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This study seeks to examine the effectiveness of peer-led team learning (PLTL) pedagogy when it is implemented in an entirely online environment. Past evaluations of PLTL have demonstrated the effectiveness of this approach when used with in-person teaching, but an online environment is expected to pose unique challenges to students, and therefore, the past work may not generalize to an online environment. The study implemented PLTL within four classes of second-semester general chemistry each offered online. The classes were evaluated in reference to six classes of the same course, also taught exclusively online, that relied primarily on didactic instruction. The evaluation showed the average score for students with online PLTL ranged from 0.15 to 0.20 standard deviations better than students with online didactic across the tests and final exams and that this difference was partially explained by past performance. Further, online PLTL students had a higher likelihood of earning a passing grade in the class which corresponded with a lower proportion of students failing and a lower proportion of students withdrawing from the course. The results indicate that PLTL was an effective instructional technique within an online modality at the research setting.

Prior research has demonstrated the important role of chemistry students' affect in academic performance. Likert-scale surveys are the most prevalent tools to measure students' affect within chemistry education research, however, data collected through a Likert-scale survey may exhibit response style bias which can hinder accurately measuring students' affect. This study investigates the utility of a novel survey methodology, termed rank-sort survey, in understanding students' academic motivation in a general chemistry course. Informed by Q methodology, in a rank-sort survey participants rank a set of statements in terms of level of agreement with limits in place on how many items can be assigned a particular rank. In this investigation, a rank-sort survey was developed by using statements from an existing Likert-scale instrument, the Academic Motivation Survey in Chemistry. Data collected from the rank-sort surveys, compared to Likert-scale surveys, showed a better alignment with self-determination theory, the underlying theoretical framework, and a better ability to predict students' academic performance in chemistry. The study also discusses which surveys in chemistry education research are likely to benefit from adopting a rank-sort approach.

Representations are ubiquitous in chemistry. They are part of the chemistry language instructors use to communicate chemistry phenomenon to students. Literature calls in support of learning with multiple representations, but there is a pre-requisite for students to learn from a single representation. In this exploratory study, 1086 students in second semester general chemistry were randomly assigned to one of four representations showing bonding of sulfur dioxide: chemical formula, Lewis dot structure, an image of a ball and stick model, or an image of a space filling model. Students were asked to predict chemical properties of sulfur dioxide: relative bond length, molecular polarity, and the strongest intermolecular force with a water molecule. Using the lens of Multimedia Learning Theory on Learning with Text and Visual Representations, analyses of students' prediction of chemical properties and the features cited when making predictions was conducted. Effect sizes were used to describe variations among representations in terms of how students predicted bond length, polarity and intermolecular forces. Meaningful differences were found across representations in students' ability to correctly predict relative bond length and molecular polarity. These explorations generated the following hypotheses: (1) chemical formula leads students to depend on chemical conventions, (2) Lewis dot structure hinders predicting polarity when it shows an inaccurate shape, and (3) visual representations of ball and stick and space filling cue students to rely on visual estimations more than the other representations. Upon further testing, these hypotheses can inform instructors how to introduce representations and in the decision-making process of which representations to use to convey or assess a specific chemical property.

Some students struggle with chemistry because they do not find the relevance between chemistry content and their lives or they perceive their intelligence as fixed. Social-psychological interventions (SPIs), brief interventions that target students' subjective experiences, were developed to address these issues. As a result, SPIs have been associated with gains in students' academic performance, attitude, and persistence in various instructional settings; however, only a limited number of studies have explored SPIs within a chemistry context. This study evaluated the effectiveness of two SPIs, a growth mindset intervention (GMI) and a utility value intervention (UVI), on promoting students' academic performance and attitude in a general chemistry course with a large class size. This study also explored a theoretical explanation for the relationship among SPIs, attitude, and academic performance. Each SPI was designed to facilitate instructional adoption and was implemented by posting three prompts incorporated into homework assignments. The results show that the UVI led to a consistent improvement in student achievement, and among students who begin the course with lower attitudes toward chemistry, the UVI led to an improvement in students' emotional satisfaction and utility value. The UVI's improvement in academic performance was also observed with a group of students who have been underrepresented in the sciences, although a smaller sample size prevented finding statistical significance. The GMI improved academic performance relative to a comparison group but not to the extent observed with the UVI. The cost-to-benefit ratio associated with adopting SPIs within chemistry instruction seems highly favorable and thus warrants strong consideration among chemistry instructors.

