Volume 4, Issue 1

Organonitrogen and organosulfur compounds are abundant in the natural environment. To understand the biological redox pathways properly, it is important for learners to be able to count the oxidation number of organic carbons. However, the process of counting is not always easy. In addition, organonitrogen and organosulfur molecules are seldom studied. To compensate these problems, this paper explores the bond-dividing method, which can effectively determine the mean oxidation number of carbons of organonitrogen and organosulfur molecules. This method uses the cleavage of carbon-sulfur and carbon-nitrogen bonds to obtain the organic and inorganic fragments. The mean oxidation numbers of carbon atoms, nitrogen atoms, and sulfur atoms can be calculated by the molecular formulas of their fragments. Furthermore, when comparing organosulfur or organonitrogen molecules in a redox conversion, the changes of the mean oxidation numbers of carbon atoms, nitrogen atoms, and sulfur atoms can be used as indicators to identify the redox positions and determine the number of transferred electrons.

High-resolution mass spectrometry (HRMS) has become increasingly affordable and user-friendly. Its potential spans a wide range of applications and experiments including the measurement of accurate masses, supporting the elucidation of elemental compositions and the identification of unknown compounds. To illustrate the main features of mass spectrometry, and particularly, of HRMS, we have designed and implemented a 3-h laboratory experiment using direct infusion electrospray HRMS analysis of non-steroidal anti-inflammatory drugs (e.g., ibuprofen or naproxen) solutions, acquiring full-scan spectra in both positive and negative ionization modes. The experimental accurate mass measurements ( m / z values) of selected characteristic fragment ions -so called twin ions, with common elemental composition in both ionization modes but with different charge, allow the indirect measurement of the mass of an electron with relative errors below 5% with respect to the accepted IUPAC value (0.00055 Da). The experiment demonstrates how powerful and useful HRMS can be for research challenges often encountered during undergraduate or graduate research projects as well as for addressing undergraduate level general chemistry problems that provide the opportunity to discuss aspects related to the Nature of Science in an analytical chemistry context (such as measurement precision and accuracy).

The growing interest in electrochemistry over recent years has sparked an increase in the popularity of various electrochemical techniques, including more advanced methods, that have previously been overlooked in academia and industry. This makes comprehensive hands-on experience in electrochemistry a highly demanded addition to chemistry graduates. However, many students do not receive sufficient training in the theory and experimental design to confidently use and apply various electrochemical techniques throughout their undergraduate, and sometimes even in graduate studies. Here we summarize the theory and practical applications for both rotating disk electrode (RDE) and rotating ring disk electrode (RRDE) techniques. The different modes of operation of rotating ring disk voltammetry, methodologies of data analysis and interpretation as well as the scope of the information that can be extracted from the RDE/RRDE are discussed. Proposed modifications of the laboratory curriculum will allow students to examine and learn valuable information about the reactions on the surface of the electrode/liquid interface. This information will allow chemists to confidently use RDE and RRDE techniques for a wide range of research and development targets. Furthermore, incorporating these techniques into existing chemistry laboratories will help chemistry educators to enrich the undergraduate chemistry curriculum and improve students’ learning outcomes.

Combustion reactions, stoichiometry, and redox reactions are some of the basic contents in chemistry curriculum. Although the counting of transferred electrons is critical in redox reactions, assigning mean oxidation number of organic carbons (ONc) is not always easy. Even though the relationship between the oxidative ratio (OR) and ONc is known, the relationship between the number of transferred electrons (Te − ) and OR has not been thoroughly studied. The H-atom method has already been developed to balance and deduct organic combustion reactions. It can be used further to help establish the relationships among the stoichiometric coefficients (SC), the number of transferred hydrogens (TH), and Te − . This article uses the procedures of the H-atom method for balancing and deducting, and the known relationships among SC, TH, and Te − for exploring the relationships among SC, Te − , ONc, and OR in organic combustion reactions. By integrating three sets of relationships: (i) SC and Te − , (ii) Te − and ON, and (iii) SC and OR, the interconversions among SC, Te − , ONc, and OR can be mathematically formulated. Furthermore, Te − , ONc, and OR can be assigned by SC and the general molecular formula of C x H y O z X w .

