Showing papers in "Journal of Chemical Education in 1998"
TL;DR: In this paper, a unique solar cell fabrication procedure has been developed using natural anthocyanin dyes extracted from berries, which can be reproduced with a minimum amount of resources in order to provide an interdisciplinary approach for lower-division undergraduate students learning the basic principles of biological extraction, physical chemistry, and spectroscopy as well as environmental science and electron transfer.
Abstract: A unique solar cell fabrication procedure has been developed using natural anthocyanin dyes extracted from berries. It can be reproduced with a minimum amount of resources in order to provide an interdisciplinary approach for lower-division undergraduate students learning the basic principles of biological extraction, physical chemistry, and spectroscopy as well as environmental science and electron transfer. Electron transfer is the basis of the energetics that drives the processes of life on Earth, occurring in both the mitochondrial membranes of living cells and in the thylakoid membranes of photosynthetic cells of green plants and algae (1). Although we depend on the petroleum and agricultural products of this electron and energy transfer, one of the greatest challenges of the 21st century is that we have yet to create devices that can be used to tap directly into the ultimate source of this energy on an economic scale. An experimental lab procedure was therefore created in order to illustrate the con...
306 citations
TL;DR: The method of fitting nonlinear functions with Solver is introduced and the treatment to weighted least squares and to the estimation of uncertainties in the least-squares parameters is extended.
Abstract: "Solver" is a powerful tool in the Microsoft Excel spreadsheet that provides a simple means of fitting experimental data to nonlinear functions. The procedure is so easy to use and its mode of operation is so obvious that it is excellent for students to learn the underlying principle of lease squares curve fitting. This article introduces the method of fitting nonlinear functions with Solver and extends the treatment to weighted least squares and to the estimation of uncertainties in the least-squares parameters.
237 citations
TL;DR: In this paper, the authors discuss several issues surrounding the development and use of instructional conceptual computer animations and suggest that an animation sequence should be linked to a lecture demonstration, thereby assisting in the presentation of all three levels of representation: microscopic, macroscopic and symbolic.
Abstract: Multimedia technology has advanced rapidly within the past two years providing an opportunity for chemistry instructors to develop and use their own computer animations. Conceptual computer animations are designed to help students understand the basic concept or principle of a dynamic chemical process. This paper discusses several issues surrounding the development and use of instructional conceptual computer animations. If possible, an animation sequence should be linked to a lecture demonstration, thereby assisting in the presentation of all three levels of representation: microscopic, macroscopic and symbolic. Computer animations provide instructors with a vehicle for presenting topics from the particulate nature of matter view and a technique for teaching for conceptual understanding. A design team consisting of individuals who have knowledge or expertise in the content area, instructional design, computer animation techniques, and graphic and sound production should work with the chemistry instructor...
168 citations
TL;DR: It can be shown that V/K actually provides a measure of the rate of capture of substrate by free enzyme into a productive complex or complexes destined to form products and complete a turnover at some later time.
Abstract: Most biochemistry textbooks describe V/K, or kcat/Km, as one of the fundamental kinetic constants for catalysis in enzymatic reactions and associate it with some measure of the rate of the chemical transformation of substrate into product. However, in the reactions of all enzymes except isomerases and mutases, V/K fails to encompass a complete turnover. Instead, it can be shown that V/K actually provides a measure of the rate of capture of substrate by free enzyme into a productive complex or complexes destined to form products and complete a turnover at some later time. Similarly, V or kcat provides a measure of the rate of release of product from the productive enzyme complexes that constitute capture. It is here suggested that the symbols V/K and kcat be replaced by kcap and krel, respectively, at least in the teaching of enzyme kinetics. Capture and release are equally necessary to generate a complete catalytic turnover, but they are determined by different things, and the proposed symbolism is less a...
163 citations
TL;DR: In this paper, a problem-based learning model was used to link art and chemistry through problembased learning activities, where students in class and teachers in professional development workshops become equally engaged in this chemistry unit.