Conceptually understanding chemistry requires the ability to transition among representational levels to use an understanding of submicroscopic entities and properties to explain macroscopic phenomena. Past literature describes student struggles with these transitions but provides limited information about upper-level post-secondary chemistry students' abilities to transition among levels. This group is of particular interest as they are engaging in potentially their final training before entering a career as professional chemists, thus if students are likely to develop this skill during their formal education it should be manifest among this group. This study characterized analytical chemistry students' responses to open-ended assessments on acid--base titrations and thin-layer chromatography for the use of sub-microscopic entities or properties to explain these macroscopic phenomena. Further, to understand whether explanatory statements were an expectation inherent in the instructional context of the setting, the analytical chemistry instructor's lectures on acid--base titrations and thin-layer chromatography were analyzed with the same framework. The analysis found that students seldom invoked explanatory statements within their responses and that congruence between lectures and responses to assessment was primarily limited to the use of macroscopic, descriptive terms. Despite the fact that the lecture in class regularly invoked explanatory statements in one context, this did not translate to student use of explanatory statements. To further test the hypothesis that analytical chemistry students struggle with explanatory statements, a follow-on study was also conducted among a second cohort of students reviewing their responses when specifically prompted to use sub-microscopic entities to explain a macroscopic phenomenon. The results suggest that fewer than half of the students showed proficiency on generating explanatory statements when explicitly prompted to do so. Instructional implications to promote explanatory statements are proposed in the discussion.

This paper is designed to synopsize the efforts of a team of general chemistry teachers to enact assessments during the abrupt transition to online-only instruction and reflect on what was done successfully and what could be improved. The focus is on the extent remote, online assessments accurately measured student knowledge described within the context of the decisions made for administration of the assessments. To limit the extent of unintended student collaboration, exams were given at a set day and time; question banks were developed so that students received variants of similar questions, and a remote proctoring software was used. Correlations showed consistency between online exams and paper exams, alleviating concerns that widespread cheating may take place. A concern was found with reusing the same exam at a later date for students who missed the original exam despite efforts to keep the online exam secure. The generation of alternative exams for later dates is recommended, potentially supported by creating and curating an online repository of assessment items to utilize.

The submission of a traditional postgraduate research thesis (or dissertation) is a milestone achievement that should be celebrated and has been regarded as a rite of passage. This major document has normally occupied a significant amount of mental space and time, often involving a frantic and intense period of writing to meet the submission deadline. Immediately after submission, research supervisors inevitably turn their attention to thoughts of publications. Some students are fortunate and will have managed to generate several publications during their postgraduate research but for most this represents a daunting process. In recent years, speculation regarding a new paradigm for the PhD thesis and its examination has emerged. In many countries, including Europe and Australasia, there has been a shift towards integrating separate publications with conventional chapters to assemble a thesis or dissertation by publication, which is often referred to as a ''cumulative thesis or dissertation'' (Christianson et al., 2015; Mason and Merga, 2018; Frick, 2019). Regardless, the outcome is likely to be that students will be required to engage in the publication process at a much earlier point in their studies and thesis examination will require a different approach to evaluating the contribution of the candidate as an author. In chemistry education research, the traditional thesis structure is still a prevalent format so the process of converting a sometimes circuitous and very personal research journey into concise peer-reviewed articles requires careful consideration. In this article, the authors have brought together some thoughts from the editorial team to guide the process of publishing postgraduate research (PhD or Masters) in the "Chemistry Education Research and Practice" ("CERP"), being mindful that in the future, a different approach to mentoring novice authors in the process of publication may be necessary.

