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Limonite is the field term for a mixed assemblage of ferric oxyhydroxides, often containing nonferric silicate impurities. It is abundant on Earth's surface, possesses variable iron content, and is easily recognized by distinctive yellow and ochre hues. Limonite is a unique centerpiece for undergraduate chemistry laboratories because each sample represents a true unknown to faculty and students alike, and because limonite does not digest readily with common methods. Senior students were guided through a primary literature review to assess and establish an appropriate digestion method. Students then constructed the procedure for determining the iron content in limonite using Limonite hand atomic absorption spectroscopy. A final report, produced in the samples style of this Journal, completed the start-to-finish process used by scientists, helping students learn how novel problems are solved in the laboratory. General chemistry students were provided with limonite extracts and used UV-vis spectroscopy to determine their iron contents, gaining proficiency in wet-lab, data collection, and analysis skills. Lab reports included an interdisciplinary discussion/interpretation of results from chemistry and geologic perspectives. The method used by students for digestion and iron extraction was validated using goethite and iron(III) oxide as standards (<3% error). The two spectrometric methods provided comparable results for the iron content in limonite. Despite challenging all students, these experiments were rated favorably in written evaluations, and students self-rated their learning gains as very high. Limonite experiments promote curiosity, discussion, and departure from laboratory exercises with predetermined results. Students become vested in analyzing a geologically important material that is inherently complex and heterogeneous. [ABSTRACT FROM AUTHOR]

ABSTRACT This paper presents a simple method for solving multireaction chemical equilibrium problems via Gibbs Minimization through the use of a stochastic global optimizer. The method is explained at the level of upper-undergraduate chemistry or chemical engineering students. Its matlab code is also presented and explained. Four examples with varying difficulties illustrate the versatility and robustness of the method, which is simple, general, and scalable and can be easily extended to simultaneous chemical and phase equilibrium problems. © 2016 Wiley Periodicals, Inc. Comput Appl Eng Educ 24:899-904, 2016; View this article online at ; DOI [ABSTRACT FROM AUTHOR]

Caffeine (1,3,7-trimethylxanthine) is an alkaloid stimulant that is popular in beverages. Fluorescence-coupled methods have been used to measure the caffeine content in coffee, tea, soft drinks, energy drinks, and cosmetics. In this experiment, we have developed a method for detecting caffeine in beverages utilizing the effect of the caffeine concentration on the fluorescence of acetylsalicylic acid (aspirin). Caffeine quenches the fluorescence of aspirin and the resulting Stern-Volmer plot from caffeine standard solutions can be used as a calibration curve. This method meets the criteria for fast, sensitive, and convenient caffeine detection. The caffeine concentration values in a'vitae caffeine water samples and Ale-8-One ginger ale beverage were in quantitative agreement with the reported values, within experimental error. This method can be extended to other caffeinated beverages that are clear or have an overall light color. This experiment is appropriate for the physical chemistry laboratory, the analytical chemistry laboratory, and the medicinal chemistry laboratory. Instructors may find the framework useful for teaching concepts in fluorescence spectroscopy and quenching, as well as the analysis of active ingredients in food products and cosmetics. [ABSTRACT FROM AUTHOR]

This experiment was designed and successfully introduced to complement the nanochemistry taught to undergraduate students in a useful and interesting way. Colloidal Ag nanoparticles were synthesized by a simple, room-temperature method, and the resulting suspension was then used to study the surface-enhanced Raman scattering (SERS) of methylene blue. The colloid was also characterized by UV-visible spectroscopy, and these results were used to help explain some of the observed SERS features. The students looked at the effects of concentration and acquisition time on the measured SERS spectra, and the final part of the experiment was based around using their newly acquired knowledge to investigate the lowest concentration of methylene blue that could be detected. Concentrations of 5 × 10-10 M were routinely achieved. The combination of UV-visible spectroscopy, SERS, and nanochemistry made for an interesting and thought-provoking laboratory experience. [ABSTRACT FROM AUTHOR]

In this upper-level undergraduate experiment, students utilize micro-Raman spectroscopy to characterize graphene prepared by mechanical exfoliation and chemical vapor deposition (CVD). The mechanically exfoliated samples are prepared by the students while CVD graphene can be purchased or obtained through outside sources. Owing to the intense Raman signal of a few-layer graphene on a 300 nm thermal oxide silicon wafer, students can learn how different instrumental parameters used in Raman microscopy affect the quality of the measurement. This experiment gives students a first-hand experience in the production of a two-dimensional nanomaterial and exposes them to the utility of micro-Raman spectroscopy as a characterization technique. [ABSTRACT FROM AUTHOR]

In this laboratory experiment, upper-division undergraduate chemistry and biochemistry majors investigate amide-bond-forming reactions from a green chemistry perspective. Using hydrocinnamic acid and benzylamine as reactants, students perform three types of amide-forming reactions: an acid chloride derivative route; a coupling reagent promoted method; and a boric acid catalyzed condensation. After isolation of the common product, students assess the reactions using the 12 Principles of Green Chemistry and several green chemistry metrics: atom economy; reaction mass efficiency; process mass intensity; and the EcoScale. In addition to assessing what route is the greenest, students also compare the metrics to discern what aspects of green chemistry each metric captures. In order to extend sustainability to economic considerations, the projected "front-end" cost of synthesizing a kilogram of the amide is calculated based on data from each reaction. The experimental work is conducted over two 3 h laboratory periods. [ABSTRACT FROM AUTHOR]