What happens at the very beginning of the titration of a weak acid or base is a question sometimes asked by undergraduate students when introduced to the concept of buffer solution. To attempt to answer this question, a simple quantitative approach is developed, which also allows explaining more general properties of the weak acid or weak base titration process, while serving as well as an introduction to the theoretical, quantitative treatment of this subject. Using this approach, it can be shown that, at the beginning of the titration, the reaction between a weak acid (base) and a strong base (acid) does not occur on a one to one ratio when very small amounts of the strong base (acid) are added.

Many high school students and first-year undergraduate students find it difficult to balance redox reactions. A method using zero oxidation number to balance redox equations is presented herein. This method may shorten the balancing time and lessen the effort. It is a helpful complement to the traditional oxidation number method and half-reaction method.

Radioactive decay is not only important in the field of radiochemistry but also useful as a teaching material for chemical kinetics. Although differential equations are often used to explain how decay rate changes over time, there are many students even in college or university who are not very good at mathematics and have difficulty in solving differential equations. Those students are expected to appreciate institutive and schematic illustrations using Excel sheets. In this paper, a water and tank model to demonstrate how radionuclides decay and decrease over time is presented as an example of the model that the students can develop or rearrange by themselves. Therefore, only four arithmetical operations were used in the sheet, so that the students can easily grasp the basic concept of a decay curve or radioactive equilibrium even if they do not have great knowledge of differential equations. In addition, only “Record Macro” and built in “Charts” were used on the sheet, and therefore, no knowledge or skill in graphic programming, such as Visual Basic, is needed to make and use the sheet. A brief online survey indicated the model was interesting to high school students. Since Excel is widely used all over the world, the sheets we have developed can be used in many countries without additional expense.

In this paper, we describe the structure, development, and validation process of customized pedagogical kits (CPKs) for differentiated instruction (DI) in chemistry. The CPKs rely on the DI approach, comprising varied pedagogical activities (e.g., games, inquiry activities, puzzles, simulations, models) designed as treatments, to help chemistry teachers personalize their teaching according to students’ misconceptions. The kits are based on the response to intervention (RTI) model, where the teacher applies an ongoing evaluation to meet the individual student’s needs within an evolutionary flexible process of learning. Each kit includes a diagnostic task, its characterization, pedagogical treatments for diagnosed misconceptions, and an assessment task, to evaluate the effectiveness of the treatments implemented in the classroom. The kits are developed along relevant literature criteria for using DI strategies and are based on constant validation and ongoing assessment, as demonstrated in the Redox-reaction CPK development. The validation and impact of the CPK on students’ achievements are supported by 25 chemistry teachers that implemented the full kit in their classrooms. Furthermore, the CPKs developed in the present research have succeeded in resolving many of the difficulties and challenges mentioned in the literature as obstructing the implementation of DI.

Social distancing measures due to the SARS-CoV-2 virus have profoundly challenged the educational experimental work. We have sought to remediate this issue by designing a series of low cost, low risk, quick, and qualitative electrochemistry and corrosion experiments to be performed in the student’s homes at the microscale with a kit provided by the teacher. One such experience is the electroplating of Sn from an aqueous chloride solution using readily available soldering wires (e.g., Sn–Pb alloy, or Sn–Ag–Cu alloy). This process catches students’ attention due to its simplicity and variety of possible applications that include corrosion protection, fabrication of electronic components, plating of cooking utensils, lithium batteries, etc.

This paper implements the 5E instructional model to reveal authentic concepts in chemistry, in particular the ambiguous oxidation state formalism of copper sulfide (CuS) for pre-service science teachers (PSTs). We discuss the process and outcomes of learning phases of the 5E (engage, explore, explain, elaborate, and evaluate) for authentic chemistry learning. The puzzle activity of engage phase demonstrate PSTs prior-knowledge, understanding, problem-solving skills in the fundamental concepts of chemistry. However, we observed misconceptions in chemistry concepts, in particular the oxidation state formalism of CuS. Next, the explore phase describe how the scientific evidence from research literature give insight into whether the PSTs conceptions are in accordance with research evidence. The research evidence from collaborative literature review revealed the uncertainty in the oxidation state formalism of CuS. In the explain phase, we explained the complex electronic structure of CuS. In the fourth phase, the elaborate phase, we involve the PSTs in the book review to elaborate and analyze the uncertain concept. The results of the book review provide insight into the coverage of oxidation state formalism of CuS in nine chemistry textbooks. Finally, in evaluate phase, the results of questionnaire describe the PSTs perspectives and experiences in the student-centered chemistry learning.