Calls for assessments incorporating representations beyond the symbolic level (e.g., chemical reactions and formulas) have encouraged assessment designers to choose from a variety of representations in the design of chemistry assessments. This work expands on prior work in considering how representations are incorporated within assessments. First, students were given assessment items similar in task with common rationales for the design of answer choices with different representations "substituted" across the items. Second, students were randomly assigned to items identical in prompt, answer choices, and symbolic representation with experimental items "supplementing" symbolic representation with particulate or mathematical representation. The impact was operationalized as student performance, the performance of at-risk chemistry students scoring in the bottom quartile of the cohort's standardized math test scores, and on the answer choices to which students attend. Substituting symbolic for particulate representation had a significant, negative impact on overall and at-risk student performance and a considerable impact on students' selection of distractors. However, supplementing symbolic with a particulate representation had no discernible impact. Supplementing symbolic representations with tables including a column for "moles" had a significant, positive impact on overall student performance with considerable improvement observed among at-risk students. Students' selection of a distractor representative of a failure to apply a mole-to-mole ratio was reduced when symbolic representations were supplemented with tables. Practical implications for the use of representations in a more equitable assessment design, and as a learning experience for students overall, are described.

The methodological limitations education researchers face in the evaluation of reformed instruction have led to debates as to the evidence advancing evidence-based practices. To conduct more effective research, methodological pluralism in the evaluation of educational reforms can be used to complement the strengths and limitations of a corpus of literature informing the impact of an evidence-based practice. This study seeks to introduce randomization tests, a nonparametric statistical analysis incorporating a random-assignment component that can be applied to a single-subject (N = 1) research design, as a methodology to be counted amongst evaluations of instructional reforms. To demonstrate the utility of this approach, an evaluation of peer-led team learning (PLTL) for classes of second-semester general chemistry spanning 7 semesters was conducted using randomization tests. The design contributes novel understandings of PLTL including differences in effectiveness across instructors, trends in effectiveness over time, and a perspective as to the appropriateness of assumptions concerning statistical independence when applied to educational settings. At the research setting, four instructors (each constituting an individual case) alternated implementing lecture-based instruction and PLTL by term. Across these four instructors, the treatment effects of peer-led team learning when compared to lecture-based instruction ranged in impact (from d = 0.233 to 2.09). For two instructors, PLTL provided a means by which to significantly reduce the differential performances observed of students with variable preparations in mathematics, thereby advancing the equitability of their courses. Implications of this work include the incorporation of single-subject research designs in establishing evidence-based instructional practices, the effectiveness of PLTL as interpreted in a methodologically pluralistic context of the research literature, and enacting measurements of equity when gauging the success of instructional reforms in science. Further, this introduction to randomization tests offers another methodology for the evaluation of instructional reforms more widely applicable in educational settings with smaller sample sizes ("e.g.," reforms conducted within a single classroom or upper-level courses with small class sizes).

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.

We report on a highly significant, positive association between anthrax vaccination and occurrence of Gulf War Illness (GWI) in 111 Gulf War veterans (42 with GWI and 69 controls). GWI was diagnosed in 47.1% of vaccinated veterans but only in 17.2% of non-vaccinated veterans (Pearson χ2 = 7.08, p = 0.008; odds ratio = 3.947; relative risk = 2.617), with 1.6x higher GWI symptom severity in vaccinated veterans (p = 0.007, F-test in analysis of covariance). Next, we tested the hypothesis that the susceptibility to GWI following anthrax vaccination could be due to inability to make antibodies against the anthrax protective antigen (PA), the key protein contained in the vaccine. Since the first step in initiating antibody production would be the binding of PA peptide fragments (typically 15-amino acid long [15-mer]) to peptide-binding motifs of human leukocyte antigen (HLA) Class II molecules, we assessed the binding-motif affinities of such HLA specific molecules to all linear 15-mer peptide fragments of the anthrax PA. We identified a total of 58 HLA Class II alleles carried by the veterans in our sample and found that, of those, 18 (31%) were present in the vaccinated group that did not develop GWI but were absent from the vaccinated group who developed GWI. Remarkably, in silico analyses revealed very high binding affinities of peptide-binding motifs of those 18 HLA alleles with fragments of anthrax vaccine PA, leading to the successful production of anti-PA antibodies. Conversely, the absence of these protective HLA alleles points to a reduced ability to develop antibodies against PA, thus resulting in harmful PA persistence and development of GWI. [ABSTRACT FROM AUTHOR]