While structure-property relationships are commonly developed in applications of physical organic chemistry to real-world problems at the graduate level, they have not been generally emphasized in the undergraduate chemistry curriculum. For instance, the ability to modify the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) in p-conjugated small molecules and polymers is of particular interest in the fields of polymer chemistry and materials science, where small-gap systems can function as semiconductors in electronic devices. In order to demonstrate a general strategy for tuning the HOMO-LUMO energy gap for p-conjugated materials, a new experiment was designed for the undergraduate organic laboratory course that combines synthesis with theoretical calculations for p-conjugated biphenyl systems with differing electronic properties to generate a simple structure-property study of functional group substitution on the biphenyl core. The synthesis of electron-rich and electron-poor biphenyl compounds was accomplished by students with a modified procedure from the literature that uses green Suzuki conditions to yield 4'-(tert-butyl)-[1,1'-biphenyl]-4-ol (1) and methyl 4'-(tert-butyl)-[1,1'-biphenyl]-4-carboxylate (2) with average yields of ~50% and ~60%, respectively. The students characterized their products with TLC, NMR, IR, and UV-vis (from a representative sample) spectroscopies. A comparison of the UV-vis absorption spectra from density functional theory calculations and experiment showed how a p-conjugated system's HOMO-LUMO gap was tunable with structural modifications to the core, which illustrated how physical organic principles could be used to understand the electronic properties of a p-conjugated system. [ABSTRACT FROM AUTHOR]

Quantification of the many constituents that make up our food, whether they are desirable (vitamins, antioxidants, nutrients) or undesirable (pesticides, toxins), is one of the most practical applications of chemistry. In this study, kombucha, a popular fermented tea beverage, was analyzed using acid-base titration and high-performance liquid chromatography (HPLC). Kombucha is made via the fermentation of sweetened black tea with a symbiotic culture of bacteria and yeast (SCOBY), which produces acetic acid in addition to a variety of other organic acids and vitamins. The aim of this study was to analyze the acid content of kombucha over a 21-day fermentation period in order to characterize the fermentation kinetics. Titrimetric analysis revealed that the total acidity increased linearly with fermentation time at a rate of 1.5 mM/day. The acetic acid content was also quantified by HPLC at 7-day intervals by standard addition and compared to the total acidity determined by titration. A paired Student's t test was used to validate the methods. In an extension of the lab, HPLC was also used to identify and quantify the caffeine content of kombucha. The experiments utilized in this study provide a means to characterize beverages and fermentation as well as teach important quantitative and statistical skills. This study was implemented as a three-week teaching lab in a quantitative analysis course for undergraduate chemistry majors. [ABSTRACT FROM AUTHOR]

Field trips are an underutilized opportunity to provide depth and richness in college-level chemistry courses. The authors have found that a field trip, such as to the Advanced Photon Source (APS) at Argonne National Lab, greatly enhances the impact of a course in X-ray crystallography. Students who attend this field trip report that it is a highlight of the course and develop a lasting interest in the science of X-ray crystallography as a result. We report on our experience in planning these trips, advise on best practices, and demonstrate the positive impact of a field trip on student learning and engagement. [ABSTRACT FROM AUTHOR]

An approach to the creation of learning materials that aid the visualization of stereoselective reaction pathways is presented. Molecular editing software can be used to create models of various transition-state geometries. These 3-dimensional models can be manipulated, using suitable visualization software, to select relevant viewpoints. By using an overlay annotation tool, line-diagrams can be drawn directly over these 3-dimensional representations. This may help students to make representational translations between the 3-dimensional structures (transition states, etc.) and the 2-dimensional diagrams typically used to depict these objects. [ABSTRACT FROM AUTHOR]

In this article, a bomb calorimeter experiment and subsequent calculations aimed at determining the strain energy of the cyclobutane backbone are described. Students use several butanol isomers instead of the parent hydrocarbons, and they manipulate liquids instead of gases, which makes the experiment much easier to perform. Experiments show that the estimated strain energy is reasonably close to literature values for cyclobutane. [ABSTRACT FROM AUTHOR]

The enthalpy of vaporization (ΔHvap) of salt solutions is not easily measured, as a certain quantity of pure water has to be evaporated from a solution, at constant composition, and at a fixed temperature and pressure; then the corresponding heat input has to be measured. However, a simple bubble column evaporator (BCE) was used as a novel method that allowed undergraduate students to determine the ΔHvap value of a salt solution within an hour or so, because it only required temperature measurement (at a steady state) of the column solution and the inlet gas flowing into the column. In this article, by way of illustration, the ΔHvap value of a 0.5 M NaCl solution was determined using the BCE process. In this experiment the evaporative cooling effects of the column were also easily demonstrated, as the inlet air at room temperature cooled the column solution to less than 10 °C. The change that students measured directly demonstrated the endothermic process of water vaporization. The role of several basic physical chemistry concepts, such as vapor pressure, phase transition, and enthalpy, involved in this experiment can be reinforced. An unexpected property of some common salt solutions, of bubble coalescence inhibition, was also observed in this experiment. [ABSTRACT FROM AUTHOR]

