Search

The goals of the study were as follows: i) to design an active science learning activity on stoichiometry for grade 10 students, ii) to evaluate the academic achievement of grade 10 students after receiving an active science learning activity on stoichiometry, and iii) to investigate the perspectives of grade 10 students regarding an active science learning activity on stoichiometry. The research utilized a sample group consisting of 41 students who were enrolled in the tenth grade during the second semester of the academic year 2022. The research tools provided participants with active science learning lessons. A test of the kids' academic prowess as well as their thoughts on the use of hands-on scientific learning activities will be administered. The mean, the standard deviation, and a one-sample t-test were the types of statistics that were utilized in the investigation. The following is an outline of what the research found: i) the appropriateness of the active science learning activities was judged to be the highest level, ii) the academic achievement of grade 10 students after receiving the active science learning activities on stoichiometry had an average score that was higher than the criteria of 70% with a statistical significance at the .05 level; and iii) the opinions of students on the implementation of active science learning activities on stoichiometry were in the agree level.

The study aimed to investigate the effect of computer simulation and animation-integrated instruction on preservice science teacher trainees' conceptual understanding and retention of acid-base chemistry and stoichiometry. A quantitative approach with a pretest-posttest-delayed test quasi-experimental design was used. In the study area, there were only two sections of first-year trainees in the natural science department. So a comprehensive sampling technique of the two intact sections was employed. The two intact classes were randomly assigned to an intervention group (IG) and a comparison group (CG). Data was collected using Acid-Base Chemistry and Stoichiometry Conceptual Understanding of a two-tier multiple-choice Test (ABSCUT). Parametric statistics (independent sample t-test and ANCOVA) were used for the data analysis. The independent sample t-test was used for the pre-test analysis to examine the prerequisite experiences of trainees in the two groups and male and female trainees in the IG before the intervention. The result showed no significant difference between the mean score of the CG and IG. The result also showed no significant difference in the mean score of male and female trainees in the IG. The ANCOVA was used for post-test and delayed test analysis after the intervention. The result indicated that there was a statistically significant difference between the two groups on conceptual understanding, F(1,49)=5.07, p=0.029, partial eta squared=0.094, in favor of IG. This tends to imply the concepts of the trainees who received the intervention outperformed the comparison group. The ANCOVA result also indicated that gender difference has no statistically significant difference in the IG, F(1,24)=3.68, p=0.067. The delayed-test analysis showed that the IG has higher retention than the CG. Based on the results, this study recommended that policymakers, chemistry curriculum experts, chemistry curricular material developers, and practitioners alike consider the application of computer simulation-integrated chemistry instruction to enhance learners' conceptual understanding and retention.

Presenters' pedagogical choices are strongly affected by whether they view knowledge as coherent or fragmented. This mixed-methods survey study seeks to contribute to epistemological discussions and associated pedagogical suggestions in the context of mole ratio related mistakes evident in stoichiometry calculations performed by in-service teachers in a developing world country. Physical sciences teachers in South Africa were asked to solve four stoichiometry calculation questions, and their written solutions (361 sets) were analyzed for consistency of various types of mole ratio related mistakes. The study found high levels of inconsistencies in each observed mistake, supporting the view that most participants' knowledge lay closer to the fragmented end of the coherent-fragmented epistemological continuum. Evidence is presented for differential cognitive load, overgeneralization, and intuitive heuristics as possible explanations for these mistakes. Pedagogical suggestions are made for addressing such errors in in-service chemistry teacher workshops about stoichiometry calculations, although these may only be applicable where teacher subject matter knowledge tends to be low, such as within the developing world.

Anaerobic digestion is a complex biochemical process that is represented by the stoichiometric Buswell's equation. Buswell's equation is the study of the interface among biochemistry, mathematics, and chemistry. Students often have difficulty in understanding the nature of biochemical stoichiometry. Buswell's equation is significant for the calculation of the quantity of biomethane. Although the general formula CxHyOz of organic pure substance or mixture has been well studied, the Buswell's equation for biomolecules containing phosphorous has rarely been explored. The aim of this article is to study the nature of Buswell's equation using the H-atom method. The new general Buswell's equation, which contains phosphorous, is deduced from the H-atom and algebraic methods.

The paper presents the design and evaluation of a voluntary online introductory stoichiometry (VOIS) course aimed at facilitating the transition from secondary to higher education. The course utilized simple analogies and adaptive feedback through a formative scaffolding assessment. The study assessed the effectiveness of the VOIS course through pre- and post-knowledge tests, analysis of students' performance in general chemistry, and course evaluation surveys conducted at a Latin American University between 2019 and 2021. A total of 3,995 first-year STEM students enrolled in the course voluntarily, and 358 students successfully completed it. The results showed a statistically significant improvement in stoichiometry-related knowledge, with the pre-post test scores increasing from 4.61 to 6.55 out of 10. The matched sample analysis, which only included students with 100% participation, demonstrated a statistically significant improvement in stoichiometry and related knowledge from 5.31 to 6.61. Furthermore, an analysis comparing the performance of students who completed the VOIS course with those who didn't reveal that the former group outperformed the latter by an average of 10.6 points in the general chemistry course. This statistically significant difference exhibited a large effect size (d = 0.8). In addition, a matching technique was employed to construct a synthetic control group in order to reduce bias in the quasi-experimental design. A successful propensity score analysis was conducted, controlling for variables such as gender, grade in high school, scores in the national test, and student ranking in their high school. The results of this analysis showed a statistically significant improvement of 8.6 points in the general chemistry performance for students who completed the VOIS course compared to those who did not enroll in the course. Furthermore, the feedback from 129 respondents indicated that 80% of the students either liked the VOIS course or liked it very much, with an overall satisfaction rating of 3.1 on a four-point scale. In conclusion, the VOIS course demonstrated positive outcomes in terms of enhanced stoichiometry knowledge, academic performance, and student satisfaction. These findings highlight the potential of online courses like VOIS in facilitating the transition to higher education.

