Showing papers in "Journal of Chemical Education in 2005"

Departing from Lectures: An Evaluation of a Peer-Led Guided Inquiry Alternative

Abstract: To improve a large-enrollment general chemistry course based on conventional lectures, we instituted a reform combining peer-led team learning with a guided inquiry approach, together called peer-led guided inquiry (PLGI). For one group of first-semester general chemistry students, a PLGI session was combined with two lectures per week, and this group was compared to a control group that had the usual three lectures per week. Students were compared based on performance on identical course exams and on a final exam from the ACS Examinations Institute given at the end of the semester. The experimental group was found to perform better than the control group overall, in spite of experiencing one fewer lecture each week. Also, attendance at the PLGI sessions was found to have a significant positive impact on student performance, even when controlling for students’ SAT mathematics and verbal scores. This method of evaluating reform effects for institutions with several large sections of introductory chemistry ...

"It Gets Me to the Product": How Students Propose Organic Mechanisms

Abstract: The ability to use the curved-arrow or electron-pushing formalism is one of the most vital skills in the organic chemist's repertoire. Their introduction to this formalism occurs when they first encounter reaction mechanisms. As they gain experience, the arrow-pushing formalism eventually becomes the primary technique organic chemists use to do retrosynthetic analysis, to predict the chemoselectivity of a reaction, and to create novel methodologies. Because practicing organic chemists use the arrow-pushing formalism in situations that are far removed from the simple contexts in which they are first presented, this study probed how students enrolled in a first-semester, graduate-level organic chemistry course approached the task of writing the mechanisms for two- to four-step reactions that lacked the typical cues that bring common mechanisms to mind. This article focuses on the students' solutions and discusses possible limitations of their strategies.

A safer, easier, faster synthesis for CdSe quantum dot nanocrystals

Abstract: Properties that vary with particle size are an important feature of nanoscale materials. CdSe quantum dot nanocrystals vary in color from green–yellow to orange–red and luminesce from blue to yellow, where shorter wavelength, higher energy, electronic transitions correspond to smaller particle sizes. CdSe quantum dot nanocrystals are a visually engaging way to demonstrate quantum effects in chemistry, since their transition energies can be explained as a "particle in a box", where a delocalized electron is the particle and the nanocrystal is the box. Following the method pioneered by Xiaogang Peng and coworkers, CdSe nanocrystals are synthesized from CdO, oleic acid, elemental Se, and trioctylphosphine using a kinetic growth method in octadecene at 225 °C and a less than three-minute reaction time. This synthesis has several advantages over methods using dimethyl cadmium, a chemical that is extremely toxic, expensive, unstable, pyrophoric, and requires inert atmosphere techniques. When excited at 400 nm, ...

STOCKHOLM CONVENTION and Persistent Organic Pollutants (POPs)

Abstract: In this paper, the characteristics of POPs are given. The kind, structure, usage and harm of twelve POPs inhibited by STOCKHOLM CONVENTION are introduced. In addtion, the status of POPs in China is also given.

Beyond "Student Attitudes": Chemistry Self-Concept Inventory for Assessment of the Affective Component of Student Learning

Abstract: The development of a 40-item Likert-style assessment instrument for measuring student self-concept as a learner of chemistry is described. Developed for college-student populations, the Chemistry Self-Concept Inventory has subscales that pertain to chemistry learning, mathematics learning, academics in general, academic enjoyment, and creativity. Detailed information on validity is provided by means of exploratory factor analysis, comparisons between different populations of students (general chemistry, undergraduate peer leaders, and chemistry majors), and comparison with course performance. Reliability is established by estimation of internal consistency of subscales and retesting correlation. The importance of establishing psychometric characteristics is argued using chemical analysis analogies. The Chemistry Self-Concept Inventory is broadly applicable in any curriculum setting for assessing longitudinal change or for drawing comparisons among curriculum structures.