Teaching materials characterization to support student research projects requires a systematic educational approach, because characterization involves a combination of analysis instruments. As analytical instruments are expensive, it is difficult to provide multiple sets simultaneously. An effective educational program allows students to select their own research materials to characterize and apply their personal strategies of instrumental analysis. These strategies are designed around the purposes of the analytical instruments, e.g., molecular structure analysis, crystal structure analysis, morphology assessment, surface analysis, elemental analysis, and thermal analysis. An open-ended laboratory complements this educational purpose. Here, we report on an open-ended laboratory program for fourth-year undergraduate and graduate students at the Materials Characterization Central Laboratory at Waseda University (Tokyo, Japan). The goals of our open-ended laboratory program are to enable students to (1) conduct instrumental analysis, (2) operate analytical instruments, and (3) interpret their data. A team led by a supervisor and laboratory staff offers students a flexible program. This flexibility can be applied to various research fields, such as macromolecular chemistry, inorganic chemistry, organic chemistry, physical chemistry, electrochemistry, physics, catalyst chemistry, biomaterials science, and chemical engineering. These diverse research fields demonstrate the feasibility of applying our open-ended laboratory program to student research projects. [ABSTRACT FROM AUTHOR]

In this work, we described an image processing procedure for the measurement of surface tension of the air-liquid interface using isothermal capillary action. The experiment, designed for an undergraduate course, is based on the analysis of a series of solutions with diverse surfactant concentrations at different ionic strengths. The objective of the work is to illustrate some concepts such as Gibbs isotherm and surface excess for the case of ionic surfactants. To perform the experiment, it is necessary to use glassware commonly found in a chemistry lab along with an USB microscope and digital image processing program (available in the public domain). The experiment can be completed in a 4 h laboratory session. [ABSTRACT FROM AUTHOR]

In this experiment for an upper-division course in organic structure determination, each student prepares an unknown compound and characterizes the product using multiple spectroscopic techniques. The unknowns, 2-arylsubstituted 1,4-dihydro-3,1-benzoxazines and 1,2,3,4-tetrahydroquinazolines, are prepared in a single step by the condensation of commercially available aryl aldehydes with 2- aminobenzyl alcohol or 2-aminobenzylamine, respectively. The products are purified by recrystallization and characterized by their mass, IR, ¹H NMR, 13C NMR, COSY, and HMQC spectra. Pre- and postlab assignments encourage students to use both mechanistic reasoning and information from multiple spectroscopic techniques for structure elucidation. [ABSTRACT FROM AUTHOR]

The development of novel, high-yielding, and selective methodologies for the asymmetric synthesis of stereocenters is at the forefront of modern synthetic chemistry research. Organocatalysis can now be viewed as a viable alternative to the use of the sometimes toxic transition-metal catalysts. In this experiment, the simple synthesis of an achiral imidazolidinone organocatalyst is described and its performance is compared to that of a related commercially available chiral catalyst in a Diels-Alder cycloaddition. The organocatalyst operated via an iminium ion intermediate and the product of the Diels-Alder cycloaddition was purified by silica plug filtration (no flash column chromatography required). The diastereoselectivity was readily measured with ¹H NMR spectroscopy and optionally, the enantioselectivity of the chiral catalyst can be assessed with chiral GC. The experiment can be performed over three laboratory sessions and is suitable for a third- or fourth-year undergraduate laboratory curriculum. The experiment demonstrated not only the synthesis of an organocatalyst but also the effect and importance of catalyst design on the stereochemical outcome of a Diels-Alder cycloaddition. [ABSTRACT FROM AUTHOR]

Introductory chemistry students often have difficulty visualizing the 3-dimensional shapes of the hydrogenic electron orbitals without the aid of physical 3D models. Unfortunately, commercially available models can be quite expensive. 3D printing offers a solution for producing models of hydrogenic orbitals. 3D printing technology is widely available, and the cost of 3D printing "inks" is relatively low. Creation of models requires graphing electron orbital probability distributions in spherical coordinates and exporting as stereolithography (.stl) files (a common format for 3D printing). There is both freeware (CalcPlot3D), and license-requiring (Matlab, Mathematica, Maple) software capable of plotting orbital equations and exporting in the required format. The process of creating the orbitals is relatively simple, and the 3D printing methodology is cost-effective. [ABSTRACT FROM AUTHOR]

The work presented here is the summary of a 3 year study that aimed to uncover how students' perception of science changes with the chance to participate in a miniconference that is incorporated into the biochemistry lecture course. Students were asked to work in groups of 2 or 3 and research a topic that is related to the material covered in class. Their research was presented during the last lecture of the course, and the presentation was conducted similar to a conference poster session. The students' grades on this assignment were entirely based on peer evaluation and not on evaluation by the instructor. A survey was conducted before and after this assignment to gauge how the experience changed students' perception of science. The study was conducted with both STEM majors and non-STEM majors to allow comparison of how these two groups of students were affected by the experience. [ABSTRACT FROM AUTHOR]