Abstract: 33 ll artists are chemists. Artists understand and study the properties of specific materials and find ways to explore these properties to express views of themselves and the world around them. In this curriculum unit, chemistry students create an original artwork and describe the chemistry principles involved in their work. Before beginning the challenge, students learn the chemistry concepts and related art techniques through a series of eight activities. The five-week chemistry unit centers on the Artist as Chemist and uses a problem-based learning model. We have found that students in class and teachers in professional development workshops become equally engaged in this chemistry unit. As part of an NSF-supported curriculum project (Eisenkraft 2006), the project leans on the National Science Education Standards as Chemist Students link art and chemistry through problem-based learning activities
152 citations
TL;DR: The Workshop Chemistry model as discussed by the authors ) is a two-hour student-led workshop where students discuss and debate chemistry in a challenging but supportive environment, the connection to mentors and the power of working as part of a team.
Abstract: The Workshop Chemistry model embraces dimensions of student experience that are essential for learning: the freedom to discuss and debate chemistry in a challenging but supportive environment, the connection to mentors, and the power of working as part of a team. The workshop model calls for the traditional recitation, or a modest amount of lecture, to be replaced by a new curricular structure: a two-hour student-led workshop. In the first two and a half years of the project, more than 6000 students have participated in workshop courses in allied health, general, and organic chemistry, conducted by 27 faculty and more than 800 workshop leaders.
139 citations
TL;DR: The NSF Web site has a wealth of primary information on science and engineering, including education issues, and in late June they put online one of the best features yet: an "enhanced" version of the Web site.
Abstract: The NSF Web site has a wealth of primary information on science and engineering, including education issues. In late June they put online one of the best features yet: an "enhanced" version of the ...
89 citations
TL;DR: For example, the authors found statistically significant differences in test scores based on gender, showing that males scored higher than females, while females performed better than males on a subset of twelve questions representing visualization abilities.
Abstract: General chemistry students in four different courses spanning a 12-year period were given a paper-pencil reasoning test entitled An Inventory of Piagetian Developmental Tasks (IPDT). A subset of twelve questions from this test, representing visualization abilities, were used to investigate spatial perceptual skills of students with regards to gender and course level. These findings indicate statistically significant differences in test scores based on gender, showing that males scored higher than females. A longitudinal study, comparing data from the early 1980's to data from the 1990's reveals an eroding of IPDT scores in students enrolled in the general chemistry course at Southeast Missouri State University. Gender-related scores over the same time period show a decrease in the gender gap due to a lowering of male scores. Possible explanations of results and further areas of study are suggested in the context of spatial perception research.
88 citations
TL;DR: In fact, in most cases the mixing process is exothermic, so the immiscibility of the two liquids must be explained by a loss of entropy in the system as mentioned in this paper.
Abstract: The majority of introductory chemistry and organic chemistry textbooks state that oil and water don't mix because of enthalpic effects. These texts generally make the argument that the mixing process is endothermic, reasoning that the water-water hydrogen bonds that must be broken in order to accommodate the solute are much stronger than the subsequent solvent-solute dipole-induced dipole intermolecular forces that are formed. In fact, in most cases the mixing process is exothermic, so the immiscibility of the two liquids must be explained by a loss of entropy in the system. The widely accepted model explaining the hydrophobic effect invokes the formation of icelike clathrate hydrate "cages" around nonpolar solute molecules. Water molecules at the surface of these relatively rigid clathrate structures are strongly hydrogen-bonded to one another. The formation of these solvent "cages" explains why both Delta H and Delta S are negative for the solution process, and the endergonicity of solvation is thus due to entropy and not enthalpy. Authors should remove from their textbooks the incorrect enthalpic/hydrogen-bond explanation for the hydrophobic effect. Because aspects of the correct entropic/clathrate "cage" explanation lie beyond the scope of introductory or organic chemistry courses, it may be wisest to omit any detailed physical explanation of the "like dissolves like" phenomenon. If the overall format of the text permits, a brief discussion of solvation entropy effects might be included in the section dealing with the immiscibility of oil and water
87 citations
TL;DR: The first part of a three-part series based on the author's keynote lectures for the 1995 NEACT conference as mentioned in this paper addresses the question of how the various concepts and models of chemistry are interrelated and proposes a nine-category classification based on whether the concept or model in question deals with the structure/composition, the energy, or the time dimension of chemistry.