Experiences and Reflections about Teaching Atomic Structure in a Jigsaw Classroom in Lower Secondary School Chemistry Lessons

Abstract: This article describes and discusses an example of how atomic structure can be taught in lower secondary chemistry using a modified jigsaw-classroom method. The lesson was taught in grades 9 and 10 (age range 15–17 years) chemistry in 13 learning groups with a total of 313 students in various grammar, middle, and comprehensive schools in Germany. The written evaluation of the lesson focused on determining the students’ opinions on the teaching methods that were used. Emphasis was on gathering information from the students’ viewpoint. Did the students think that these methods could make science lessons more attractive? Could these methods help to promote more active student learning, cooperative learning, or communicative and social abilities? Additional data that were derived from a cognitive test and teacher feedback are also presented. The results of the study show that teaching methods like the jigsaw classroom have potential to improve students’ attitude towards science. The results may also indicate ...

Template Synthesis and Magnetic Manipulation of Nickel Nanowires

Abstract: In this experiment students prepare nickel nanowires using a template synthesis technique and characterize their properties. Electrodeposition of nickel to fill the 200-nm diameter pores of a commercially-available alumina filtration membrane is accomplished using a nickel salt solution and a AA battery. The nanowires, which are ~200 nm in diameter and up to ~50 I¼m in length, can be liberated from the membrane by dissolving the alumina template with sodium hydroxide. Suspensions of nanowires on a microscope slide can be observed using a common optical microscope. The alignment and movement of the magnetic nanowires can be controlled using magnets. This experiment is appropriate in introductory college chemistry courses and in upper-level physical and inorganic chemistry courses. The experiment provides students with a hands-on laboratory experience in nanotechnology, while illustrating fundamental ideas from a variety of areas, including electrochemistry, magnetism, and materials science.

Cholesterol and Plants

Abstract: Current textbooks give an inaccurate picture of the occurrence of cholesterol in plants and also of the role of plant sterols in the mammalian uptake of cholesterol.

Evaluating Students' Conceptual Understanding of Balanced Equations and Stoichiometric Ratios Using a Particulate Drawing

Abstract: A total of 156 students were asked to provide free-response balanced chemical equations for a classic multiple-choice particulate-drawing question first used by Nurrenbern and Pickering. The balanced equations and the number of students providing each equation are reported in this study. The most common student errors included a confusion between the concepts of subscripts and coefficients and including unreacted chemical species in the equation. Equations consistent with two of the five choices used in Nurrenbern and Pickering’s question appeared in this study, but none of the students provided balanced equations consistent with the other three distractors. Suggestions for better distractors are provided in this paper. The students were also asked to perform two stoichiometric calculations using the balanced equation they generated. These responses were evaluated to determine whether the students had a grasp of simple stoichiometric calculations and the reacting ratios of the two starting materials. Stud...

Student opinions regarding inquiry-based labs

Abstract: A survey of high school chemistry teachers in the U.S. indicated that 45.5% of these teachers are not using inquiry methods in their classroom. Perhaps they would be persuaded by student insights into learning with inquiry. This article describes the positive and negative sides of including inquiry laboratories in science classrooms. Student quotes are used to illustrate both benefits and drawbacks of the inquiry method.

Chemistry of Durable and Regenerable Biocidal Textiles

Abstract: Unlike the widely used slow-releasing biocidal mechanism now employed in biocidal textiles, a novel regenerable process, based on a regeneration principle and halamine chemistry, has been developed in antimicrobial finishing of textiles. Halamine-modified textile materials demonstrate durable and regenerable antimicrobial functions and execute rapid inactivation of a broad spectrum of microorganisms by contact without yielding drug resistance. The unique properties of the products render them useful materials for medical-use and hygienic textiles. The chemistry of the biocidal materials is be discussed.