Reproductive phasiRNAs (phased, small interfering RNAs) are broadly present in angiosperms and play crucial roles in sustaining male fertility. While the premeiotic 21-nt (nucleotides) phasiRNAs and meiotic 24-nt phasiRNA pathways have been extensively studied in maize (Zea mays) and rice (Oryza sativa), a third putative category of reproductive phasiRNAs-named premeiotic 24-nt phasiRNAs-have recently been reported in barley (Hordeum vulgare) and wheat (Triticum aestivum). To determine whether premeiotic 24-nt phasiRNAs are also present in maize and related species and begin to characterize their biogenesis and function, we performed a comparative transcriptome and degradome analysis of premeiotic and meiotic anthers from five maize inbred lines and three teosinte species/subspecies. Our data indicate that a substantial subset of the 24-nt phasiRNA loci in maize and teosinte are already highly expressed at the premeiotic phase. The premeiotic 24-nt phasiRNAs are similar to meiotic 24-nt phasiRNAs in genomic origin and dependence on DCL5 (Dicer-like 5) for biogenesis, however, premeiotic 24-nt phasiRNAs are unique in that they are likely i) not triggered by microRNAs, ii) not loaded by AGO18 proteins, and iii) not capable of mediating PHAS precursor cleavage. In addition, we also observed a group of premeiotic 24-nt phasiRNAs in rice using previously published data. Together, our results indicate that the premeiotic 24-nt phasiRNAs constitute a unique class of reproductive phasiRNAs and are present more broadly in the grass family (Poaceae) than previously known. [ABSTRACT FROM AUTHOR]

Introduction: The Strengths and Difficulties Questionnaire (SDQ) is one the most widely used behavior screening tools for public schools due to its strong psychometric properties, low cost, and brief (25-question) format. However, this screening tool has several limitations including being primarily developed for the purposes of identifying clinical diagnostic conditions and primarily in a European population. To date, there has been minimal comparative research on measurement invariance in relationship to important U.S. socio-demographic metrics such as race and gender. Method: This study utilized both structural equationmodeling (i.e., confirmatory factor analysis) and item response theory (IRT) methods to investigate the measurement invariance of the SDQ across gender (male, female) and race (Black, White). CFA analyses were first conducted for each of the SDQ subscales to identify potential misfit in loadings, thresholds, and residuals. IRT-graded response models were then conducted to identify and quantify the between-group differences at the item and factor levels in terms of Cohen's d styled metrics (d > 0.2 = small, d > 0.5 = medium, d > 8 = large). Results: There were 2,821 high school participants (52% Male, 48% Female; 88% Black, 12% White) included in these analyses. CFA analyses suggested that the item-factor relationship for most subscales were invariant, but the Conduct Problems and Hyperactivity subscales were non-invariant for strictmeasurement invariance. IRT analyses identified several invariant items ranging from small to large. Despite moderate to large effects for item scores on several scales, the test-level effects on scale scores were negligible. Discussion: These analyses suggest that the SDQ subscale scores display reasonable comparable item-factor relationships across groups. Several subscale item scores displayed substantive item-level misfit, but the test level effects were minimal. Implications for the field are discussed. [ABSTRACT FROM AUTHOR]

There has been an increased use of authentic practices in both science and environmental education in recent years. Such practices can utilize social constructivist frameworks to consider the learning that may be taking place as students become engaged in tool use. The current study focuses on a group of elementary school students studying the Everglades in the field and in a classroom setting during one academic year. In particular, we observed students' use of tools (identified as tool-conventions to include both artifacts and conventions) and compared their use in both settings. We found that in the field, students spent considerable amount of time engaged in data collection activity such as taking observations and measurements that resembled what scientists might be doing and included the invention of new tools to facilitate data gathering. In this context, students generally worked more independently from the teacher, collaborated in small work groups, and engaged in more self-directed inquiry. In the classroom, while some of the scientific field tools were practiced in anticipation of their use in the field, activity included more teacher direction, often resembling what might be found in other types of classroom work and the tools used there often supported this work. Models of tool use based on Yrjo Engestrom's activity approach were constructed for both settings. Implications of the results include the importance of viewing tool use in authentic learning with a sociocultural and activity perspective to reflect the socially constructed nature of such learning. (Contains 5 figures, 1 table, and 3 endnotes.)