Learners underperform in stoichiometry as they lack conceptual reasoning of the underlying concepts and the ability to solve stoichiometric problems. Therefore, it was necessary to determine if there is a statistical correlation between problem-solving skills and conceptual reasoning in stoichiometry and if so, whether one can significantly predict the other. The theoretical framework is the cognitive load theory (CLT). This theory expects teachers to know where to focus their teaching and how to assess their learners' work to avoid unnecessary overloading of the working memory, which might affect their performance. The explanatory sequential mixed-method research design was employed with 410 grade 11 Physical Science learners in their intact classes. The participants wrote the learner achievement test (LAT) and responded to a semi-structured interview. The learners' test scores were then used to run a statistical test. The Pearson correlation and regression showed that the justifications given by learners for choosing correct or incorrect multiple-choice options were not due to chance, and the results of the learner interviews supported the learners' performance in the test. Moreover, the findings indicated that there was a positive correlation between problem-solving skills and conceptual reasoning where statistically, conceptual reasoning predicted learners' problem-solving skills using regression analysis.

The pharmacologically active lignans sesamin and sesamolin are minor components of sesame oil and ingredients in OTC dietary supplement capsules. We report an introductory undergraduate organic laboratory experiment combining natural product isolation and spectral analysis in which students isolate a mixture of sesamin and sesamolin by either (1) dry column vacuum chromatography (a convenient alternative to flash column chromatography) of commercial sesame oil using an apparatus constructed from common laboratory glassware or by (2) solid-liquid extraction of commercial sesame seed lignan dietary supplement capsules. Two recrystallizations from methanol remove most of the sesamolin to afford crystalline sesamin, which, due to its 2-fold rotational symmetry, students can easily identify and characterize by NMR. During a second laboratory period, students perform a 5 min, test tube-scale reaction of sesamin with catalytic BF[subscript 3]:OEt[subscript 2] to promote its epimerization to episesamin, a diastereomer of sesamin lacking rotational symmetry, and the sesamin/episesamin ratio in the resulting product mixture is established by [superscript 1]H NMR integration. Students are asked to propose a mechanism for this epimerization based on their knowledge of the reactivity of benzyl ethers under acidic conditions.

High school students and students in the first years of college have difficulties in understanding the topic of stoichiometry and, in particular, the concept of limiting reactant. Proposals aimed at overcoming these learning obstacles tend to focus on analogies, and there are few sequences that approach teaching from an experimental perspective. Those that do it usually involve specific reactions whose reagents are not easily obtained or require special equipment. In this article, an experimental activity was designed to introduce the concept of limiting reactant with nonhazardous, inexpensive, and readily available materials in combination with an innovative visual and graphic representational approach. It was implemented with three groups of 16-17 years old students (N = 74) with some previous knowledge (acid and base reactions, indicators, and slight experience in handling laboratory material). From their own observations and reasoning and without the need to go through analogical mediation, it was possible to satisfactorily arrive at the concept of limiting reactant. Subsequently, the proposal was adapted for students with no prior knowledge, and it was implemented with three groups of 9-12-year-olds (N = 27) in an informal teaching environment with similar results. This intervention could potentially help high school students better understand the concept of limiting reagents and overcome future learning obstacles in relation to other chemical phenomena that rely on this concept.

The purpose of this randomized experimental study is to apply two socio-cognitive models to understand possible ways to improve students' learning outcomes in an online introductory chemistry learning environment. Specifically, the social presence theory suggested that students' sense of relatedness and learning motivation can be increased by a real or imagined interaction with others. On the other hand, self-regulated learning theory and self-determination theory both suggested that students learn best when they direct their focus to self, rather than others. Using these two theoretical perspectives as the basis, two experimental conditions (social presence vs. self-regulated) were developed in the context of chemistry learning. Participants of the study were randomly assigned to one of the experimental conditions. Both groups were presented with a pre-test, an online micro-lecture on balancing equations, i.e., a subtopic of stoichiometry, and a post-test. Linear mixed model analysis revealed that participants in the self-regulated learning condition had higher improvement in quiz scores than had participants in the social presence condition. Implications of the study and future directions were discussed.

This study explored the perceptions of teachers and learners regarding the use of Process Oriented Guided Learning Inquiry Learning (POGIL) to teach stoichiometry. A qualitative case study was carried out at two conveniently and purposively sampled township schools in Pretoria, South Africa. For this purpose, two Grade 11 physical sciences classes were identified where 48 learners and their respective teachers, who had previously been trained to teach using POGIL, gave consent to participate in the study. Data were collected using lesson observations, focus group interviews for learners and interviews for teachers. All data were transcribed and analysed with the aid of ATLAS.ti software for qualitative data analysis. The findings from the observations indicate that the learners were excited, motivated, and actively engaged in their work. They assisted one another by attempting to answer questions supported with justification. The findings from the focus group interviews indicate that the learners were excited to learn using POGIL and wished to use the method in other subjects, including mathematics. The learners had noticed improvements in their grades and understanding of abstract topics. The findings from the teacher interviews indicated that they appreciated POGIL because they found it useful in reducing misconceptions, increasing learner participation, increasing understanding and achievement, and that their learners were more engaged. The results indicate that POGIL increased learners' interest, participation and active learning, while seemingly also improving the learners' understanding of and achievement in abstract topics like stoichiometry. POGIL may be useful in increasing active learning and participation of learners which may lead to increased understanding and achievement.

