years, there have been some rooms and spaces that I have been in that have been less than ideal. Bottom line...I can only control what I can control. I cannot always choose the room or the space but I can choose my attitude to make the best of any situation. Focus on the things I can effect. That has been my mantra. But what if I could make up the dream room? What would I pick and why? I have some ideas...

First and foremost....safety. It does not matter what is happening. The best leson plan gets ruined if a student gets hurt.

Hands on experiences. The best way to learn science is by doing science. Can kids easily enter the classroom and experience science in a safe hands on manner? Does the space allow for that?

Information. Are students able to work together with proper technology to process the information in a timely manner? What if I ditched every poster I had and replaced them for a few LED screens. Students would get timely information about the focus of the day or the lab we were doing on multiple screens as they entered the room. Better yet, they could display their data quickly and effectively for all to see.

Flexibility. Are there safe and reliable ways to transition from labs, to assessments to various types of group work?

It boggles my mind. This was the first time ever that I had an architect seriously ask me the question, "What do you think?"  It has been a crazy couple of weeks with the realization of that question. We have been grading, doing labs, giving exams and working extra hours packing and pitching supplies and chemicals. Did I mentioned that construction started a week before school ended? During my 7th bell class on a Friday I heard some loud pounding. People were in our shared office with sledge hammers. I calmly left my class for a second and approached a guy with a hard hat. "Uhh...can I get a few things off my desk?" He just looked at me. "You better hurry". Students had questions. "Since it is the last day before exams and stuff is getting trashed, can we write on the walls?" It was the last ten minutes of class during 7th bell at the end of the year. "As long as it is school appropriate..." was my response.

Imagine if you could start all over with a brand new classroom! What would you want or do in your dream room? Please let me know. The exhaustion and fog of the end of the year is starting to lift. The new possibilities seem exciting. So what would you do? I would love to hear your ideas....

When I first made the big switch to standards-based grading, I had a hard time reconciling the way I graded throughout the semester and the idea of final exams.

In my district, the final exam is worth 20% of student’s semester grade. All of my grading throughout the semester was formative, and the final exam was so summative. In the past five years I have wrestled with the questions, “what is the purpose of a final exam” and “how do I incorporate a final exam into my grading system.” At this point, I have found peace in answers to both of these questions and part of that relies on my students completing an electronic portfolio.

My answer to the first question is, “a final exam is a summative assessment that students have been preparing for the entire year with a semester worth of formative assessments and feedback. The final exam is their chance to show what they know. The final exam can be an effective assessment tool if written appropriately.” I make sure my exam equally covers all of the learning targets my students were assessed on that semester, no more, no less. This ensures that my expectations for my students are clearly defined.

My answer to the second question is, “I will enter a final exam grade with no curve (aside from a poorly-designed question I may toss after item analysis) to be calculated into a student’s final grade according to district policy. In addition to the actual test, a small percentage of the final exam grade will come from an electronic portfolio completed by students throughout the semester.”

Over the years my electronic portfolio project has changed in format but the purpose remains the same; to encourage students to reflect on and record what they have learned throughout the course. 

Right now I have students completing their portfolios in Google Slides. They previously used Google Sites but it was cumbersome to work with. The nice thing about Google Slides is I can make a template and easily distribute and collect it through Google Classroom.

Here are the directions I give my students: “You should have 1 slide for every learning target we have covered this semester. Each slide should include a picture of a question you did correctly (or corrected) for this learning target as well as an explanation of your work. This will serve as your study guide for your semester exam. Your goal in the explanation is to explain to a future you how to complete the problem when you have inevitably forgotten what to do.”

Figure 1 - Directions slide for electronic portfolio

I also provide students with an exemplar slide so that my expectations are clear.

Figure 2 - Exemplar slide for electronic portfolio

I spend a day in class with students setting up their portfolios. I also give them time in class throughout the semester to work on them. Artifacts do not have to be solely from quizzes, they can be from reassessments or worksheets. Artifacts also do not need to be work that was originally correct. Students can make corrections and then explain what they changed in their portfolio. One of the reasons I love incorporating an electronic portfolio into the exam grade is it continues to encourage my students to be reflective learners, which is one of my main goals in using standards-based grading. Many opponents of standards-based grading cite that it does not prepare students for college because it is not the way college professors grade. I believe that teaching my students the skills to be reflective learners and ensuring they retain content will be more useful to them in the end than teaching them how to cram for a test. I go into more depth about my use of standards based grading in a post titled, "Standards-based Grading in the Chemistry Classroom".