Abstract: The first of a three-part series based on the author's keynote lectures for the 1995 NEACT conference, this lecture addresses the question of how the various concepts and models of chemistry are interrelated and proposes a nine-category classification based on whether the concept or model in question deals with the structure/composition, the energy, or the time dimension of chemistry, and whether the concept or model does so at the molar, molecular, or electrical level of chemical discourse.
75 citations
TL;DR: The second part of a three-part series based on the author's keynote lectures for the 1995 NEACT conference as mentioned in this paper applies the classification of chemical concepts and models given in Lecture I to
Abstract: The second of a three-part series based on the author's keynote lectures for the 1995 NEACT conference, this lecture applies the classification of chemical concepts and models given in Lecture I to
TL;DR: In this article, a two-day laboratory experiment describes how the influence of the hydrocarbon chain length and added salt on the micellar aggregation number of ionic surfactants can be investigated by steady-state fluorescence measurements.
Abstract: This two-day laboratory experiment describes how the influence of the hydrocarbon chain length and added salt on the micellar aggregation number of ionic surfactants can be investigated by steady-state fluorescence measurements. Emphasis is put on the necessity to validate the models used to evaluate the data, and examples are given when a given model does not work.
For the effect of added salt, sodium dodecylsulphate with and without added sodium chloride was investigated. Both quenchers used, i.e., dodecylpyridinium chloride (DoPyrCl) and 1,3-dicyanobenzene (DCB), yield aggregation numbers in agreement with literature values.
For the effect of surfactant chain length, however, the used model failed under certain circumstances. Three alkyltrimethylammonium halides were investigated (CnTA+; n=12, 14, and 16). For the shortest one, DoPyrCl yields a good aggregation number while DCB fails due to electrostatic interactions. For the tetradecyl surfactant, DoPyrCl does not work well, as the difference between the tail-lengths of the quencher and surfactant causes problems in the determination of the amount of micelle-bound quencher. Tetradecylpyridinium chloride circumvents this problem and a consistent aggregation number is obtained. Finally, for the longest surfactant, not even a quencher with a tail of equal length of the surfactant's worked out well, due to the slow diffusion of the quencher in the micellar aggregate.
TL;DR: In this article, a new strategy has been developed to credibly assess the effects of curriculum reform on student competence, and a comparative assessment was performed between the two strategies in order to implement the strategy.
Abstract: A new strategy has been developed to credibly assess the effects of curriculum reform on student competence. In order to implement the strategy, a comparative assessment was performed between the s...
TL;DR: In this paper, an iron electrode (paper clip) is used in conjunction with pH indicator dyes, so dramatic color changes will be noticed, and the experiment is shown to be effective in removing colloidal particles.
Abstract: Due to the large production of aqueous waste streams from textile mills and dye production plants, several processes have been under intense study. Electrochemical processes offer some distinctive advantages, including effects due to: 1) the production of electrolysis gases, and 2) the production of polyvalent cations from the oxidation of corrodible anodes (like Fe and Al). The gas bubbles can carry the pollutant to the top of the solution where it can be more easily concentrated, collected and removed. The metallic ions can react with the OH- ions produced at the cathode during the evolution of H2 gas to yield insoluble hydroxides that will adsorb pollutants out of the solution and also contribute to coagulation by neutralizing any negatively charged colloidal particles that might be present. In this experiment an iron electrode (paper clip) is used in conjunction with pH indicator dyes, so dramatic color changes will be noticed.