The aim of this qualitative case study was to explore secondary students' ability to transfer among representation levels in relation to stoichiometry. In the study, 40 students in the 11th grade from two classes of an Anatolian high school in the east part of Turkey were selected as sample group. The data were collected by using a questionnaire consists of ten questions designed specifically target the transformation from macroscopic to symbolic, from symbolic to submicroscopic, and from submicroscopic to symbolic level. The analysis of the data was carried out both deductively and inductively by content analysis method. The results indicate that many students were unable to establish an appropriate link among chemical representation levels regarding stoichiometry.

The basic knowledge of chemical formula writing is fundamental for chemistry students, yet many still struggle to learn it. To provide a more interactive and engaging approach that facilitates and reinforces student understanding of chemical formulas and stoichiometry of chemical reactions, we have designed a chemical jigsaw puzzle. Only eight general jigsaw puzzle shapes are needed to represent atoms (e.g., H, C, N, O, X, ···) or groups (e.g., -CH[subscript 3], Et, But, Ph, ···), shared electrons in covalent bonds, lone pairs, and unpaired electrons for radical compounds. The complementarity of the chemical jigsaw puzzle pieces can present a large variety of molecular arrangements with several functional groups, including radical and ionic species. Thus, concepts such as organic functions, resonance, hybridization, Lewis dot structures, octet configuration, formal charges, stoichiometry, and others can be readily exemplified. Its use is intended for introductory chemistry courses, especially in high school. The usefulness and effectiveness of this chemical jigsaw puzzle was checked in the classroom throughout a hands-on learning activity using medium-sized pieces, built with low-cost material.

This article presents and discusses the results of an educational innovation that seeks to introduce the world of molecular gastronomy in chemistry lessons as a means to review stoichiometry and offer an alternative way to learn. In the literature to date, there is no evidence of haute cuisine having been employed to contextualize stoichiometry problem statements with its everyday applications. The proposed novel strategy, called "MasterChemist", involved the participation of Spanish first-year university students taking the subject General Chemistry in the Bachelor's Degree in Chemical Engineering. A Game-Based Learning (GBL) approach was used to solve the exercises and make the activity more appealing and interesting by adding fun to the learning process. The problems were contextualized in the use of siphons, isomalt sugar, and the spherification technique. Furthermore, dividing students into groups also boosted their cooperative skills. The students' answers to a final survey revealed that the general opinion regarding the activity was highly positive. The undergraduates reviewed some stoichiometry concepts which we had previously observed that they had problems understanding. In addition, the attractive theme of haute cuisine made the activity dynamic and enjoyable both for students and for the teacher.

Emphasizing stoichiometry appears to be a norm of introductory chemistry courses. In this longitudinal and mixed-methods study, we examined how the emphasis on stoichiometry in assessments of introductory chemistry impacted educational equity and student learning. Using quantitative methods, we identified mole and stoichiometric conversions as two of the most frequently assessed and inequitable competencies, perpetuating systemic inequities in access to pre-college mathematics preparation. Above all other competencies, midterm assessments of stoichiometry were the most impactful as the strongest predictor of students' scores on both the first and second-semester introductory chemistry final exam. These results informed the development of a think-aloud protocol used to describe how students approached assessments of stoichiometry. Students described stoichiometry as a step-by-step series of calculations, rarely associating this algorithm with the process of a chemical reaction by which reactants break bonds and rearrange to form products. Student responses suggest stoichiometry substitutes learning how to apply chemistry to think about the problems scientists solve for memorizing algorithms to solve math problems in the context of chemistry. Shifting the foundation of introductory chemistry courses from algorithmic to applied competencies reflects scientific practice and maybe one strategy for educators to disrupt systemic barriers to access and retention in STEM Education. Based on these findings and the advancements of other research, we offer implications for supporting educators as they iteratively develop increasingly relevant and equitable assessments of introductory chemistry.

The purpose of this study was to examine how learners' problem-solving approaches and success changed from high school to graduate school. This case study included 15 participants who were purposefully selected regarding their grade levels. To examine the development, we asked three algorithmic questions and three problems, which were different from each other regarding the data given and the context provided by stoichiometry. The data were collected through a think aloud protocols. The participants were also requested to take notes, write equations, and make calculations. Deductive data analysis was conducted. Results showed that the participants were able to solve the algorithmic questions to some extent. However, all participants had some difficulty in solving the problems. Most of the participants did not use supportive approaches to solve the problems. Implications for chemistry teaching provided in light of the results.

To gauge the variability in expert problem-solving strategies for stoichiometry problems, a set of experts in different career tracks were studied with the cohort including 17 graduate students in chemistry, three college chemistry instructors, and seven college graduates working in the industry. The goal of the study was to determine whether variability would be observed based upon experience and career trajectories. The data were collected using interviews and analyzed qualitatively and quantitatively using the COSINE (Coding System for Investigating Sub-problems and Network) method. Although the method was developed for the analysis of undergraduate problem-solving, it appeared to be effective in examining experts' problem-solving in chemistry as well. The study revealed similar abilities for succeeding at solving a series of problems, but the strategies were variable for the three cohorts of experts. Specifically, the amount of information used to solve the problems differed across the three cohorts with graduate students focusing more upon each of the specific subproblems within each problem compared to industry chemists utilizing the big-picture approach in lieu of breaking down each problem into respective subproblems. Familiarity with the question types and ability to chunk information were common characteristics observed consistently for the expert participants, which is consistent with existing research.

This is an easy and inexpensive laboratory experiment in which undergraduate students at the Bachelor's degree level in Chemistry can measure formation constants of complexes [Ni(en)[subscript n](OH[subscript 2])[subscript 6-2n]][superscript 2]+ (n = 1, 2 or 3; en = ethylenediamine) through an acid-base titration. The background information necessary to understand the activity involves familiarity with equilibria and basic coordination chemistry, and the lab experience uses only common glassware and a pH meter. The mathematical treatment of the results is based on Bjerrum's formation function. Details of the activity, including full procedural and experimental data, are provided. The experiment can be augmented with additional work based on Job's method to analyze the stoichiometry of the complexes under investigation.