Do you ever struggle with the concept of writing and grading exams? How do you “make peace” with high stakes testing? 

"What are we doing to help kids achieve?"

If you are like me, you get stuff in your inbox all the time about people selling nerdy science stuff to nerdy science teachers. It is hard to know what to ignore and what to get excited about. There was one particular email this year that made the rounds of our science department. The city of Cincinnnati has a "Fringe Festival" each year. It is two weeks of small independent performances, shows and plays all over town. This year one of the plays was "Curie Me Away!". It is about the life and times of Marie Curie. A little company called Matheatre has developed several plays about math and science. They travel to schools and museums throughout the country. The goal is to combine theatre and science. From my experience, they are doing a great job.

You would think that a one hour musical about Marie Curie might not be that great. I am sure people thought that a three act hip-hop and rap musical about Alexander Hamilton could never be great either, ;but look how that turned out. I have to admit, I was a bit leary. The first thing I did was contact Sadie Bowman who is one of the creative engines behind the play. Here is what she had to say.

What made you decide to combine theater along with math and science?

Our company, Matheatre, started in 2006 with a production called Calculus: The Musical! It was written by myself (a comedy/theatre/music nerd) and my colleague Marc Gutman (a high school math teacher). Marc had been creating parody tunes to help his students understand and remember rules and formulas by setting them to familiar music, and it worked so well for his students that he set out to create a song for every major concept in his Calc I class. I suggested taking it a few steps bigger and sharing it with the world, so we wrote a two person comedy show about the history and major concepts of Calculus, featuring these songs. We quickly found that it filled a niche that teachers and students all over North America were hungry for, and the show was a surprise hit. It has been running continuously since that time. Marc and I toured together for two years then licensed the script to a regional theatre here in Cincinnati (Know Theatre), who ran their own national tour from 2008-16. Then in 2016 we (Matheatre) took it back, did a big update/rewrite, and relaunched the company with an expanding repertoire. By this time I had joined forces with Ricky Coates, an actor-writer with a physics background. He had written a one-man play about Nikola Tesla and we realized that touring his show, with content pertaining to physics and electrical engineering, alongside an updated version of Calculus: The Musical! would be a sensible idea. So now Ricky and I are touring full time and Marc is our business/finance manager. We love using the performing arts as a creative access point to science and math. We love that for some students, having music, comedy, or a dramatic connection to the people or the concepts may be just the angle they need to make something click, and for some students the math and the science are easy but maybe they've never had a live theatre experience that spoke to their interests before. We're really all about combining arts and science to inspire new connections or perspectives. It's really rewarding all around.

How long has this particular play been going?

Curie Me Away! debuted in the summer of 2017, so it is our newest show. Ricky and I wrote the script together and I wrote all the music and lyrics (no parodies this time, haha).

What does the future hold?

We will continue to tour to educational institutions for the foreseeable future. We have a new production in the hopper which we hope to debut next summer. It is another story inspired by some prominent characters and an important moment in the history of science--I can't say much about it publicly yet, except that you can expect some sweet 1970s hairstyles. :-) This coming year we have a goal to work with more science museums in addition to schools and universities. 

What was the inspiration for this particular play?

There are so many messages from Madame Curie's experience that are relevant today. I am particularly inspired by her approach to education as an act of empowerment and resistance. Understanding that, as a young woman in occupied Poland, she had to risk her own safety just to learn about science, let alone BE a scientist, and that she was a quiet champion for the potential of EVERY PERSON to be a great mind if they only have access to education, is just a staggeringly noble legacy, in my mind. I want students to feel inspired to pursue their own curiosity and never stop learning, as it feels to me like our culture is becoming more and more discouraging to pursuits of the mind. Her story also inspires the tenacity of girls and women in STEM fields, and in Pierre we have a supportive example for boys and young men to be an ally to the non-male people in their lives. She is just the perfect heroine for a show about chemistry! We worked with Ricky's sister Dr. Becky Coates, a Ph.d in Physical Chemistry, to incorporate core concepts. I wanted to craft lyrical metaphor that would use chemistry themes to further the plot and character development. We tried to find a balance between scientific content and a universally accessible story. If you know the science there are bells that will ring on different levels, if you're new to the science you'll still understand the drama but (we hope) be curious about the science that's just under the surface.