TL;DR: A PST problem is an interactive situation in which a student has to assume his or her responsibility in gathering, assimilating, and exchanging new information in a group as discussed by the authors, and it is structured so that it presents the student a "puzzle"; it cannot be solved readily by activation of a student's previous knowledge.
Abstract: The traditional "Cookbook-formula-experiments" do not develop student's scientific initiative, or creativity in the chemistry laboratory. Information is better understood, retained and transfered when the student elaborates it.A PST problem is an interactive situation in which a student has to assume his or her responsibility in gathering, assimilating and exchanging new information in a group. It is structured so that it presents the student a "puzzle"; it cannot be solved readily by the activation of a student's previous knowledge.PST Summary.First two weeks - -Each team of 3 students identifies and distributes among its members the different parameters and the laboratory procedures elaborated to solve the problem. -Each student experiments one of the 3 different pilot procedures elaborated by his team and exchanges results with team mates. Each team chooses a procedure .Third week -During this exam period each student experiments the procedure chosen, or synthesize a compound imposed by the professor.F...
TL;DR: In this paper, the authors show experimental evidence for the dynamic character of surfaces during chemical processes, showing that the surface restructures and the metal atoms move into new sites, dictated by the chemisorption bond so as to optimize the strength of that bond, thereby creating the active sites for surface chemical processes.
Abstract: Modern surface chemistry has made significant contributions to the molecular level understanding of macroscopic surface phenomena including adsorption, bonding, catalysis and tribology. According to the classical view, surface atoms are rigid and occupy equilibrium sites dictated by the bulk unit cell. Modern surface science techniques that permit atomic scale monitoring of the structures of both the surface atoms and adsorbates during surface processes have shattered the myth of the rigid surface. A new model of the surface has been adopted, the so-called flexible surface. Upon adsorption the surface restructures and the metal atoms move into new sites, dictated by the chemisorption bond so as to optimize the strength of that bond, thereby creating the active sites for surface chemical processes. In this paper we show experimental evidence for the dynamic character of surfaces during chemical processes. First a historical perspective is presented and basic concepts such as surface concentration and dispe...
TL;DR: In addition to the traditional lecture format, three other teaching strategies (class discussions, concept maps, and cooperative learning) were incorporated into a freshman level general chemistry course as mentioned in this paper, and student perceptions of their involvement in each of the teaching methods, as well as their perceptions of the utility of each method were used to assess the effectiveness of the integration of teaching strategies as received by the students.
Abstract: In addition to the traditional lecture format, three other teaching strategies (class discussions, concept maps, and cooperative learning) were incorporated into a freshman level general chemistry course. Student perceptions of their involvement in each of the teaching methods, as well as their perceptions of the utility of each method were used to assess the effectiveness of the integration of the teaching strategies as received by the students. Results suggest that each strategy serves a unique purpose for the students and increased student involvement in the course. These results indicate that the multiple teaching strategies were well received by the students and that all teaching strategies are necessary for students to get the most out of the course.
TL;DR: Carbonless copy paper, used to make countless copies of forms, is a 109 kg business annually as discussed by the authors, and copies are made when the pressure of a pen ruptures microcapsules that contain a dye precursor.
Abstract: Carbonless copy paper, used to make countless copies of forms, is a 109 kg business annually. Copies are made when the pressure of a pen ruptures microcapsules that contain a dye precursor, initiat...
TL;DR: In this article, a photochemical experiment involving the photochemical dimerization of anthracene, characterization of the product by UV, IR and NMR spectroscopy, and thermolysis of the dimer was described.
Abstract: A photochemical experiment is described which requires only common laboratory equipment. The experiment involves the photochemical dimerization of anthracene, characterization of the product by UV, IR and NMR spectroscopy, and thermolysis of the dimer.
TL;DR: The authors discusses how misconceptions can cluster and compound in science education and how to cluster them and compound them in the course of a science education course, using qualitative and quantitative research in the field.