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.

The Achievement Goal Framework describes students' goal orientations as: task-based, focusing on the successful completion of the task; self-based, evaluating performance relative to one's own past performance; or other-based, evaluating performance relative to the performance of others. Goal orientations have been used to explain student success in a range of educational settings, but have not been used in post-secondary chemistry. This study describes the goal orientations of General Chemistry students and explores the relationship of goal orientations to success in the course. On average, students report higher task and self orientations than other orientation. Task orientation had a positive relationship with exam performance and self orientation had a negative relationship with exam performance. Clustering students showed that for the majority of students task and self orientations moved concurrently and students with low preference across the three orientations also performed lowest on exams. Finally, students in classes using Flipped-Peer Led Team Learning, a pedagogy designed to bring active learning to a large lecture class, showed higher task orientation than those in classes with lecture-based instruction.

Meta-analysis can provide a robust description of the impact of educational reforms and also offer an opportunity to explore the conditions where such reforms are more or less effective. This article describes a meta-analysis on the impact of cooperative learning on students' chemistry understanding. Modifiers in the meta-analysis are purposefully chosen to model instructors' decisions in implementing cooperative learning. Modifiers investigated include: using cooperative learning periodically or in every class period; setting a maximum group size at four or smaller versus five or larger; using closed-ended or open-ended assessments; and assessing a single topic or assessing the cumulative topics in the course. The results showed cooperative learning's effectiveness is robust across a wide range of instructional decisions except no evidence of effectiveness was found with cumulative assessments. The overall results from the meta-analysis provide a benchmark for evaluating future efforts to evaluate pedagogical interventions in chemistry.

The research-based pedagogical strategy of flipped classes has been shown to be effective for increasing student achievement and retention in postsecondary chemistry classes. The purpose of flipped classes is to move content delivery (e.g., lecture) outside of the classroom, freeing more face-to-face time for active learning strategies. The opportunity to engage in active learning with students can be a challenge for instructors of large classes (more than 100 students). Furthermore, there has been little discussion in the chemical education literature to provide instructors with detailed descriptions of successful implementations of flipped classes combined with active learning in large classes. To this end, this report provides a comprehensive description and evaluation of a coordinated implementation of flipped classes with peer-led team learning (PLTL) for second-semester general chemistry with class sizes greater than 200 students. This approach is described as "Flipped PLTL." This report includes details about creation of videos for flipped instruction, class structure, and the recruiting and training of peer leaders. The purpose of this paper is to provide an example of flipped classes with PLTL that can guide other instructors who wish to implement these pedagogies in large classes.

A well-established literature base identifies a portion of students enrolled in post-secondary General Chemistry as at-risk of failing the course based on incoming metrics. Learning about the experiences and factors that lead to this higher failure rate is essential toward improving retention in this course. This study examines the relationship between study habits and academic performance for at-risk students in General Chemistry. Students who were in the bottom quartile of SAT math scores were identified as at-risk students. The study habits of General Chemistry students, both those identified as at-risk and those not identified were measured by text message inquiries. The text message asked ''Have you studied for General Chemistry I in the past 48 hours? If so, how did you study?'' twice a week throughout a semester. Student responses to the messages were used to calculate the frequency of studying throughout the term. The results from a multiple regression analysis showed that high frequency of studying could mitigate the difference between at-risk and non-at-risk students on final exam scores. Additionally, the quality of studying for six at-risk students was analyzed by student interviews in concert with their text message responses. The results indicated that the quality of studying is not necessarily linked to frequency of studying and both quality and frequency can play a role in at-risk students' academic performance. The results presented offer a path for at-risk students to succeed in General Chemistry and the methodology presented offers a potential avenue for evaluating future efforts to improve student success.