This research focuses on students' tactic assessments of 3 correlations with illustrated 2-step strategic map and animated presentations in stoichiometry. The participants were divided into 2 learning groups: the experimental and the control group by quasi-experimental approach. Most of all, experimental group participants have been contingent on critical performances of thinking capabilities in accordance with tactic fulfillments of 3 correlations helpfully. In contrast with statistic findings of post-tests, experimental group participants get more formulated goals of individual learning in answering 5 algorithmic and conceptual pairs of achievement test items than those of control group participants. Students' shift of reasoning from model-based to case-based requires them to explore an effective mental cognition and responses for full-fledged performances of problem-solving skills. After tactic fulfillments for 3 study objectives of visualized developments, experimental group participants have upgraded a distinct learning accumulation and project-based feedback at their best learning performances.

The study sought to find out difficulties encountered by high school chemistry students when solving stoichiometric problems and how these could be overcome by using a problem-solving approach. The study adopted a quasi-experimental design. 485 participants drawn from 8 highs schools in a local education district in Zimbabwe participated in the study. A validated stoichiometry achievement test was used to collect data at pre-test and post-test stages. The researchers also prepared a difficulty identification index to analyse the difficulties encountered by students. Quantitative data was analysed using inferential statistics and ANCOVA. From the findings, the difficulties identified were lack of understanding of the mole concept, inability to balance chemical equations, use of inconsistent stoichiometric relationships, identifying the limiting reagent, determination of theoretical yields and identification of substances in excess. The study also found that the use of problem-solving instruction as effective in remedying the identified difficulties in comparison to the conventional lecture method. It was strongly recommended that chemistry educators should analyse and understand student difficulties if they are to assist the learners to become confident and efficient problem solvers. Furthermore chemistry educators should implement the problem-solving pedagogical technique as a means of addressing the difficulties students have in stoichiometry problem-solving.

Stoichiometry calculation competence tends to be particularly poor in the developing world, even among teachers. Various methods, including the unit factor method, have the potential to be effective in developing such competence. To evaluate the likelihood of such a generic proportion method, which downplays traditional formula usage, succeeding in a particular context, it is necessary first to understand teachers' existing competence with proportion and the extent to which their calculation success relies on the explicit provision of and substitution into formulae in their written solutions. This quantitative survey study of 171 South African Physical Sciences teachers' use of formulae and proportion found that most teachers failed to recognise the need to use proportion for some of the four reaction-based stoichiometry calculation questions used. Provision of and substitution into a formula in the written solution was found to be valuable in helping participants who underutilised proportion to obtain process marks, but to be largely irrelevant to obtaining the correct answer. The findings suggest that professional development interventions in similar contexts should focus on proportion within stoichiometry, particularly on recognition of its relevance to reaction-based questions. While a generic proportion method is well suited to this purpose, questions are raised concerning the likelihood that teachers would accept such a method in a context where process marks favour traditional formats of formula provision and substitution and where process mark attainment is highly valued. The findings also point to the need for teacher education to address competencies other than proportion.

This study explored the effect of blended learning in terms of model-based collaborative learning in a small private online course (SPOC) environment on 10th graders' achievements in stoichiometry through a quasi-experimental design. The participants included 140 tenth graders assigned to two groups: (a) the experimental group, which studied in a blended environment (N = 69) and (b) the control group, which studied in a conventional lecture-based environment (N = 71). The results revealed that the experimental group exhibited significantly superior performance than the control group after the intervention and that the key factor in enhancing students learning is the teacher's facilitation. These findings implied that the blended model-based collaborative learning in a SPOC environment with proper design, facilitation, and face-to-face interaction groups provided students with opportunities to engage in learning to improve their achievements.

The present study investigated pre-service chemistry teachers' problem solving strategies and alternative conceptions in solving stoichiometric problems and later on formulate a teaching framework based from the result of the study. The pre-service chemistry teachers were given four stoichiometric problems with increasing complexity and they need to write the process that they undertake to solve the problem. The study found out that the most prominent strategy among pre-service chemistry teachers is the mole method, which is algorithmic by nature. Very few of them used the proportionality method and none made use of the logical method. Alternative conception noted among the pre-service chemistry teachers is that some of them rely on Avogadro's number in converting between moles with a given mass. The results indicate that these pre-service chemistry teachers has the tendency to teach stoichiometry using the mole method only and that they might carry on the alternative conception about Avogadro's number as they start their teaching career. It is therefore suggested that the teaching of stoichiometry to pre-service chemistry teachers should not be confined to demonstration as they will imitate such technique when they are already a full pledged chemistry teacher. They should be involved in the process of thinking of ways to solve the stoichiometric problem in such a way that it will help them become independent thinkers and be responsible for their own learning by developing metacognitive and critical thinking strategies.

Curriculum materials can play a major role in shaping teachers' thinking about instruction and content as well as serve as a support for teachers' learning. With the inclusion of engineering in NGSS, many teachers may be turning to existing curriculum materials to help them infuse engineering into their science classroom, especially when they do not have the time or opportunity for professional development sessions. In this study, we identified a sample of curriculum materials freely available online to chemistry teachers trying to incorporate engineering in the topics of stoichiometry and/or energy, common topics in secondary chemistry curricula. Using qualitative coding methods, we examined what this sample had to offer the chemistry teachers in the way of developing their understanding of engineering and teaching it. Our findings indicate that within our sample there are limited existing curriculum materials to support teachers' engineering incorporation into secondary chemistry, and the support for teachers varied in terms of content and usefulness across the materials. The materials provided procedural information for activities but lacked in supports for teacher learning and student development beyond the procedure. Implications for the enactment of NGSS in secondary science along with needs for curriculum development and teacher learning are discussed.