If a school or community would like to sponsor a show....is that possible?  What are the steps?

Yes! We will travel to pretty much anywhere. All three of our productions (Curie Me Away!, Tesla Ex Machina and Calculus: The Musical!) are available and I'm happy to answer questions if interested parties email me at sadie@matheatre.com. We are online at www.matheatre.com. 

I saw the play in a renovated church with about 50 other people ( a sold out crowd). It was a masterful performance. The content was quick witted, clever, had fun songs and did a great job of presenting analogies about chemistry and life. It was a two person performance. Due to extremely clever staging and puppets, it seemed as if there were twenty people rather than a cast of two. It was about one hour long. It was a play about history that could and should be a great lesson for today. Marie Curie was portrayed as a smart intelligent persistant woman who overcame odds and stayed the course to become a great scientist. The play also illustrated her struggles with Pierre, fame and chemistry. The chemistry was spot on. The writers did a wonderful job of comparing chemistry to life. This is a play is one that I can highly recommend. If you get a chance to bring this play to your school, do it! And...if anyone asks...radishes are the food of intellectuals (you need to see the play to get this one..)

My colleague, LaVetta Appleby, and I recently published a letter in the Journal of Chemical Education entitled “Black Panther, Vibranium and the Periodic Table.”

Why should you read our letter? In this activity, we share how we utilized the Disney movie, Black Panther,¹ to discuss the Periodic Law. As chemistry educators, it is imperative that we try to make key connections to student experiences and classroom content, which is critical for effective student engagement in the STEM (Science, Technology, Engineering, & Mathematics) disciplines. If vibranium existed, where do you think it belongs on the periodic table?

Black Panther also provides a platform to engage in a national dialogue about the important contributions of women and people of color to STEM.

Citations

1 - Watch the Black Panther trailer @ https://movies.disney.com/black-panther (accessed 6/11/18)

2 - Collins, S.N.; Appleby, L., Black Panther, Vibranium and the Periodic Table, Journal of Chemical Education, Article ASAP, 2018, DOI:10.1021/acs.jchemed8600206. The letter is open-access without a subscription to   JCE. (accessed 6/11/18)

Acknowledgements

We would like to thank Lawrence Technological University general chemistry students enrolled in University Chemistry 1 during the Spring semester.

Lawrence Technological University also published a press release about the JCE article cited.

How do you demonstrate the workings and effectiveness of buffers in your acid-base unit?

In our acid-base unit, we define buffers as a two-component system that prevents a major change in pH. More specifically, a buffer is comprised of a weak acid and its conjugate base or a weak base and its conjugate acid. Any small amount of strong acid or base added to a buffer is converted to the weaker acid or base already comprising the buffer system, thus, minimizing pH change. We have several examples of where buffers are at play: living organisms, seawater, certain foods or other items meant for human consumption, etc. But, how do YOU demonstrate how a buffer system works?

Last month as we wrapped up our acid-base unit and approached buffers, I did some brainstorming. Here’s a description of what I devised (and it worked well!).

1. Set up 4 beakers. Two with distilled water and two with a buffer of your choice. I “borrowed” a pre-made buffer from the biology teacher. Note: a common misconception among students is that buffers have a neutral pH. Remember that buffers can be slightly acidic, slightly basic, or neutral depending on the composition.

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Figure 1 - Buffer demo set-up.

2. Obtain a dropper bottle of 1M HCl and 1M NaOH.

3. Attach a pH probe to a sensor interface. Our department has provided a LabQuest Mini to each science teacher for demos and we have a set available for labs. What’s great about these interfaces is that you can plug into a PC laptop or MacBook that has Vernier software downloaded or plug into a Chromebook that has the “Graphical Analysis” app set up. I used my staff Chromebook and Google Cast for Education to display the data collection on the projector in real-time.

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Figure 2 - Vernier LabQuest Mini  

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Figure 3 - Projection  of graph using Google Cast for Education

4. Insert the pH probe (with data collection on) into a beaker with distilled water. Show them how the pH is constant (for some reason it was not 7 for me, but I cared more about the qualitative data students were about to observe). Then, add a drop or two of a strong acid. Observe the sharp decline in pH.