Abstract: Recent, qualitative research in science education has uncovered many naive or incorrect ideas about aspects of science commonly held by students and others at all levels. This article discusses how misconceptions can cluster and compound.
TL;DR: In this article, an early-stage synthesis of aspirin starting from oil of wintergreen is described. But, unlike traditional aspirin synthesis experiments, it is designed to be performed early rather than late, and it requires two steps rather than one.
Abstract: An experiment is described that is suitable for the early portion of the laboratory in a general chemistry course and integrates organic examples. It is the two-step synthesis of aspirin starting from oil of wintergreen. The mechanism for this synthesis provides examples of three major classes of chemical reactions: hydrolysis, condensation, and proton transfer. To understand the chemistry, the student must be able to recognize the common molecular framework shared by oil of wintergreen, salicylic acid, and aspirin and to identify the -OH and -CO2 sites where chemical changes occur. The experiment differs in three ways from traditional aspirin synthesis experiments for general chemistry. It is designed to be performed early rather than late; it starts from a naturally occurring material and requires two steps rather than one; and it utilizes FTIR spectroscopy to distinguish among oil of wintergreen starting material, salicylic acid intermediate, and aspirin product. The use of FTIR spectroscopy introduces...
TL;DR: A polymer demonstration involving the crosslinking and decrosslinking of alginate, a polysaccharide isolated from seaweed, is described in this article. But it is not shown in this paper.
Abstract: We have recently devised a polymer demonstration involving the crosslinking and decrosslinking of alginate, a polysaccharide isolated from seaweed. The polymer is composed of D-mannuronic acid and L-guluronic acid subunits and is a component of cell walls. It is commonly used as a thickener in foods such as ice cream and fruit-filled snacks. For the demonstration, a 2% solution of sodium alginate is poured into a 1% solution of calcium chloride. Nontoxic calcium alginate "worms" form due to crosslinking of the polymer. Alternatively, the commercially available antacid Gaviscon can be used as a source of sodium alginate. The crosslinks can then be broken by shaking the worms in brine. The demonstration is a fine addition to any chemical educator's repertoire of polymer experiments.
TL;DR: In this paper, an intervention program for teaching chemistry through history was developed to determine whether this instructional approach would promote conceptual problem-solving ability of secondary school students, and the qualitative results of interviews indicated that students have learned from the history of science to avoid alternative conceptions held by previous scientists.
Abstract: An intervention program for teaching chemistry through history was developed to determine whether this instructional approach would promote conceptual problem-solving ability of secondary school students. Three chemistry teachers and five classes of 8th graders (N = 220) participated in this quasi-experimental study. The quantitative results of a conceptual problem-solving test revealed that the experimental group students outperformed their counterparts in both the control and the comparison groups. In addition, low achievers benefited more from this teaching strategy than high achievers. The qualitative results of interviews indicated that students have learned from the history of science to avoid alternative conceptions held by previous scientists.
TL;DR: In this paper, the status of laboratory-based instruction in chemistry at the beginning college level for majors and non-majors is investigated in 16 institutions of higher education located throughout 5 states in the Northeast region of the U.S.
Abstract: The authors report on one of a series of studies related to seeking a more effective role for laboratory experience in science instruction. This particular study addresses the status of laboratory based instruction in chemistry at the beginning college level for majors and nonmajors. The study is of interest to those who seek effective means of reforming beginning college level chemistry instruction in ways that give greater emphasis to laboratory based experiences.The study sample consists of 24 college chemistry instructors, and 3000 students from 24 laboratory sessions in 16 institutions of higher education (IHE) located throughout 5 states in the Northeast region of the U.S. An additional IHE in Germany was included for purposes of comparison because of the knowledge that the approach to chemistry instruction in Germany differed substantially from those practiced in the U.S.Pre-, post and actual laboratory sessions were videotaped. Teaching behaviors were analyzed and categorized using the validated M...