A summary of fundamental changes made to the undergraduate physical chemistry curriculum in the Chemistry Department at Gustavus Adolphus College (beginning in the 2013-2014 academic year) is presented. The yearlong sequence now consists of an introductory semester covering both quantum mechanics and thermodynamics/ kinetics, followed by a second semester that covers more advanced and integrated topics. While the initial rationale for changing the physical chemistry sequence was to improve the department's overall curriculum, the process has raised some important questions about the propriety of the traditional approach to physical chemistry education in the 21st century. [ABSTRACT FROM AUTHOR]

Chemical engineering is mostly taught using traditional classroom teaching and laboratory experiments when possible. Being a wide discipline encompassing topics such as analytical chemistry, process design, and microbiology, it may be argued that brewing of beer has many relations to chemical engineering topic-wise. This work illustrates how brewing of beer on a pilot scale system may actually cover 81% of the ECTS of the bachelor degree in Chemical Engineering and Biotechnology taught at Aalborg University, which emphasizes project organized problem based learning. This large degree of coverage, exemplified for both classroom topics and student projects leads, to the conclusion that brewing may be regarded as a comprehensive learning platform in chemical engineering. [ABSTRACT FROM AUTHOR]

Laboratory research experiences are highly impactful learning environments for undergraduate students. However, a surprising number of chemistry students do not research. These students often do not research because they lack the time, interest, opportunity, or awareness. Coursebased undergraduate research experiences can reach out to these nonresearching students by lowering the barriers to research. Classroom research opportunities typically harness undergraduate efforts to benefit faculty research. Here we introduce a research course that harnesses undergraduate efforts to benefit an outside company: a local brewery. The benefits of the course design were 3-fold. First, the course attracted students not engaged with existing research opportunities. Second, the students produced data that helped the brewery make significant business decisions. Third, the students developed personally and professionally: learning to design an experiment, to work in teams, and to enjoy science. Similar research courses with local breweries are feasible and could improve student engagement in research at other educational institutions. [ABSTRACT FROM AUTHOR]

This study describes the development and application of a three-tier test as a valid and reliable tool in diagnosing students' misconceptions regarding some basic concepts about carbohydrates. The test was administrated to students of the Pharmacy Department at the University of Bijeljina (Serb Republic). The results denoted construct and content validity of the instrument and its high reliability. Considering the results entirely, it was determined that the presence of a third tier in a task significantly affected the number of identified misconceptions and the assessment of scientific knowledge. These findings suggest that certain incorrect responses should be attributed to the lack of knowledge rather than to misconceptions, and likewise, some correct responses should be attributed to the lucky guess rather than to scientific knowledge, which implies a higher credibility of the results obtained. In this study, several misconceptions about carbohydrates were revealed. As there are only a few studies examining students' misconceptions in chemistry using three-tier tests available in literature, future research should focus on the further implementation of three-tier tests as a powerful tool for simple detection of misconceptions. [ABSTRACT FROM AUTHOR]

Encouraging students to participate in collaborative discourse allows students to constructively engage one another, share ideas, develop joint understanding of the course content, and practice making scientific arguments. Argumentation is an important skill for students to learn, but students need to be given the opportunity in class to engage in argumentation. To investigate the importance of instructor facilitation on argumentation, two iterations of one instructor's Process Oriented Guided Inquiry Learning (POGIL) physical chemistry course were studied using the Toulmin analysis and the inquiry-oriented discursive moves frameworks. Data were collected by recording class conversations and interactions taking place in the POGIL classrooms. Initial analysis of an individual instructor's implementation of the POGIL materials provided data regarding the nature of small group and whole class interactions and the nature and quality of student-generated arguments. The instructor was then able to make modifications to the facilitation of that course for the next iteration of the course. Data were collected for this subsequent implementation, and the two sets of implementations were compared. It was found that slight changes in facilitation can lead to significant differences in the types of student interactions and the nature of students' arguments. Simultaneous reporting was useful in encouraging iterative argumentation and discussion among students, and setting expectations that students must be ready to explain how they solved the problem and justify their work helped students develop their argumentation skills. [ABSTRACT FROM AUTHOR]

Safety education is absent in the chemistry curriculum. This commentary discusses the consequences of the missing safety education for graduates and institutions that hire them. It suggests and discusses the application of the theory of Normalization of Deviance to explain why safety education is missing. It suggests ways to fix the shortcoming by involving not only chemistry but other departments and top administrators. It suggests ways to incorporate safety education, the "why" of safety, into the curriculum. [ABSTRACT FROM AUTHOR]

A series of undergraduate laboratory experiments that utilize reversed-phase HPLC separation, inductively coupled plasma spectroscopy (ICP), and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) are described for the analysis of commercial sunscreens. The active ingredients of many sunscreen brands include zinc or titanium oxide in addition to organic acids. Students determine the zinc content using ICP, and the chemical composition as well as particle sizes using SEM-EDS. The organic UV absorbers octocrylene and oxybenzone are quantified using HPLC. With the incorporation of these interesting characterization techniques in second or fourth-year chemistry courses, and by having students analyze sunscreen samples that are medically relevant in terms of health effects, students engage in timely research and at the same time gain exposure to a variety of instruments in the analysis of a familiar household product. [ABSTRACT FROM AUTHOR]