5. Now, insert the pH probe into a beaker with the buffer. Observe a constant pH data collection before adding a drop or two of a strong acid. You’ll notice the change in pH is minimized compared to the control experiment (strong acid in distilled water).

6. Repeat steps 4 and 5, this time using strong base.

chemedx_buffer_data.jpg

Figure 4 - Projection of data using Google Cast for Education

7. Encourage a class discussion or ask probing questions (no pun intended) about this phenomenon of buffers. Please note that in upper-level classes you’ll be able to bring in the Henderson-Hasselbalch equation. I did not do this for my non-Honors course.

I hope sharing this demo (and use of a Chromebook) is helpful to you. Do you have anything you would add or do differently for your students?

The University of Waterloo is doing another collaborative project! If you missed out on participating in our 2011 Periodic Table Project, this is your opportunity to have your students celebrate and be part of a worldwide initiative.

Teachers act as our contact and apply to have their class design a tile for one assigned element. Once assigned, it is up to the teacher to determine how the class will design their tile for that assigned element. It can be a contest, a bonus project or part of your study of the elements. Whichever approach is taken, the project should highlight the creative talent of young people in chemistry. The project celebrates 2019 as the International Year of the Periodic Table of Chemical Elements (IYPT 2019), which coincides with the 150th anniversary of Dmitry Mendeleev’s published periodic table in 1869.

You may remember our 2011 Periodic Table Project (below), which produced a wall mural, free mobile app and classroom posters. This time we decided to take a different approach to the table and deconstruct it into the years the elements were discovered. Our goal is to have chemistry students from around the world join together to create an original and imaginative version of the Timeline of Elements focused on their discovery.

2011 Periodic Table Chem13News

Figure 1 - Chem13 News Periodic Table Project 2011

Simply apply for an element on our Timeline of Elements website— there is no cost to participate and the form will take 5 minutes to fill out! Our last project had all the elements taken in the first six weeks and we ran out of elements. This time we will be opening up the application process until August 7, 2018. If more than 118 schools apply, a lottery will determine participating schools. The actual artwork deadline for tiles will be March 15, 2019 (So second semester students can participate!) We will be tweeting all the submissions so follow us @Chem13News.

Figure 2 - Timeline of Elements Project 2019

Dates & Deadlines

Fill Online Registration Form ... May 15 - August 7, 2018

Elements Assigned by Email ... September 2018

Electronic Submission of Artwork ... March 15, 2019

Creation of Collaborative Project (poster, website, wall mural) March ... June 2019

Register on the Timeline of Elements website

Making Connections

The June 2018 issue of the Journal of Chemical Education is now available online to subscribers. Topics featured in this issue include:  investigating nanoscopic structures, innovative curriculum, inquiry-based investigations, using games to teach, outreach on climate change and research ethics, instrumental analysis, organic chemistry laboratory experiments, scientific data analysis, chemical education research, from the archives: food dyes.

Cover: Investigating Nanoscopic Structures

Some of the most beautiful and awe-inspiring insects are blue Morpho butterflies. In Investigating Nanoscopic Structures on a Butterfly Wing To Explore Solvation and Coloration, Brittany A. Bober, Jennifer K. Ogata, Veronica E. Martinez, Janae J. Hallinan, Taylor A. Leach, and Bogdan Negru present a laboratory experiment that introduces general chemistry students to material science and nanotechnology with the use of iridescent Morpho butterfly wings. The nanoscopic structures make the wings superhydrophobic and also form a photonic crystal responsible for the structural coloration of these butterflies. Students performing the experiment alter both the color and superhydrophobicity of the wings of a preserved specimen, as shown by the image of a Morpho butterfly. The background image is a scanning electron micrograph of silver-coated wings that reveals the nanoscopic ridges of butterfly scales responsible for superhydrophobicity and structural coloration. This captivating and memorable experiment for students reinforces their understanding of the properties of light and solvation.