The "Virtual ChemLab" Project: A Realistic and Sophisticated Simulation of Organic Synthesis and Organic Qualitative Analysis

Abstract: In the past four years we have created a set of sophisticated and realistic laboratory simulations for use in freshman- and sophomore-level chemistry classes and laboratories called Virtual ChemLab. We have completed simulations for Inorganic Qualitative Analysis, Organic Synthesis and Organic Qualitative Analysis, Fundamental Experiments in Quantum Chemistry, Gas Properties, Titration Experiments, and Calorimetry. The purpose of our simulations is to reinforce concepts taught in the classroom, provide an environment for creative learning, and emphasize the thinking behind instructional laboratory experiments. We have used the inorganic and organic simulations extensively with thousands of students in our department at Brigham Young University. Some important learnings from our evaluation include: (i) students enjoy using these simulations and find them to be an asset in learning effective problem-solving strategies, (ii) students like the fact that they can both reproduce experimental procedures and expl...

Attitudinal Effects of a Student-Centered Active Learning Environment

Abstract: The importance of attitudes toward science has risen from widely accepted assumptions that achievement and attitude are positively interdependent and that affective variables are as important as cognitive variables in molding student learning. This report examines the effect on student attitudes toward learning chemistry in an active learning environment that has incorporated elements believed to positively influence student attitudes toward science including cooperative learning, hands-on activities, real-world applications, and engaging technology. These elements were considered for synergetic effects and not as individual contributors to the overall results. Two different sections of the same general chemistry course participated. The lecture setting was used as the control. Residualized gain scores were used to compare net changes in student attitudes. Data were analyzed for possible differences in gain for different academic majors. Anxiety in chemistry was monitored for the two class settings in thr...

Growth Kinetics and Modeling of ZnO Nanoparticles

Abstract: This article describes a method to measure the growth kinetics of a zinc oxide colloid. Using common instrumentation such as UV–vis spectroscopy, the cut-off wavelength can be determined and hence, the particle size can be estimated. Using existing models of colloidal nanoparticle properties, the absorbance is modeled and compared to the experimental curves. The effect of different parameters in the model such as particle size, refractive index, and solvent type are investigated and conclusions drawn about the nature of nanoparticulate systems.

Just Click It: Undergraduate Procedures for the Copper(I)-Catalyzed Formation of 1,2,3-Triazoles from Azides and Terminal Acetylenes

Abstract: A procedure for copper(I)-catalyzed triazole synthesis using azides and terminal acetylenes introduces undergraduate organic students to the growing world of click chemistry. The reaction is ideal for the undergraduate laboratory as, in keeping with the defining aspects of click chemistry, it is high-yielding, requires no chromatography, is easily monitored by TLC, and displays distinct peaks in both IR and 1H-NMR. Virtually all products precipitate, and with just a few different starting blocks every student, or pair of lab partners, can produce a unique "clicked" compound. Additionally, general procedures for in situ azide synthesis and phenol propargylation provide a vehicle for chemical discovery and creativity well beyond the mini-libraries presented.

Relativistic Effects and the Chemistry of the Heaviest Main-Group Elements.

Abstract: This chapter reviews possible experimental aspects of relativistic effects in heavier Main Group elements and their compounds. Attention is focused on the sixth, sev- enth and eighth Period elements, for which the relativistic contribution to their physical and chemical properties is significant. Superheavy elements through Z D 120 are also discussed. This review may increase interest of theoreticians in chemistry-oriented problems that require use of relativistic methods of quantum chemistry.

Thermodynamics of the Relationship between Lattice Energy and Lattice Enthalpy

Abstract: Incorporation of lattice potential energy, UPOT, within a Born–Fajans–Haber thermochemical cycle based on enthalpy changes necessitates correction of the energy of the lattice to an enthalpy term, ΔHL For a lattice containing si ions of type i in the formula unit, the lattice enthalpy is given by ΔHL = UPOT + ∑si[(ci/2) - 2]RT where R is the gas constant (= 8314 J K-1 mol-1), T is the absolute temperature, and ci is defined according as to whether the ion i is monatomic (ci = 3), linear polyatomic (ci= 5), or polyatomic (ci= 6), respectively

Using an Interactive, Compensatory Model of Learning to Improve Chemistry Teaching.