This activity allows students to visualize how to obtain different stoichiometries with various techniques in a single experiment. The involvement of three phases adds to the student's interest. Instructional materials are provided to facilitate the experimental procedures, interpretation of results, and error analysis. The reaction of Li from a Li battery with water inside a syringe allows measurement of the gas evolved, the metal consumed, and the hydroxide produced. Li batteries can be obtained for less than US $1.00. This report describes the development of a 2 h activity that has been tested in whole or in part in various teacher workshops in Mexico, Panama, El Salvador, and Thailand, and it has been implemented and assessed in a general chemistry laboratory.

What evidence counts as teacher quality is a debate of continued interest to the teacher education community. Many education scholars have argued for the importance of retention of knowledge as an indicator of the quality of education acquired. This study explored the retention of the quality of planned Topic Specific Pedagogical Content Knowledge (TSPCK) in a case study of seven chemistry pre-service teachers in their final year of study towards a BEd degree. They were exposed to a TSPCK based intervention in either Organic Chemistry or Stoichiometry as a topic and subsequently followed two years later into their practice as beginning teachers. The study employed a longitudinal qualitative research design with sets of data collected at three different points: pre-intervention, post-intervention and delayed post-intervention (two years later). Data collected included a combination of completed TSPCK tools and audio-recorded stimulated recall interviews. The analysis of completed TSPCK tools entailed the use of a criterion-based rubric for shifts in the quality of planned TSPCK and the recorded interviews were analysed through content analysis. Evidence of learning during the intervention and in-practice was analysed using the qualitative in-depth analysis for developing TSPCK and the Vygotskian sociocultural theoretical framework. Findings from the first and second sets of data confirmed a gain in the quality of planned TSPCK at the end of the intervention. The findings from the second and third sets revealed the beginning teachers' successful retention and continued growth two years in practice. Implications for teacher preparation are discussed.

Teachers' conceptual subject matter knowledge of stoichiometry is a global concern. Such knowledge is contextually dependent, as is the feasibility of attaining particular outcomes during in-service teacher education workshops. In an attempt to understand what is feasible in various contexts, I explore the relationships between South African physical sciences teachers' environments, education, and teaching experience and their possession of, and ease with which they learn, various types of stoichiometry knowledge. This is done through the analysis of the pre- and posttest and biographical survey data obtained from 184 teachers who attended a two-day stoichiometry workshop. The findings suggest that teachers teaching in contexts of poverty, particularly when lacking a B.Sc. degree, show a particularly high preference for algorithmic over conceptual knowledge. The success with which the teachers in the sample learned facts about relationships between concepts during the two-day workshop suggests that such an approach could provide an entry point into currently less feasible conceptual learning. No correlation was found between extent of tertiary chemistry study and stoichiometry subject matter knowledge, even for teachers with a B.Sc. degree. Statistically significantly higher levels of stoichiometry knowledge were found for the following teacher groupings compared to their counterparts: teaching in a school serving a socioeconomically more advantaged community; having over three years' teaching experience; possessing a B.Sc. degree. The suggestions derived for in-service teacher education targets are likely to have relevance in developing countries and in developed countries where considerable socioeconomic differences exist.

High school students find reaction stoichiometry and the concept of the mole hard to comprehend. Teachers are well aware of the importance of teaching the mole concept and also the difficulty associated with it. In an attempt to improve the understanding of the mole concept with reduced difficulty, an atomic model kit that provides a hands-on learning experience has been developed and implemented in a class of 40 students. Each model atom consists of spherical neodymium magnets (acting as nucleons) of appropriate number (1 for hydrogen, 12 for carbon, 14 for nitrogen, and 16 for oxygen) enclosed in a hollow spherical Styrofoam casing (acting as an atom) that can be opened when required. These model atoms can be easily weighed using a laboratory balance, to obtain mass ratios of 1:12:14:16. This model kit provides an opportunity to have a hands-on learning experience of abstract concepts such as mass conservation in a balanced chemical reaction, excess and limiting reagents, and the mole and its relation to gram atomic/molecular mass. Herein, we provide a detailed description of the design criteria and the construction of the model atoms. We also provide the activity sheets with the necessary instructions to carry out the hands-on activities and the assessment sheets used for evaluation.

There have been many practical obstacles for teachers to implement evidence-based educational technology, especially in STEM classrooms. By implementing learning principles related to Cognitive Load Theory, we developed an innovative Technology-Assisted Guided Learning (TAGL) approach and its web-based instructional tool, combining expertise from educational research and best teaching practices to enhance guided student-centered learning in chemistry. A total of 185 community college students were randomly assigned to learn stoichiometry through either TAGL or one of two active control interventions, traditional direct instruction and Khan Academy, a widely used web learning platform. We found that the TAGL group significantly outperformed both active control groups immediately after instruction, and furthermore, despite the fact that all groups received additional instruction in stoichiometry, the beneficial effects of TAGL compared to the control groups were maintained a month later. Notably, TAGL was able to eliminate the achievement gap between students with low prior knowledge and students with high prior knowledge. Furthermore, prior-knowledge activation was found to be especially beneficial for students with low prior knowledge. Our work contributes to existing research in learning theories and provides new insight toward the development of more effective and adaptive instructional designs. By translating research into practice, this study demonstrates the great potential of using innovative computer-based technology to improve student learning for all.

Theoretical yield and extent of reaction (degree of completion) are important concepts in stoichiometry and in chemical kinetics. We provide expressions describing theoretical yield (Y) and maximum extent of reaction (fractional yield, f[subscript max]) for five examples of commonly encountered reversible chemical reactions: A [equilibrium sign] B; A + B [equilibrium sign] C + D; A + B + C [equilibrium sign] D + E + F; A [equilibrium sign] B + C; and A + B [equilibrium sign] C. We discuss how the equilibrium constant and initial reactant concentration influence the maximum fractional yield (degree of reaction completion) and Y and illustrate their effects on specific examples of reversible reactions: conformer equilibria, esterification reaction, and ionization of weak acids.