For another experiment on nanotechnology in this issue, see: Reduced Graphene Oxide Joins Graphene Oxide To Teach Undergraduate Students Core Chemistry and Nanotechnology Concepts ~ Izabela Kondratowicz, Małgorzata Nadolska, and Kamila Żelechowska

Editorial: Citations in Submissions

In the June Editorial, Norbert Pienta discusses citations as an important component for scholarly publication in Keeping It Scholarly: Citations in Submissions.

Innovative Curriculum

A Single Reaction Thread Ties Multiple Core Concepts in an Introductory Chemistry Course ~ Meredith H. Barbee, Robert G. Carden, Julia H. R. Johnson, Cameron L. Brown, Dorian A. Canelas, and Stephen L. Craig

Developing Awareness of Professional Behaviors and Skills in the First-Year Chemistry Laboratory ~ Scott Chadwick, Mackenzie de la Hunty, and Anthony Baker

Inquiry-Based Investigations

Solubility from the Femtoscale to the Macroscale ~ David W. Pollock, Giovanna T. Truong, Jessica L. Bonjour, and John A. Frost

Unexpected Discovery: A Guided-Inquiry Experiment on the Reaction Kinetics of Zinc with Sulfuric Acid ~ Martin Rusek, Pavel Beneš, and John Carroll

Using Games To Teach

Prediction! The VSEPR Game: Using Cards and Molecular Model Building To Actively Enhance Students’ Understanding of Molecular Geometry ~ Erlina, Chris Cane, and Dylan P. Williams

Escape Classroom: The Leblanc Process—An Educational “Escape Game” ~ Nicolas Dietrich

Outreach on Climate Change and Research Ethics

Expanding the Educational Toolset for Chemistry Outreach: Providing a Chemical View of Climate Change through Hands-On Activities and Demonstrations Supplemented with TED-Ed Videos ~ Solaire A. Finkenstaedt-Quinn, Natalie V. Hudson-Smith, Matthew J. Styles, Michael K. Maudal, Adam R. Juelfs, and Christy L. Haynes

Interactive Poster Survey Study of ACS Members’ Knowledge and Needs on Research Ethics ~ Patricia Ann Mabrouk and Susan M. Schelble

Instrumental Analysis

Determining the Deacetylation Degree of Chitosan: Opportunities To Learn Instrumental Techniques ~ Leyre Pérez-Álvarez, Leire Ruiz-Rubio, and Jose Luis Vilas-Vilela

Surveying Iodine Nutrition Using Kinetic Spectrophotometry: An Integrative Laboratory Experiment in Analytical Chemistry for Population Health ~ Adriana Nori de Macedo, Stellena Mathiaparanam, Ritchie Ly, and Philip Britz-McKibbin

Teaching Undergraduates LC–MS/MS Theory and Operation via Multiple Reaction Monitoring (MRM) Method Development ~ Thomas A. Betts and Julie A. Palkendo

Organic Chemistry Laboratory Experiments

Isobutylene Dimerization: A Discovery-Based Exploration of Mechanism and Regioselectivity by NMR Spectroscopy and Molecular Modeling ~ Mariah L. Schuster, Karl P. Peterson, and Stacey A. Stoffregen

Probing the Reactivity of Cyclic N,O-Acetals versus Cyclic O,O-Acetals with NaBH₄ and CH₃MgI ~ James A. Ciaccio, Shahrokh Saba, Samantha M. Bruno, John H. Bruppacher, and Alexa G. McKnight

Room-Temperature C–H Functionalization Sequence under Benchtop Conditions for the Undergraduate Chemistry Laboratory ~ Shuming Chen

A ³¹P{¹H} NMR Spectroscopic Study of Phosphorus-Donor Ligands and Their Transition Metal Complexes ~ Ethan C. Cagle, Timothy R. Totsch, Mitzy A. Erdmann, and Gary M. Gray

Continuous Flow Science in an Undergraduate Teaching Laboratory: Bleach-Mediated Oxidation in a Biphasic System ~ Vanessa Kairouz and Shawn K. Collins

Continuous Flow Science in an Undergraduate Teaching Laboratory: Photocatalytic Thiol–Ene Reaction Using Visible Light ~ Jeffrey Santandrea, Vanessa Kairouz, and Shawn K. Collins

Empowering Students To Design and Evaluate Synthesis Procedures: A Sonogashira Coupling Project for Advanced Teaching Lab ~ Jun-Yang Ong, Shang-Ce Chan, and Truong-Giang Hoang