TL;DR: Cooperative learning is not simply putting students into groups and telling them to work together as mentioned in this paper, but rather it requires preparation on the part of the students and the instructor, which can improve team problem solving skills and promote the development of interpersonal skills and communication skills.
Abstract: The American Chemical Society Committee on Professional Training presented in their Spring 1996 newsletter the results of an industrial roundtable which was convened to address what industry looks for in new hires. Roundtable participants voiced broad agreement that in addition to technical skills, one of the key experiences industry seeks in new hires is team problem solving. Cooperative learning activities improve team problem solving skills and promote the development of interpersonal skills and communication skills through face-to-face interactions.Cooperative learning is not simply putting students into groups and telling them to work together. Cooperative learning requires preparation on the part of the students and the instructor. This article discusses how to implement cooperative learning through a series of activities which allow the students to get to know each other. Students who build supportive committed relationships with each other become more committed to the course, more committed to eac...
TL;DR: Bioorganic approach for students interested in the life sciences and in health care fields as mentioned in this paper is a bioorganic approach that is suitable for both students and adults interested in bio-engineering.
Abstract: Bioorganic approach for students interested in the life sciences and in health care fields.
TL;DR: In this article, the Nernst equation was applied to the cyclic voltammetry of Prussian Blue (PB) deposited onto a transparent electrode to evaluate the dependence of the ratio of oxidized to reduced states on the electrode with the applied potential.
Abstract: The electrochemical behavior of Prussian Blue (PB) deposited onto a transparent electrode is specially attractive to students beginning their laboratory experiences in Electrochemistry. The color changes observed during the cyclic voltammetry facilitate the qualitative introduction of such important electrochemical topics as the dependence of composition (ratio of oxidized to reduced state) on the electrode with the applied potential (Nernst equation). The experiment also introduces the student to the measurement of electrochemical magnitudes (peak potential, peak current, half-peak width) for the voltammogram. The knowledge of an electrochemical technique as important as the cyclic voltametry is also of interest to students, due to its application in several fields such as corrosion, electroanalysis, heterogeneous catalysis, characterization of materials, or electrochemical kinetics.The electrogeneration of Prussian Blue, potentiostatically or galvanostatically, makes possible the correlation between the...
TL;DR: The New Traditions Consortium as discussed by the authors was created by faculty from two-year colleges, liberal arts colleges, comprehensive universities, and research universities who are united by the common goal of effecting paradigm shifts in the chemistry learning experience.
Abstract: The New Traditions Consortium comprises faculty from two-year colleges, liberal arts colleges, comprehensive universities, and research universities who are united by the common goal of effecting paradigm shifts in the chemistry learning experience. The primary sites of New Traditions activity have been Madison Area Technical College, College of the Holy Cross, Franklin and Marshall College, San Jose State University, University of Illinois - Urbana-Champaign, and University of Wisconsin-Madison. Individuals from a number of other institutions have contributed. Our approach has been to identify mechanisms of pedagogical/instructional change, implement them at different types of institutions, and evaluate their effects on student learning.
TL;DR: The agreement between actual solubility and simple calculations of solubilities from Ksp values has been questioned many times as mentioned in this paper, as incomplete dissociation, hydrolysis reactions, complex ion formation and activity coefficients conspire to make such calculations crude at best.
Abstract: The calculation of solubility from Ksp values, and its converse have long been a part of general college chemistry textbooks. The agreement between actual solubility and simple calculations of solubility from Ksp values has been questioned many times. Incomplete dissociation, hydrolysis reactions, complex ion formation, ion pair formation and activity coefficients conspire to make such calculations crude at best.The authors sought to find those cases of partly soluble substances for which simple calculations such as Ksp=S2, and Ksp=4S3 can realistically be used for computing solubility from Ksp and the reverse calculation. Empirical solubility data are compared with solubilities calculated from reliable Ksp values that have been adjusted for activity coefficients. A table of 18 substances is suggested for textbook use.