Over the past decade the Accreditation Board for Engineering and Technology, Inc. (ABET) has changed the general chemistry requirements to include a single introductory course for most engineering majors. There is a focus on outcomes that equip students with the ability to pass the Fundamentals of Engineering (FE) Exam and to work in multidisciplinary teams. In designing the experiments for the general chemistry laboratory (CHM2045L) at Florida Polytechnic University, our focus has been on nontraditional laboratories that emphasize fundamental science concepts that challenge the student in a "maker chemistry" project that (1) highlights traditional lecture concepts, (2) engages the student in an active design and build project, and (3) directly demonstrates the application of chemical sciences to their field of study and society's technological needs. The present work describes a novel chemistry laboratory in which students etch a printed circuit board (PCB) and solder light-emitting diodes (LEDs) onto the PCB to construct a working device in a 2 h laboratory session focused on oxidation-reduction (redox) reactions and LED band gap emission.

The basolateral amygdala (BLA) is a temporal lobe structure that contributes to a host of behaviors. In particular, it is a central player in learning about aversive events and thus assigning emotional valence to sensory events. It is a cortical-like structure and contains glutamatergic pyramidal neurons and GABAergic interneurons. It is divided into the lateral (LA) and basal (BA) nuclei that have distinct cell types and connections. Interneurons in the BLA are a heterogenous population, some of which have been implicated in specific functional roles. Here we use optogenetics and slice electrophysiology to investigate the innervation, postsynaptic receptor stoichiometry, and plasticity of excitatory inputs onto interneurons within the BLA. Interneurons were divided into six groups based on their discharge properties, each of which received input from the auditory thalamus (AT) and auditory cortex (AC). Auditory innervation was concentrated in the LA, and optogenetic stimulation evoked robust synaptic responses in nearly all interneurons, drove many cells to threshold, and evoked disynaptic inhibition in most interneurons. Auditory input to the BA was sparse, innervated fewer interneurons, and evoked smaller synaptic responses. Biophysically, the subunit composition and distribution of AMPAR and NMDAR also differed between the two nuclei, with fewer BA IN expressing calcium permeable AMPAR, and a higher proportion expressing GluN2B-containing NMDAR. Finally, unlike LA interneurons, LTP could not be induced in the BA. These findings show that interneurons in the LA and BA are physiologically distinct populations and suggest they may have differing roles during associative learning.

Students who score within the bottom quartile on cognitive measures of math aptitude have been identified as at-risk for low performance in chemistry courses, with less attention as to "why" such differential performance persists. At-risk students struggle most differentially on assessment items related to the mole concept and stoichiometry. An exploration as to the nature of the differential performance observed became of great interest as the assessment of these topics rarely progresses beyond multiplication or division, and at-risk students who achieved proficiency with the mole concept and stoichiometry had no noticeable gaps in academic chemistry performance when compared to students scoring in the top three quartiles of math aptitude. Thus, students in first-semester general chemistry were surveyed to describe their solution processes toward assessment items involving the mole concept and stoichiometry. Three hundred and forty-eight students responded to all survey prompts with 101 identified as at-risk. Findings suggest that while all students were observed to struggle in the conceptualization of the algorithms by which they execute solution processes, not-at-risk chemistry students were more likely to achieve correct answers via chemically implausible solution pathways. Rather than suggest the removal of assessment practices involving algorithmic, multiple-choice assessment on these topics, the implications include practical suggestions and opportunities for further research toward improving the equitability of measures used to assess proficiency with stoichiometry.

Stoichiometry, which deals with the quantitative aspects of Chemistry, is a topic students find challenging and which teachers struggle to teach. South African students' performance in stoichiometry in the final matriculation examinations has led to calls for the topic to be taught better and highlighted the need for teacher professional development. This served as the rationale for this study to design an instrument to measure the quality of experienced Physical Science teachers' topic-specific pedagogical content knowledge (TSPCK) using a mixed-methods approach. Responses by five teachers to open questions on each of five components of TSPCK were used to generate scenario-based items for the instrument. The validity of the instrument was determined through Rasch analysis of responses of a sample of 31 teachers. Both the validity and reliability of the instrument to measure the quality of TSPCK in stoichiometry were found to be acceptable based on the fit statistics and reliability measures generated from the Rasch analysis.

The problem-solving strategies of students enrolled in general chemistry courses have been the subject of numerous research investigations. In most cases, the investigators were interested in the specific areas or concepts that posed the greatest difficulty to a student's success in achieving the correct answer. However, the investigation reported here is based on a study of student problem-solving habits that have been classified by the authors as minor variables: what is the first step that the students complete, how fluent is their work, do they check their work at the end of the process? While these minor variables do not directly evaluate a student's knowledge of chemistry, the results indicate a clear correlation between those students who are "successful" and those students who are "unsuccessful" on a written exam. The data were obtained via observation during think-aloud sessions held in a Midwestern university in the United States of America. The aim of this study is to give educators an understanding of the strategies used by the students as well as provide instructors with visual cues regarding a student's success in problem solving. These problem-solving habits may not directly affect the student's ultimate solution of a single problem, but can indirectly influence their overall performance in either a positive or negative manner.