Scientific Data Analysis

Least-Squares Analysis of Data with Uncertainty in y and x: Algorithms in Excel and KaleidaGraph ~ Joel Tellinghuisen

Revisiting the Scale-Invariant, Two-Dimensional Linear Regression Method ~ A. Beate C. Patzer, Hans Bauer, Christian Chang, Jan Bolte, and Detlev Sülzle

Scientific Data Analysis Toolkit: A Versatile Add-in to Microsoft Excel for Windows ~ Arthur M. Halpern, Stephen L. Frye, and Charles J. Marzzacco

Chemical Education Research: Course Selection Factors, Acid-Base Topics for Teaching Nursing, and Primary Research in the Teaching Lab

Investigation of the Factors That Influence Undergraduate Student Chemistry Course Selection ~ Elsa M. Hinds and Ginger V. Shultz

Identifying Relevant Acid–Base Topics in the Context of a Prenursing Chemistry Course To Better Align Health-Related Instruction and Assessment ~ Corina E. Brown, Melissa L. M. Henry, and Richard M. Hyslop

Integrating Primary Research into the Teaching Lab: Benefits and Impacts of a One-Semester CURE for Physical Chemistry ~ Leah C. Williams and Michael J. Reddish

Additional Teaching Resources

The InChI Code ~ Paul J. Karol

Mobile Augmented Reality Assisted Chemical Education: Insights from Elements 4D ~ Shuxia Yang, Bing Mei, and Xiaoyu Yue

From the Archives: Food Dyes

This issue includes the article Cross Channel Thread-Based Microfluidic Device for Separation of Food Dyes by Chunxiu Xu, Danli Jiang, Jiayi Lin, and Longfei Cai. Food dyes have been explored in numerous ways in JCE over the years including:

A New Glow on the Chromatography of M&M Candies ~ Kurt R. Birdwhistell and Thomas G. Spence

The Quantitative Determination of Food Dyes in Powdered Drink Mixes. A High School or General Science Experiment ~ Samuella B. Sigmann and Dale E. Wheeler

Using Visible Absorption To Analyze Solutions of Kool-Aid and Candy ~ Karen E. Stevens

Candies to Dye for: Cooperative, Open-Ended Student Activities to Promote Understanding of Electrophoretic Fractionation ~ Robert D. Curtright, Randall Emry, Jonathan Wright, and John Markwell

Chemistry in the Dyeing of Eggs ~ Robert C. Mebane and Thomas R. Rybolt

Engaging Students in Real-World Chemistry through Synthesis and Confirmation of Azo Dyes via Thin Layer Chromatography To Determine the Dyes Present in Everyday Foods and Beverages ~ Kristi Tami, Anastasia Popova, and Gloria Proni

Variations on the “Blue-Bottle” Demonstration Using Food Items That Contain FD&C Blue #1 ~ Felicia A. Staiger, Joshua P. Peterson, and Dean J. Campbell

Oxone/Fe²⁺ Degradation of Food Dyes: Demonstration of Catalyst-Like Behavior and Kinetic Separation of Color ~ Ruth E. Nalliah

A Global Perspective on the History, Use, and Identification of Synthetic Food Dyes ~ Vinita Sharma, Harold T. McKone, and Peter G. Markow

Investigations of Dyes at ChemEdX:

Chemical Investigations of McCormick's Color From Nature Food Colors. Part 1: Sky Blue ~ Tom Kuntzleman

Investigations of Chemicals in Natural Food Coloring. Part 2: Berry ~ Tom Kuntzleman

Investigations of Chemicals in Natural Food Coloring. Part 3: Sunflower ~ Tom Kuntzleman

Kool-aid, Cotton, and Intermolecular Forces ~ Tom Kuntzleman

Make Connections with the Journal of Chemical Education

With 95 volumes of the Journal of Chemical Education to examine, you will always find a way to make a connection, such as exploring the articles mentioned above, and many more, in the Journal of Chemical Education. Articles that are edited and published online ahead of print (ASAP—As Soon As Publishable) are also available.

Do you have something to share? Write it up for the Journal! For some advice on becoming an author, it’s always very helpful to read Erica Jacobsen’s Commentary. In addition, numerous author resources are available on JCE’s ACS Web site, including recently updated: Author Guidelines and Document Templates. 