Modifications of the classical blue bottle experiment, air oxidation of glucose catalyzed by methylene blue under alkaline conditions, were investigated. Following the green chemistry formulation proposed by Wellman and Noble, we studied the visual behaviors of air oxidation of vitamin C catalyzed by redox indicators. New formulations for the chemical traffic light and vanishing valentine experiments are presented in this paper. We also report, for the first time, chemical pattern formation in this oxidation reaction of ascorbic acid. These results open many possibilities for laboratory practicals as well as demonstration activities. [ABSTRACT FROM AUTHOR]

Air oxidation of reducing sugar under alkaline conditions and air oxidation of ascorbic acid catalyzed by methylene blue are known as the classical and the green chemistry versions of the blue bottle experiment, respectively. We propose a faster alternative of the blue bottle experiment in which air oxidation of benzoin under an alkaline condition is the main reaction. In addition to methylene blue (for the blue bottle experiment), erioglaucine (FD&C Blue #1), indigo carmine (FD&C Blue #2, for the chemical traffic light experiment), resazurin (for the vanishing valentine experiment), safranine, phenanthrenequinone, and tetrazolium chloride also catalyze the autoxidation of benzoin. Similar to sugar/hydroxide and ascorbic acid/CuCl2 chemical pattern formations are observed in this benzoin/hydroxide system. Our colorful reactions and patterns open the possibilities for both pedagogical activities and future in-depth research. [ABSTRACT FROM AUTHOR]

A simple, microscale experiment was developed with the aim of demonstrating the concept of umpolung in synthetic organic chemistry. Starting from a common alkyl sulfinate, students perform a polarity inversion by performing a Grignard-based sulfoxide synthesis and a Mannich-type formamide synthesis. The products are purified without chromatography and are easily characterized. Procedural optimization established an experiment time of less than 3 h. Spectroscopic characterization includes the interpretation of ¹H NMR, 13C NMR, and FTIR spectra. This experiment, therefore, is suitable for a mid- to upper-level undergraduate organic lab curricula for illustrating advanced synthetic methods. [ABSTRACT FROM AUTHOR]

A discovery-based Grignard experiment that emphasizes several important concepts in organic chemistry is reported. The Grignard reagent from 1- bromo-4-chlorobenzene was prepared and reacted with dimethylformamide (DMF) to synthesize 4-chlorobenzaldehyde. Students were tasked with predicting halogen reactivity in the formation of the Grignard reagent, predicting the final product, and drawing a reasonable mechanism for the reaction with DMF. The Grignard reaction with tertiary amides is typically not discussed in the organic chemistry curriculum, so the students have an opportunity to apply concepts covered in lecture to a new situation. Lastly, the students experimentally verified the identity of the product using thin layer chromatography, melting point analysis, gas chromatography, IR and NMR spectroscopy, and mass spectrometry. [ABSTRACT FROM AUTHOR]

We present a novel guided inquiry second semester organic chemistry laboratory rearrangement experiment. Students performed the Favorskii Rearrangement to obtain methyl cyclopentanecarboxylate in good yields. The students learned about the individual steps of the Favorskii mechanism and were required to propose a complete reaction mechanism and product structure. The students then confirmed the structure of the product by NMR and IR spectroscopy. This experiment provides students with experience in running organic chemistry reactions, structure determination, spectroscopy, general problem solving, and drawing rearrangement mechanisms. [ABSTRACT FROM AUTHOR]

A two-session experiment is designed to introduce undergraduate students to concepts in catalysis, transition metal complexes, polymer synthesis, and postpolymerization modifications. In the first session, students synthesize poly(glycidyl methacrylate) via low-catalystconcentration atom transfer radical polymerization (ATRP). The lowcatalyst- concentration technique simplifies the experimental setup, reduces the cost of the synthesis, eliminates the need for catalyst removal from the product, and thus ultimately makes ATRP an environmentally benign process. In the second session, students modify the well-defined epoxidecontaining polymers with nicotinamide in the presence of acetone, to afford fluorescent polymers. [ABSTRACT FROM AUTHOR]

Nanoscience and nanotechnology have reached the syllabi of many upper-division undergraduate and masterlevel courses all over the world. There is therefore a growing need for practical exercises that illustrate the fabrication, characterization, properties, and applications of nanomaterials. Here we describe an advanced-level laboratory experiment in which students had the opportunity to fabricate surfaces modified by ordered monolayers and nanostructured materials. The surface modification was quantified by means of a quartz crystal microbalance, while the electrochemical properties of the nanoarchitectures were assessed using cyclic voltammetry experiments. Electron transfer across self-assembled monolayers mediated by gold nanoparticles was presented as a topic for discussion, and consideration of potential practical applications of the observed phenomena (catalytic and electrocatalytic processes, as well as development of optical, (opto)electronic, and photovoltaic devices with enhanced properties) was proposed as a further reading exercise. [ABSTRACT FROM AUTHOR]