The presented strategy of chemistry calculation is based on mole-concept, but it uses only one fundamental relationship of the amounts of substance as a basic panel. The name of LEGO-method comes from the famous toy of LEGO[R] because solving equations by grouping formulas is similar to that. The relations of mole and the molar amounts, as small perspicuous units (building blocks), are applied on the fundamental relationship (basic panel) and the problem can be solved as an algebraic operation. LEGO-method is much more simple than the other strategies (e.g., dimensional analysis, mole method or rule of three), because the students can understand and learn this procedure step by step at the very beginning of their science study. The measurements have demonstrated that those students, who learned the LEGO-method in the school, have used this strategy more frequently than other strategies for solving a stoichiometric problem. The success of these students indicates that the LEGO-method is a useful alternative strategy for teaching chemistry calculations and more complete understanding of problem-solving. (Contains 1 figure.)

The "Atoms-First" approach has received considerable attention in the chemical education community over the past few years as an alternative to the standard reaction-based two-semester General Chemistry curriculum. The Atoms-First model emphasizes the electronic structure of the atom as a means to explain and rationalize chemical reactions and stoichiometry, which are then covered at the end of the first semester. The current study analyzes the results of switching from a traditional reaction-based curriculum to an Atoms-First approach in a two-semester General Chemistry course with regards to student performance on standardized American Chemical Society (ACS) exams. The study evaluated roughly 600 students over three years of classes, and found that the outcomes were generally favorable for topics related to atomic and molecular structure. A comparison of the two approaches and suggestions for implementation of the Atoms-First approach are also included.

This paper proposes a novel application of knowledge space theory for identifying discrepancies between the knowledge structure that experts expect students to have and the real knowledge structure that students demonstrate on tests. The proposed approach combines two methods of constructing knowledge spaces. The expected knowledge space is constructed by analysing the problem-solving process, while the real knowledge space is identified by applying a data-analytic method. These two knowledge spaces are compared for graph difference and the discrepancies between the two are analysed. In this paper, the proposed approach is applied to the domain of stoichiometry. Although there was a decent agreement between expected and real knowledge spaces, a number of relations that were not present in the expected one appeared in the real knowledge space. The obtained results led to a general conclusion for teaching stoichiometry and pointed to some potential improvements in the existing methods for evaluating cognitive complexity.

The identification of students at risk for academic failure in undergraduate chemistry courses has been heavily addressed in the literature. Arguably one of the strongest and most well-supported predictors of undergraduate success in chemistry is the mathematics portion of the SAT (SAT-M), a college-entrance, standardized test administered by the College Board. While students scoring in the bottom quartile of the SAT-M (herein referred to as at-risk) perform significantly worse on first-semester chemistry assessments, little is known of the topics on which these students differentially struggle. The purpose of this study is to provide insight as to which first-semester chemistry topics present an incommensurate challenge to at-risk students. Students were identified as either at-risk or not at-risk via SAT-M scores. Students' assessment responses were collected across four semesters of first-semester chemistry courses at a large, public university (N = 5636). At-risk students struggled consistently across all topics but disproportionately with mole concept and stoichiometry. Analyzing the trend in topics suggests that the struggles of at-risk students are not entirely attributable to topics that rely heavily on algorithms or algebraic math. Moreso, at-risk students found to have performed well on mole concept and stoichiometry went on to perform similarly as their not at-risk peers. The results support an instructional emphasis on these topics with reviewed literature offering promising, practical options to better serve at-risk students and broaden representation in the sciences.

This case study demonstrates the ability of high school chemistry students, with varying levels of math preparation, to experience learning-gains on state and district assessments as it relates to chemical reactions, thermodynamics, and kinetics. These advances were predicated on the use of a teaching style rooted in abstract reasoning. The methodology was presented to students and modeled by the instructor over an entire school year to reinforce key proportional relationships featured in the balanced chemical equation and related topics such as acids and bases, reaction rates, equilibrium, and conservation of matter. Despite the small sample size, there was a general increase in student success, indicated by a statistically significant difference between students receiving instruction rooted in concrete reasoning and students receiving instruction rich in abstract reasoning.

Analyzing and interpreting data is an important science practice that contributes toward the construction of models from data; yet, there is evidence that students may struggle with making meaning of data. The study reported here focused on characterizing students' approaches to analyzing rate and concentration data in the context of method of initial rates tasks, a type of task used to construct a rate law, which is a mathematical model that relates the reactant concentration to the rate. Here, we present a large-scale analysis (n = 768) of second-semester introductory chemistry students' responses to three open-ended questions about how to construct rate laws from initial concentration and rate data. Students' responses were coded based on the level of sophistication in their responses, and latent class analysis was then used to identify groups (i.e. classes) of students with similar response patterns across tasks. Here, we present evidence for a five-class model that included qualitatively distinct and increasingly sophisticated approaches to reasoning about the data. We compared the results from our latent class model to the correctness of students' answers (i.e. reaction orders) and to a less familiar task, in which students were unable to use the control of variables strategy. The results showed that many students struggled to engage meaningfully with the data when constructing their rate laws. The students' strategies may provide insight into how to scaffold students' abilities to analyze data.

The first-semester introductory organic chemistry laboratory has been adapted to include mini postlab assignments that students must complete correctly, through as many attempts as prove to be necessary. The use of multiple drafts of writing assignments is a standard approach to improving writing, so the system was designed to require drafts for assignments that involve calculations, NMR interpretation, the creation of good figures, and other nonwriting forms of analysis. The system was created to require students to pay attention to faculty feedback and to review their own work. Scores on a written lab final suggest that the "Do It Right!" system has had a statistically significant improvement in students' abilities to perform stoichiometric calculations and to answer questions about a standard aqueous workup.

Making optimal pedagogical and predictive use of the radius ratio rule to distinguish between solid state structures that feature tetrahedral, octahedral and cubic holes requires several updated insights. A comparative analysis of the Born-Landé equation for lattice energy is developed to show that the rock salt structure is a suitable choice for radius ratios between 0.326 and 1.00. The lower bound is the ratio at which the energy of the rock salt structure matches that of the zinc blende structure, all other things being equal. The upper bound extends all the way to unity because the relative energy of the rock salt and CsCl structures are within 1% of each other for radius ratios above 0.717, which is the ratio at which the energy of the rock salt structure matches that of the CsCl structure. Geometric analysis of 154 1:1 ionic compounds that can potentially adopt the zinc blende, rock salt, or CsCl structure demonstrates that while existing ionic radii can be used for predictions with substantial success, a more applicable set of predictive ionic radii based on cubic lattice parameters can be deduced.