What percentage of your high school chemistry students will go on to a career in science? I’m pretty sure that it’s not 100%. Does that mean they shouldn’t be in a chemistry class? No. All students are part of a society that should understand at least basic chemistry and how it relates to our lives. The June 2018 Journal of Chemical Education article Developing Awareness of Professional Behaviors and Skills in the First-Year Chemistry Laboratory (available to JCE subscribers) supports the idea that there can be an additional benefit for chemistry students in the area of “soft” skills, such as being able to work in a team and to communicate well.

Although the research described in the article was carried out with first-year undergraduates in the laboratory, the skills that they investigated with ~9500 students over the space of three semesters are important to high school students as well. For example, the ability to work well with others, to be prepared and organized, and to manage one’s time well can benefit teenagers as they join the workforce in a summertime or afterschool job or begin to function in a college or trade school learning environment.

The authors point out, “Skills such as organization, communication, interpersonal skills, and self-motivation are all highly sought by employers, but students may not explicitly learn how to develop these skills until late in their degree program, if at all.” Their article highlights a potential solution, using students’ time in the laboratory to make them aware of the “qualities and behaviors of a professional scientist,” while offering an opportunity for staff assessment and student self-assessment of these skills.

It begins with staff and student training, to make sure everyone is on the same page, using their rubric below, plus discussing examples of the behavior at each level. You can see from the rubric that students were assessed and self-assessed in three major skill areas: organizational, interpersonal, and work-based, with skill subsections for each. Both staff and students rated using a four-level scale, from “not evident” up to “exemplary.” Staff included additional feedback using a selection of prewritten comments along with personalized feedback, while students were encouraged to justify their self-ratings with comments and examples. Staff did not see the student self-assessments until after entering their own feedback.

Table 1 – Reprinted with permission from Developing Awareness of Professional Behaviors and Skills in the First-Year Chemistry Laboratory, Chadwick, de la Hunty, and Baker. Journal of Chemical Education, 95 (6), pp 947 - 953. Copyright 2018 American Chemical Society.

I found the results interesting, in their change over time from the start to the end of the semester during five separate lab experiences. At the start, many students were generally either overconfident or underconfident in their skills. They seemed to link their knowledge of the content with their professional skills. If a student was not confident in chemistry knowledge, they assessed themselves as lower in professional skills, even though according to staff assessment, they displayed a higher level of the skills; those with a lot of confidence in their content knowledge tended to be overconfident of their professional skills. As the semester continued, staff and student self-evaluation came into closer agreement, with students eventually rating themselves even more critically than staff at the end of the semester. The article includes multiple examples of student and staff comments. The authors report that it served as a good motivator for student performance in these areas. Students were able to receive feedback within a short time span (48 hours), which they could then use to adjust their performance during a future lab time.

Aspects of this could be integrated into the high school chemistry lab and classroom and are likely already in use by high school educators already. Students could be brought in to a discussion, as the undergraduates were, as to what specific behaviors would signal meeting a particular level of competence. Select just a few skills to start. For example, discuss how it looks if one “used time in the lab effectively” or “was an effective member of a team” or “worked safely.” Ask them to make direct connections to how these skills would be a plus at their jobs, volunteer positions, or in other classes. Use five-minute self-assessment opportunities at the end of lab to gauge how their view of their skills matches up with yours. Are you already integrating skills like these into your lab or classroom? Share!

More from the June 2018 Issue Mary Saecker’s post JCE 95.06 June 2018 Issue Highlights categorizes the articles you’ll find in this month’s issue. The cover graphic is particularly striking, together with a description of the nanoscopic structures that are present on butterfly wings. She has also sorted through the JCE and ChemEd X archives to collect multiple articles and experiments related to food dyes.

Don’t forget you can also share what you’ve written or used from JCE at ChemEd X. Sibrina Collins, co-author with LaVetta Appleby of Black Panther, Vibranium and the Periodic Table (freely available) described their work in the ChemEd X post Connecting Black Panther’s Vibranium to the Periodic Table. Start by submitting a contribution form, explaining you’d like to contribute to the Especially JCE column. Then, put your thoughts together in a blog post. Questions? Contact us using the ChemEd X contact form.