Mid-infrared optics require optical coatings composed of high- and low-refractive-index dielectric layers for the design of optical mirrors, filters, and anti-reflection coatings. However, there are not many technologies for depositing a material with a refractive index of less than 2 and a low loss in the mid-infrared region. Here, we present a unique deposition method of crosslinked polyethylene thin film for mid-IR optical filter design. Polyethylene has a refractive index of 1.52 in the mid-infrared region and a small number of absorption peaks, so it is useful for making optical filters in the mid-infrared region. Only 1 keV of energy is required to crosslink the entire film by irradiating an electron beam while depositing polyethylene. In addition, crosslinked polyethylene thin film has high mechanical strength, so there is no cracking or peeling when used with germanium. This allows for the use of crosslinked polyethylene as a low refractive index for mid-infrared optical coating. [ABSTRACT FROM AUTHOR]

The links students make among chemistry content is considered essential for a robust, enduring understanding in multiple learning theories. This article describes the development and implementation of an assessment technique, termed a Measure of Linked Concepts, designed to inform instructors on students' understanding of linking content throughout General Chemistry. Student performance on the assessment technique has provided unique insights relevant for instruction. For example, a substantial proportion of students could not identify when a model was used beyond its intended limit or show proficiency in tasks that the course assumed was prior knowledge. The use of these assessments also provides a means for instruction to show the relevance for topics such as periodic trends or ionic/molecular classification in a variety of subsequent topics throughout the course.

This study used a series of text message inquiries sent to General Chemistry students asking: "Have you studied for General Chemistry I in the past 48 hours? If so, how did you study?" This method for collecting data is novel to chemistry education research so the first research goals were to investigate the feasibility of the technique and the evidence for validity of the data collected. The results showed that text messages provide ample data on students' study habits though initial participant recruitment may pose a challenge. This study also explored evidence for validity and found that the percent of students reporting studying peaked with each exam date matching the expected trend (content validity) and participants in the study had only small departures from the population of students at the setting (generalizable validity). Second, students' study habits were characterized using cluster analysis finding three clusters: students that knowingly do not study, students who describe mandatory course components as studying and students who study in addition to the mandatory course components. These student groups were compared on a common exam in the course with the last group out-performing those who knowingly do not study. Finally, student study habits were charted across the semester and show signs of adapting, possibly as a result of course expectations or course content.

Spiral jet mills are ubiquitous in the pharmaceutical industry. Breakage and classification in spiral jet mills occur due to complex interactions between the fluid and the solid phases. The study of these interactions requires the use of computational fluid dynamics (CFD) for the fluid phase coupled with discrete element models (DEM) for the particle phase. In this study, we investigate particle dynamics in a 50-mm spiral jet mill through coupled CFD-DEM simulations. The simulations showed that the fluid was significantly decelerated by the presence of the particles in the milling chamber. Furthermore, we study the particle dynamics and collision statistics at two different operating conditions and three different particle loadings. As expected, the particle velocity was affected by both the particle loading and operating pressure. The particles moved slower at low pressures and high loadings. We also found that particle–particle collisions outnumbered particle–wall collisions.

Evaluating the impact of Chemistry Education Research articles has historically centered on the impact factor of the publishing journal. With the advent of electronic journal indices, it is possible to determine the impact of individual research articles by the number of citations it has received. However, in a relatively new discipline, such as Chemistry Education Research, it is necessary to provide context for the citation counts, particularly because Chemistry Education Research faculty are likely evaluated by chemistry faculty in more established subdisciplines. This study seeks to provide context by reviewing the citation counts for a sample of 749 Chemistry Education Research articles published in chemistry education or science education journals from 2007 through 2013. The number of citations was found to follow a non-normal distribution and, thus, results are presented using quartiles to describe the range of citations. The results are delineated by metric of citations (Web of Science and Google Scholar), year published, and in terms of established authors.