A good understanding of ternary phase diagrams is required to advance and/or to reproduce experimental research in solid-state and materials chemistry. The aim of this paper is to describe the solutions to problems that appear when studying or determining ternary phase diagrams. A brief description of the principal features shown in phase diagrams of ternary systems in the subsolidus region is included. We present a systematic procedure to obtain specific compositions of particular interest as well as to calculate binary and ternary ratios of compounds inside the Gibbs triangle and a step-by-step methodology to formulate solid solution equations in binary, ternary, or higher-composition compounds. Specific problems and their solutions are presented as a practical guide, linking the learned concepts with their applications in ceramics and solid-state chemistry research. In addition, ready-to-go exercises with worked-out solutions are included for practice. The procedures described herein may be helpful to those interested in phase diagram interpretation, preparation, and analysis.

Organic chemistry students struggle with multiple aspects of reaction mechanisms and the curved arrow notation used by organic chemists. Many faculty believe that an understanding of nucleophiles and electrophiles, among other concepts, is required before students can develop fluency with the electronpushing formalism (EPF). An expert concept map was created to depict an understanding of nucleophiles and electrophiles ideally held by undergraduates. Second year organic chemistry students were interviewed and asked to give examples of nucleophiles and electrophiles and to identify them in reactions. A cognitive map was created to represent each student's understanding. The students' maps were compared to the expert map, revealing that students possess fragmented ideas about the structure and function of nucleophiles and electrophiles.

The purpose of this study was to investigate the analytical thinking abilities and attitudes towards science learning of grade-11 students through science, technology, engineering, and mathematics (STEM) education integrated with a problem-based learning in the study of stoichiometry. The research tools consisted of a pre- and post-analytical thinking ability test, a science learning attitude test, classroom observations, student reflective journals, and semi-structured interviews. The findings indicated that STEM learning activities based on problem-based learning successfully developed analytical thinking abilities and attitudes towards science learning. Consequently, the students realized how important theories are, and were able to integrate their knowledge from various fields to solve problems and to create new innovations. About 80% of the students showed higher analytical thinking ability scores above the prescribed criterion of 70% of the full score. After learning, the scores of the students were higher than those before learning at a confidence level of 0.01. The attitudes towards science learning were higher than those before learning at a confidence level of 0.01. The successful activities of STEM started with offering knowledge to students through an inquiry-based process until they could construct the knowledge on their own. After that, the teacher initiated a problem situation and allowed each group of students to create a useful product adopted from the experimental results via integrating STEM knowledge to modify their creative works.

The binding constant and stoichiometry ratio for the formation of iron(II)-(1,10-phenanthroline) or iron(II)-o-phenanthroline complexes has been determined by a combination of a low-cost analytical method using a smartphone and a molecular modeling method as a laboratory experiment designed for analytical and physical chemistry courses. Intensity values were obtained from the digital images by measuring the RGB (red, green, blue) values (on a scale of 0-255 in intensity) of the samples between Fe(II) and o-phenanthroline using a digital camera from a smartphone. The R channel showed the best linearity for predicting the binding constant. For computational studies, iron(II) complexes using water molecules and 1,10-phenanthroline were used to evaluate the stability of the complex by varying the number of ligands. Complexes have been optimized by reaching a minimum amount of energy. It was possible to observe how stable the complexes are from the optimization calculations, including aspects about the achieved geometries. The approach provides a simple method for performing stability constants over a wide range of complexes, from the undergraduate chemistry laboratories, in the field, and in the research laboratory.

Students' inaccurate ideas about what is represented by chemical equations and concepts underlying stoichiometry are well documented; however, there are few classroom-ready instructional solutions to help students build scientifically accurate ideas about these topics central to learning chemistry. An intervention (two inquiry-based activities) was developed, piloted, and evaluated with common misconceptions in mind. The intervention was carried out in five sections of a high school chemistry class at a technical career campus, and pre/posttest data using a published instrument were collected to evaluate the intervention's effectiveness in building accurate stoichiometric concepts. Statistically significant growth with a large effect size occurred from pre to posttest demonstrating that the intervention improved conceptual understanding even though there were variations in the intervention delivery, as well as small differences detected between 11th and 12th grade student performance. The study, an action research project carried out by a teacher enrolled in a long-term professional development program, has implications for the value of rigorous materials design and evaluation framed by the chemistry education research literature. Study replication in other classroom contexts would be useful in further validating the learning outcomes of the activities. For practitioners, the activities studied here are free and available online for classroom use.

A series of pedagogical problem set exercises are posed that illustrate the principles behind material efficiency green metrics and their application in developing a deeper understanding of reaction and synthesis plan analysis and strategies to optimize them. Rigorous, yet simple, mathematical proofs are given for some of the fundamental concepts, particularly how metrics for overall plan material performance are related to their composite counterparts for individual reactions. Throughout this exposition, whenever a synthesis scheme is examined, it is converted into a compact tree diagram that is used to depict plans of any degree of complexity (linear or convergent) as a means to conveniently keep track of all reagents, intermediates, reaction yields, stoichiometric coefficients, number of branches, number of reaction steps, and convergent steps. We demonstrate that such tree diagrams facilitate the computation of material efficiency metrics for any individual reaction in a plan as well as for the entire plan. We also show how such diagrams may be used to plan schedules for reaction operations when multiple linear branches are run concurrently. For brevity the Supporting Information contains full solutions to posed problems.