The development of proficiency in the practices used by scientists and engineers is considered an important student outcome of laboratory instruction. We developed tasks to assess students' use and development of selected scientific and engineering practices in the general chemistry laboratory using an adapted evidence-centered design approach. In this paper, we provide a detailed description of the process of development and validation of these assessment tasks, using one of our tasks to illustrate the process. The tasks show strong evidence of validity and reliability for revealing students' understanding of scientific and engineering practices within the research context.
Photoionization mass spectrometry reveals details of the multistep unimolecular mechanism, whereby the 2,2,6,6-tetramethyl-3,5-heptanedionato (thd−) anionic ligand decomposes, while still bound in the metal complex, to yield a gas-phase metal oxide product in metal−organic chemical vapor deposition (MOCVD) of lanthanide oxides from Ln(thd)3 precursors. The decomposition occurs with stepwise elimination of small closed-shell hydrocarbon fragments and carbon monoxide up to a penultimate Ln(OC2H) ethyneoxide, from which both LnO (dominant) and LnC2 (minor) products are derived. Formation of the metal oxide and carbide occurs in competition with a previously described mechanism
−
wherein sequential dissociation of ligand radicals produces the reduced metal Ln0. Evidence for gas-phase formation of a Ln2(thd)6 dimer as a result of expansion-cooling in the precursor source assembly is also given. Laser-assisted MOCVD of Eu(thd)3 on silica, with subsequent exposure to atmosphere, produces amorphous Eu2O3 with small areas of crystallinity attributed to reaction of the oxide with atmospheric carbon dioxide and water.
This 21-item survey administered at the end of first-semester General Chemistry asked students to estimate their average weekly use of course resources and rate how helpful they find various textbook and online homework features of their current textbook. During data collection, the General Chemistry textbook changed from a print version to one that is primarily electronic. A comparison of previous results of a print textbook semester to a semester using an ebook provided insight into how the equivalent features are utilized in different mediums. In the first three semesters' worth of data analyzed, General Chemistry I students report relying on their textbook for approximately 5 h of studying per week, regardless of textbook medium; when the ebook was adopted, the homework resource was more frequently used. A comparison of equivalent textbook features between formats revealed that the helpfulness ratings of reading outline and animations increased significantly, whereas worked-examples and end-of-chapter questions decreased significantly. In addition to mathemagenic features, ebook features that help students stay on-task or visualize reactions are significantly highly rated.
Dynamic biological processes, such as intracellular signaling pathways, commonly are taught in science courses using static representations of individual steps in the pathway. As a result, students often memorize these steps for examination purposes, but fail to appreciate either the cascade nature of the pathway. In this study, we compared eye movement patterns for students who correctly ordered the components of an important pathway responsible for vasoconstriction against those who did not. Similarly, we compared the patterns of students who learned the material using three dimensional (3-D) animations previously associated with improved student understanding of this pathway against those who learned the material using static images extracted from those animations. For two of the three ordering problems, students with higher scores had shorter total fixation duration when ordering the components and spent less time (fixating) in the planning and solving phases of the problem-solving process. This finding was supported by the scanpath patterns that demonstrated that students who correctly solved the problems used more efficient problem-solving strategies.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.