Following our previous work on introducing a database of tested chemical examples from Organic Syntheses that can be used as a repository for problem set development in green chemistry courses, in this paper we extend this idea to include over 1300 examples taken from Inorganic Syntheses covering 36 volumes. Examples are sorted according to the following 13 categories: asymmetric syntheses, syntheses involving catalyst preparation, chemoenzymatic reactions, classical resolutions, convergent synthesis plans, kinetic resolutions; multicomponent reactions, multistep linear synthesis plans, natural feedstocks as starting materials, reactions involving product distributions, reactions involving sacrificial reagents, reactions involving nonunity stoichiometric coefficients, and polymerization reactions. In this paper, we highlight the skill of balancing chemical equations as a mandatory prerequisite of green metrics analysis. Through a problem set containing 70 exercises, we selected challenging examples from Inorganic Syntheses to emphasize this point and link it to the understanding of reaction mechanisms. A number of these examples also contain errors or missing information that students are asked to correct. This is yet another good training ground to exercise their skills in problem solving. [ABSTRACT FROM AUTHOR]

Cyclic voltammetry (CV) is a popular technique for the determination of electrochemical mechanisms because it can provide useful information on a redox couple. Computer simulations of CV data are sometimes used to study complex redox systems with interrelated processes. The following communication outlines an expanded version of an experiment developed to introduce undergraduate students to CV and electrochemical simulations. A new solvent/electrolyte system of dimethylformamide with 0.1 M tetrabutylammonium hexafluorophosphate increases analyte solubility, improves sample conductivity, and extends the electrochemical domain as compared to the original experiment. Simulation parameters determined by wave clipping the first redox couple of a series are used to simulate a more complex two-redox system of the same compound. Experiments designed to teach CV and electrochemical simulations to undergraduate students rarely use wave clipping as a technique to simplify experimental data for the analysis of a more complex system. The addition of wave clipping and the analysis of a two redox system increase the laboratory experience gained by the students as compared to the original experiment, which was limited to a single redox couple. [ABSTRACT FROM AUTHOR]

A student laboratory experiment to investigate the intrinsic and extrinsic bandgaps, dopant materials, and diode design in light-emitting diodes (LEDs) is presented. The LED intrinsic bandgap is determined by passing a small constant current through the diode and recording the junction voltage variation with temperature. A second visible wavelength emission method is used to determine the active bandgap for comparative purposes. The active bandgap data is used along with literature values to interpolate the ratio of elemental dopant atoms in the LED semiconductor. This work also discusses the fundamentals of bandgap theory, LEDs, and diode design and how these experimental measurements correlate to the diode structure and dopant material used to manipulate the bandgap energy and observed emission profile. Suggested questions are provided in the supplemental materials to help students further explore and understand the topic. While this laboratory experiment was created for upper level undergraduates, it can be revised and simplified for use in high school and introductory level undergraduate courses. [ABSTRACT FROM AUTHOR]

The laboratory unit demonstrates a projectbased approach to teaching physical chemistry laboratory where upper-division undergraduates carry out a transientabsorption experiment investigating the kinetics of cis-trans isomerization of N,N-dimethyl-4,4'-azodianiline. Students participate in modification of a standard flash-photolysis spectrometer by adding a temperature-controlled sample holder. The sample holder design is open-source and can be reproduced with the 3D-printing technology. Students build the experimental setup, perform the transient spectroscopy experiment, and analyze the obtained kinetics data to estimate the activation energy, enthalpy, entropy, and Gibbs free energy of cis-trans isomerization of N,N-dimethyl-4,4'-azodianiline. [ABSTRACT FROM AUTHOR]

An undergraduate electrical conductivity measurement experiment in a physical chemistry lab and basic fitting procedures are presented that allow a characterization of micellar system of hexadecyltrimethylammonium bromide (cetyltrimethylammonium bromide, CTAB) in binary mixture of water and acetonitrile (ACN) as a cosolvent (10%, v/v) at 30.0 °C. Conductivity-concentration data were processed by inbuilt function of ORIGIN software to attain the values of critical micelle concentration by method of integration. Acquiring the data-fitting skills that are developed through the addition of a computational tool to a conventional electrical conductometry experiment has a general significance for its applications to more complex upper-level experiments with the aim to process data and perform fast calculations and graphics. [ABSTRACT FROM AUTHOR]

A lab appropriate to introduce voltammetric techniques and basic electrochemical parameters is described in this work. It is suitable to study theoretical concepts of electrochemistry in an applied way for analytical undergraduate courses. Two electroactive species, hexaammineruthenium and dopamine, are used as simple redox systems. Screen-printed electrodes are used in order to allow the students to focus on the electrochemistry and avoid tedious instrumentation preparation. The analytical determination of the species studied with sensitive techniques such as differential-pulse or squarewave voltammetry is also performed. [ABSTRACT FROM AUTHOR]