Abstract: Many college chemistry teachers have little or no formal training in education. When issues related to education are discussed, these teachers are confronted with an array of apparently conflicting information, practices, and ideas. A speculative model, the interactive compensatory model of learning (ICML), is based upon a synthesis of the very diverse education research literature. It conceptually unifies seemingly conflicting elements. The model suggests: (a) many skills make important contributions to learning; (b) no single skill can support totally or interfere with self-regulated learning; (c) effective learning depends on the dynamic interrelationship among existing knowledge, including a variety of learning skills; (d) it is possible for most learners to compensate for weaknesses in one area using strengths in other areas; and (e) it is possible to improve skills through classroom instruction. This paper describes the model and offers practical suggestions. Supplemental materials provide additiona...

A Sensitive Nitrate Ion-Selective Electrode from a Pencil Lead. An Analytical Laboratory Experiment

Abstract: Nitrate ion is an important environmental and human health analyte and thus its detection and quantification is considered essential. This article summarizes a simple procedure for preparing and testing a nitrate ion-selective electrode based on doped polypyrrole films. Everyday pencil leads were used as a substrate for the electrochemical deposition of polypyrrole. Nitrate-doped polypyrrole electrodes, tested potentiometrically for their response to varying NO3–concentrations, exhibited Nernstian behavior (slopes of 54–55 mV per log cycle of nitrate concentration at T = 22°C), with a linear response to nitrate concentrations spanning three orders of magnitude (0.1–1× 10–4 M of NO3–) and a detection limit of 5 ± 1 × 10–5 M of nitrate. The procedure outlined here has the potential to initiate and motivate students with interests in sensor development, micro-fabrication procedures, advanced monitoring of environmental problems, and creating solutions to those problems.

Going Green: Lecture Assignments and Lab Experiences for the College Curriculum

Abstract: This paper provides an overview of green chemistry, including ways to incorporate green chemistry principles in existing courses and laboratories. Green chemistry experiments previously published in this Journal are listed.

Connected Chemistry—A Novel Modeling Environment for the Chemistry Classroom

Abstract: This article introduces a novel learning environment for teaching chemistry, Connected Chemistry, and describes its potential use in a high school and undergraduate chemistry classrooms. Connected Chemistry comprises several molecular simulations and is designed to enable instructors to teach chemistry using the perspective of "emergent phenomena". That is, it allows students to see observed macro-level chemical phenomena, like many other scientific phenomena, as resultant from the interactions of many individual agents on a micro-level. This perspective is especially appropriate to the study of chemistry where the interactions between multitudes of molecules on the atomic level give rise to the macro-level concepts that students study in the classroom. For example, physical processes such as melting and evaporation and the concepts of pressure and temperature result from such molecular interactions, which students cannot observe directly. Modeling environments such as Connected Chemistry provide students...

Assessing the Effect of Web-Based Learning Tools on Student Understanding of Stoichiometry Using Knowledge Space Theory

Abstract: This paper reports a comparative study using knowledge space theory (KST) to assess the impact of a Web-based instructional software program on students' understanding of the concept of stoichiometry. The software program called Mastering Chemistry Web (MCWeb) allows students to practice problems that emphasize the development of molecular-level conceptualization and visualization, analytical reasoning, and proportional reasoning, as well as learning to recognize and relate different representations in chemistry. The experimental design compared students in two sections taught by the same instructor. One section used the MCWeb instructional software as homework (MCWeb group) while the other section used text-based homework (non-MCWeb group, control). Several assessments revealed significantly better performance by the students in the MCWeb group over the control group whether measured in terms of in-class exams, conceptual versus algorithmic tests, or a KST test to assess the ability to make connections b...

Techniques To Enhance Instructors' Teaching Effectiveness with Chemistry Students Who Are Blind or Visually Impaired

Abstract: This paper describes techniques developed as solutions to problems encountered while teaching blind or visually impaired students in chemistry courses at high school and postsecondary levels. Establishing and maintaining a sound student–instructor relationship is critical to the success and implementation of a plan of action for blind or visually impaired students enrolled in chemistry courses.

The Chemistry of Coffee

Abstract: The molecules associated with coffee (including trigonelline, 2,4,6-trichloroanisole, nicotinic acid, and chlorogenic acid) demonstrate a range of structural features that students will benefit from examining in three dimensions.