Considerable effort in chemistry education research has been dedicated to developing and evaluating reform pedagogies designed to improve student success in general chemistry. Policy recommendations propose adoption of these techniques as a means to increase the number of science graduates, however there is the potential that the impact of these reforms is mitigated in subsequent classes. This study examines the longitudinal impact of a successful peer-led team learning reform that targets general chemistry. The study uses a quasi-experimental methodology comparing students who took general chemistry with peer-led team learning to students who experienced traditional instruction. Student enrollment and academic performance in subsequent classes were the outcome metrics evaluated. The results found that the reform impacts enrollment in the class that directly follows the target class but enrollment in subsequent classes is mitigated through student attrition within the curriculum. Additionally, no evidence was found for the reform impacting students' academic performance in subsequent classes. The results highlight the need for implementing and evaluating curricular-wide reform.

Assumptive Learning Theory values the active process of linking concepts to promote meaningful over rote learning. To promote meaningful learning, assessment practices that encourage the linking of concepts need to be developed and utilized. Creative Exercises (CEs) have the potential to encourage such links. CEs are an open-ended assessment technique where students are given a single prompt and are asked to describe as many statements as they can that are distinct, correct, and relevant to the prompt. This study describes a qualitative investigation into student responses to CEs for evidence of students linking concepts throughout the course and the nature of the linked concepts. The findings indicate considerable interconnections of content in student responses. Further, students' efforts toward making connections revealed several misconceptions regarding their understanding of the limits of models. CEs are therefore proposed as a means to encourage students to link concepts and to inform instructors about the links made, both correctly and incorrectly. Finally, to determine the prevalence of the incorrect links, a novel assessment technique is proposed based on students' responses to CEs.

Validity of educational research instruments and student assessments has appropriately become a growing interest in the chemistry education research community. Of particular concern is an attention to the consequences to students that result from the interpretation of assessment scores and whether those consequences are swayed by invalidity within an assessment. This study examines external and consequential validity of a first-term general chemistry exam from the ACS Examinations Institute. The measure was used as a final exam in the intended course at the research setting. As a result, student performance on the exam contributed to the grading decision in the course. Owing to the prerequisite relationship, this grading decision then informed the decision to permit student enrollment in second-semester general chemistry. This study evaluates the appropriateness of the first-term general chemistry exam to inform this decision. Results indicate that the exam offers meaningful information into students' performance in the follow-on course with a consistent decision process across student subgroups.

Peer-Led Team Learning (PLTL) is a widely disseminated pedagogical reform that employs previously successful undergraduate students, peer leaders, to lead sessions of structured group work in the target class. Numerous studies have evaluated the impact of this reform in various post-secondary chemistry classes. Results from these studies suggest that PLTL may be effective at improving student success in these classes, either through improved performance on common exams or reduced student attrition in the classes. This study seeks to take a broader picture at measuring the impact, by examining the role PLTL plays across a two semester General Chemistry sequence. This includes an analysis of PLTL on students' decision to progress through the two semester sequence, and on PLTL impact on the algorithm-heavy second-semester General Chemistry. The findings suggest that the PLTL implementation is robust in improving student success directly in terms of the target class. However, PLTL had little to no effect on students' decision to continue in the General Chemistry sequence. Additionally, PLTL had little effect on student performance in subsequent courses where the pedagogy returned to lecture-only instruction. The results suggest that PLTL implementation on one course within a sequence would have limited impact, and in order to improve student progress toward graduation, PLTL implementation may have to be curricular wide. (Contains 5 tables.)

This study describes an evaluation of the Peer-Led Team Learning (PLTL) reform model in first-semester general chemistry. PLTL was implemented in place of one-third of the available lecture time, maintaining the same amount of structured class time under the reform. The evaluation demonstrates that classes implementing the PLTL reform at the setting featured a statistically significant improvement of 15% in the pass rate for the classes, compared to conventional, lecture-only classes at the same setting. Additionally, the PLTL classes maintained a comparable score on a comprehensive American Chemical Society final exam to that of the conventional classes. Combined, these findings suggest that the improvement in pass rates occurs while maintaining the same level of rigor in the PLTL classes. Examining student groups shows that students in underrepresented minority groups demonstrated the largest improvement in pass rates with the PLTL reform. (Contains 3 tables.)