A laboratory exercise for the education of students about thermal runaway reactions based on the reaction between aluminum and hydrochloric acid as a model reaction is proposed. In the introductory part of the exercise, the induction period and subsequent thermal runaway behavior are evaluated via a simple observation of hydrogen gas evolution and measurement of the temperature, which also provide basic information on the mechanistic features of the thermal runaway reaction. The exercise also includes PC aided thermometric measurements of the reaction and kinetic analysis of the induction period. The initiation time of the thermal runaway behavior under certain reaction conditions is calculated using the kinetic parameters determined experimentally by the students. The laboratory exercise provides a fundamental understanding of the mechanistic features of a thermal runaway reaction, recognition of the need for adopting safety measures when performing chemical reactions, and experience of using kinetic analysis for safety assessment. [ABSTRACT FROM AUTHOR]

A low-cost and portable colorimeter was constructed featuring a low-voltage programmable color light sensor-tofrequency converter, a CMOS 8-bit microcontroller, and an LCD display. The instrument has successfully facilitated the introduction and application of spectroscopy to groups of middle school, high school, and undergraduate students. A series of tried and tested laboratory experiments that demonstrate the utility and capabilities of the colorimeter have been developed. These laboratories not only help characterize the colorimeter but also feature challenging problems that allow students to realize the limitations of analytical instruments. The accompanying laboratories enable students to determine the concentration of a mixture of food dyes using simultaneous equations, quantify inorganic phosphate in various aqueous-based agricultural samples, calculate the concentration of salicylic acid in facial acne medication, and elucidate the stoichiometry of an iron salicylate reaction. [ABSTRACT FROM AUTHOR]

Chemistry laboratories play an essential role in the education of undergraduate Science, Technology, Engineering, and Mathematics (STEM) and non-STEM students. The extent of student learning in any educational environment depends largely on the effectiveness of the instructors. In chemistry laboratories at large universities, the instructors of record are typically graduate or undergraduate teaching assistants (TAs). Despite the importance of their role in the education of undergraduate students, TAs' instructional practices have been largely understudied outside specific reform efforts. In this study, we developed a segmented observation protocol, the Laboratory Observation Protocol for Undergraduate STEM (LOPUS), in order to characterize TAs' instructional styles in a General Chemistry laboratory curriculum. LOPUS captures both students' and TAs' behaviors every 2 min as well as initiators of verbal interactions and the nature of these verbal interactions (e.g., data analysis, explanation of concepts). Analyses of 19 videos collected from 15 TAs resulted in the identification of four instructional styles: the waiters, the busy bees, the observers, and the guides on-the-side. We found that students' behaviors were independent of these styles and limited to performing the laboratory activities, initiating conversation with TAs, and asking TAs questions. Interestingly, students rather than TAs were initiators of most verbal interactions, regardless of TAs' instructional styles. Finally, we found that the nature of TA-student verbal interactions was related to the nature of the laboratory activity (e.g., only following step-by-step instructions versus carrying out extensive data analysis). Implications of these findings for future research investigations and TA training are discussed. [ABSTRACT FROM AUTHOR]

A 1 h classroom activity is presented, aimed at consolidating the concepts of microstates and Russell-Saunders energy terms in transition metal atoms and coordination complexes. The unconventional approach, based on logic and intuition rather than rigorous mathematics, is designed to stimulate discussion and enhance familiarity with quantum numbers in classes of chemistry undergraduate students. [ABSTRACT FROM AUTHOR]

In this experiment, the students explore the synthesis of a crystalline solid-state material, barium zirconate (BaZrO3) by two different synthetic methods: (a) the wet chemical method using BaCl2·2H2O and ZrOCl2·8H2O as the precursors, and (b) the solid-state reaction from BaCO3 and ZrO2. BaZrO3 adopts a perovskite structure with a cubic unit cell. The intermediate and the products are examined by various characterization techniques. The identity and the purity of the products are determined by powder X-ray diffraction technique. The structural information on the products is analyzed by the XRD patterns, where students apply the sin2θ-ratio method to determine the type and dimension of the unit cell. The composition of the Ba2+ and Zr4+ ions in the product is determined by the gravimetric analysis, while the vibrational modes of the product are observed by Infrared Spectroscopy. [ABSTRACT FROM AUTHOR]

An approach to create an interactive and inexpensive electronic book (eBook) for an undergraduate biochemistry laboratory course is presented. This approach featured the involvement of an undergraduate student in the lead role of designing and developing the eBook using Apple's iBooks Author application. The eBook, entitled Introduction to Biochemical Methods, contains original, interactive course content, including laboratory protocols, lecture slides, images, videos, figures, and quizzes. Access to the book content was expanded through the creation of a Web-based version of the book. User access analytics on both the eBook and the Web site, along with student survey data related to the usage of and attitudes toward the eBook, also are presented. Although the Introduction to Biochemical Methods eBook was developed specifically for use in a particular course, adaptation of its content for use in other classrooms is invited, and educators are encouraged to adopt a similar approach (i.e., involving their students) in developing eBooks for courses at their learning institutions. The immersive nature of the design and development process provided significant learning experiences for the student who led the development of the eBook. [ABSTRACT FROM AUTHOR]