A Comparison Study: Assessing Teachers' Conceptions with the Chemistry Concepts Inventory

Abstract: "Science as inquiry" is a key component of the National Science Education Standards. A deep conceptual understanding of chemistry is critical to the successful implementation of inquiry-based lessons. In this paper we report the results of a study to assess alternate conceptions of teachers in a large urban district—many of whom are teaching out-of-discipline—to further inform professional development activities related to the adoption of a reform-based chemistry curriculum. Teacher responses to the Chemistry Concepts Inventory were analyzed to assess alternate conceptions, and correlations were made to previously reported alternate conceptions of entering college students. The teachers scored higher than students on all items, however, the teachers' answers generally demonstrated a distribution similar to students of most commonly incorrect items and alternate conceptions, most of which involved translating between macroscopic, microscopic, and symbolic representations. Potential origins and impacts of t...

Isolation of Shikimic Acid from Star Aniseed

Abstract: The isolation of shikimic acid from star aniseed is described. This experiment uses Soxhlet extraction followed by ion exchange chromatography to isolate crude shikimic acid from the star aniseed. Subsequent charcoal decolorization and recrystallization from toluene and methanol afford the pure shikimic acid in 2–7% w/w yield.

Pharmaceutical Applications of Ion-Exchange Resins

Abstract: The historical uses of ion-exchange resins and a summary of the basic chemical principles involved in the ion-exchange process are discussed. Specific applications of ion-exchange resins are provided. The utility of these agents to stabilize drugs are evaluated. Commonly occurring chemical and physical incompatibilities are reviewed. Ion-exchange resins have found applicability as inactive pharmaceutical constituents, particularly as disintegrants (inactive tablet ingredient whose function is to rapidly disrupt the tablet matrix on contact with gastric fluid). One of the more elegant approaches to improving palatability of ionizable drugs is the use of ion-exchange resins as taste-masking agents. The selection, optimization of drug:resin ratio and particle size, together with a review of scaleup of typical manufacturing processes for taste-masked products are provided. Ion-exchange resins have been extensively utilized in oral sustained-release products. The selection, optimization of drug:resin ratio and...

Making Usable, Quality Opaque or Transparent Soap.

Abstract: First-year and organic chemistry students will learn the chemistry of soap by making some of the eleven described formulations, which produce usable, quality bars of soap. Opaque and transparent soaps are made in two and three hours, respectively. With an introduction to formulation chemistry, organic chemistry students can devise a formulation to synthesize their own opaque soap. Many of the formulations use commonly-available fats and oils, while some formulations incorporate specialty fats and oils for therapeutic purposes, for example, to relieve dry skin or itching. After one week of curing, the effectiveness of the prepared soap and commercially-available surfactants are tested in hard and soft water. The pH of the prepared soap, commercial surfactants, and the students' skin are measured and compared. In laboratory sections where students make soaps from different formulations, students can wash their hands with a bar of each and compare the quantity and quality of lather, the size of the bubbles, ...

Service-Learning in Introductory Chemistry: Supplementing Chemistry Curriculum in Elementary Schools

Abstract: The pedagogy of service-learning is becoming an accepted method of connecting college classrooms to the community. A service-learning course component has been successfully incorporated into the se...

A Supramolecular Approach to Medicinal Chemistry: Medicine Beyond the Molecule

Abstract: This article focuses on the essential roles played by intermolecular forces in mediating the interactions between chemical molecules and biological systems. Intermolecular forces constitute a key topic in chemistry programs, yet can sometimes seem disconnected from real-life applications. However, by taking a "supramolecular" view of medicinal chemistry and focusing on interactions between molecules, it is possible to come to a deeper understanding of recent developments in medicine. This allows us to gain a real insight into the interface between biology and chemistry—an interdisciplinary area that is crucial for the development of modern medicinal products. This article emphasizes a conceptual view of medicinal chemistry, which has important implications for the future, as the supramolecular approach to medicinal-chemistry products outlined here is rapidly allowing nanotechnology to converge with medicine. In particular, this article discusses recent developments including the rational design of drugs s...