In a course on chemical applications of symmetry and group theory, students learn to use several useful tools (like character tables, projection operators, and correlation tables), but in the process of learning the mathematical details, they often miss the conceptual big picture about "why" and "how" symmetry leads to the quite dramatic consequences that it does. This pedagogical gap is addressed in this paper by using one of the simplest chemical model systems, the particle in a box, along with a simple symmetry operator, parity, to get a clear understanding of the consequences of symmetry. The analysis of the particle-in-a-box model is extended by analogy to molecules, and connections are made to chemically important concepts like symmetry labels of molecular states, spectroscopic selection rules, and symmetry adapted linear combinations of orbitals. [ABSTRACT FROM AUTHOR]

A laboratory project for the upper-division physical chemistry laboratory is described, and it combines IR and Raman spectroscopies with Gaussian electronic structure calculations to determine the structure of the oxalate anion in solid alkali oxalates and in aqueous solution. The oxalate anion has two limiting structures whose vibrational spectra have distinct differences: planar with D2h symmetry and nonplanar with D2d symmetry. In the former case, the IR and Raman spectra are complementary. Students measure the IR and Raman spectra of solid Na2C2O4, K2C2O4, and Cs2C2O4, and a nearly saturated aqueous solution of K2C2O4. They also carry out Gaussian calculations on the oxalate anion to predict the vibrational wavenumbers of both the planar and nonplanar structures and use the results to assign the spectra. By considering their results for the four samples, they decide on the oxalate structure in each and defend their choice in a report. The complexity of the project immerses the students in vibrational spectroscopy so that they learn the subject at a deeper level. [ABSTRACT FROM AUTHOR]

The method of least squares (LS) yields exact solutions for the adjustable parameters when the number of data values n equals the number of parameters p. This holds also when the fit model consists of m different equations and m = p, which means that LS algorithms can be used to obtain solutions to systems of equations. In particular, nonlinear LS solves systems of nonlinear equations. An important example in chemistry is the case of reagents whose concentrations are coupled through multiple equilibrium relations. The capability of nonlinear LS in this application is examined for three programming environments, Excel Solver, FORTRAN, and KaleidaGraph, on a number of equilibrium problems having up to 10 unknown concentrations. FORTRAN and KaleidaGraph perform well in all the examples, but Solver presents difficulties that render it inadequate in several cases unless the problem is reformulated in terms of a smaller number of adjustable concentrations. When the input quantities (equilibrium constants, prepared concentrations) have uncertainty, the calculations can also be used to propagate these uncertainties into the derived quantities. [ABSTRACT FROM AUTHOR]

Hydrogen bonds are very important chemical structures that are responsible for many unique and important properties of solvents, such as the solvation power of water. These distinctive features are directly related to the stabilization energy conferred by hydrogen bonds to the solvent. Thus, the characterization of hydrogen bond energetics has been vital for many areas of science. We present a laboratory experiment for physical chemistry in which the hydrogen bond energetics between methyl acetate and water is investigated by Fourier transform infrared spectroscopy (FTIR). The experiment consists of measuring the temperature dependent IR spectra of methyl acetate to determine the changes in the enthalpy and entropy of making/breaking hydrogen bonds. This experiment aims at providing the students with hands-on experience in the following topics: solution and sample cell preparation, IR spectra collection and analysis, and data modeling and thermodynamic calculations. The overall objective of this experiment is to familiarize chemistry students with a methodology used to extract meaningful and up-to-date physical chemistry properties from real experimental data. [ABSTRACT FROM AUTHOR]

This biochemistry laboratory course was designed to provide significant learning experiences to expose students to different ways of succeeding as scientists in academia and foster development and improvement of their potential and competency as the next generation of investigators. To meet these goals, the laboratory course employs three different practices that support an 'Integrated Course Design' approach: (1) incorporating basic laboratory techniques with faculty research projects, (2) promoting team-based learning, and (3) developing, de novo, a mini-NIH grant proposal that serves as a capstone project. On course evaluations, students give the biochemistry laboratory course the highest ratings for course and teaching effectiveness, and these ratings are a higher percentage overall compared to similar chemistry laboratory courses offered in the program. Students also state that the practices of the laboratory course went beyond their prior experiences in traditional lab courses. They have reported that they were excited to be involved in current research, were intellectually challenged to think in new ways, were impressed by the work accomplished with their teams, were encouraged by the growth in understanding and ability to formulate new questions, and better realized the impact of chemistry on numerous aspects of human health and everyday life. Thus, the biochemistry laboratory course experience has positively affected student satisfaction in the chemistry program, as well as student self-efficacy. [ABSTRACT FROM AUTHOR]

Laboratory experiments that demonstrate the effect of paramagnetic complexes on chemical shifts and relaxation times of protons are a useful way to introduce magnetic resonance spectroscopy (MRS) probes or magnetic resonance imaging (MRI) contrast agents. In this undergraduate inorganic chemistry experiment, a paramagnetic Co(II) cage complex is prepared by reduction of a classical Co(III) cage complex. The Co(II) cage behaves as a paramagnetic shift agent (paraSHIFT) and produces relatively sharp and highly dispersed proton resonances. Comparison of the proton NMR spectra of the diamagnetic and paramagnetic cage complexes provides opportunities for students to consider coordination complex symmetry and the effect of unpaired electrons on the chemical shifts of proton resonances. Oxidation and spin state changes of transition metal complexes, Co(III)/Co(II), are also illustrated in this experiment. [ABSTRACT FROM AUTHOR]