Investigating the effectiveness of a POE-based teaching activity on students’ understanding of condensation

Cataloged from PDF version of article.This article reports on the development of a Predict–Observe–Explain, POEbased teaching strategy to facilitate conceptual change and its effectiveness on student understanding of condensation. The sample consisted of 52 first-year students in primary science education department. Students’ ideas were elicited using a test consisting of five probe questions and semi-structured interviews. A teaching activity composed of three Predict–Discuss–Explain–Observe–Discuss–Explain (PDEODE) tasks was employed, based on students’ preconceptions identified with the test. Conceptual change in students’ understanding of condensation was evaluated via a pre-, post-, and delayed post-test approach and students’ interviews. Test scores were analyzed using both qualitative and quantitative methods. The findings suggested that the strategy helps students to achieve better conceptual understanding for the concept of condensation and enables students to retain these new conceptions in their long-term memory

Assessing prospective chemistry teachers' understanding of gases through qualitative and quantitative analyses of their concept maps

Cataloged from PDF version of article.The use of concept mapping as a tool to measure the meaningful learning of students is the focus of this study. The study was carried out with 24 last year students (22 years old) from the Department of Chemistry Teaching at Fatih Faculty of Education, Karadeniz Technical University (KTU). Prospective Chemistry Teachers (PCT) were asked to create concept maps using a list of given concepts related to gases. An examination of the PCTs' maps revealed that the students could not form hierarchical maps even after being shown examples of the basic elements and meaningful propositions between the concepts. After being provided with feedback about their concept maps and trained to form non-hierarchical concept maps, the students were asked to create new maps. This time they were allowed to use either hierarchical or non-hierarchical maps. When their new maps were examined, we found that most of the PCTs formed non-hierarchical maps. However, they still could not form meaningful relationships between the given concepts. We also found that the PCTs had some misconceptions about gases and kinetic molecular theory that explains gas behavior. The study ended up with some suggestions and implications for educators and researchers related to pre-service teachers' training

The Effectiveness of Predict-Observe-Explain Technique in Probing Students' Understanding about Acid-Base Chemistry: A Case for the Concepts of pH, pOH and Strength

Cataloged from PDF version of article.The present study describes high school students’ conceptions about acids and bases in terms of pH, pOH, microscopic level, strength, and concentration. A total of 27 high school students participated in the study. The data was collected using 3 POE tasks and a semi-structured interview. The data analysis demonstrated that most of the students had poor understanding related to a drawing of weak and strong acids. In addition, the findings revealed that the POE’s were effective in terms of gathering students’ predictions and reasons for the prediction of outcomes in an open-ended format. The POE tasks also revealed that some of the students had misconceptions regarding pH and pOH. The students believed that pH was a measurement of the acidity, while pOH was a measurement of the basicity. The findings obtained have certain implications for the secondary chemistry program

Counting molecules with a mobile phone camera using plasmonic enhancement

Cataloged from PDF version of article.Plasmonic field enhancement enables the acquisition of Raman spectra at a single molecule level. Here we investigate the detection of surface enhanced Raman signal using the unmodified image sensor of a smart phone, integrated onto a confocal Raman system. The sensitivity of a contemporary smart phone camera is compared to a photomultiplier and a cooled charge-coupled device. The camera displays a remarkably high sensitivity, enabling the observation of the weak unenhanced Raman scattering signal from a silicon surface, as well as from liquids, such as ethanol. Using high performance wide area plasmonic substrates that enhance the Raman signal 10(6) to 10(7) times, blink events typically associated with single molecule motion, are observed on the smart phone camera. Raman spectra can also be collected on the smart phone by converting the camera into a low resolution spectrometer with the inclusion of a collimator and a dispersive optical element in front of the camera. In this way, spectral content of the blink events can be observed on the plasmonic substrate, in real time, at 30 frames per second

Improving students' understanding and explaining real life problems on concepts of reaction rate by using a four step constructivist approach

The aim of this study was to investigate the effects of activities developed based on a four-step constructivist approach on students' understanding and explaining real-life problems about reaction rate concepts in chemistry. The study was carried out with 41 eleventh grade students, from two different classes attending a secondary school in Turkey. Two classes were randomly designated as experimental and control groups. While teaching the subject, a four-step constructivist approach was used for the experimental group whereas in control group, students were taught by the traditional method. Teaching activities in both groups were observed by one of the researchers. In both groups, Real-life Relating Test (RRT), including the phenomena that students observe in their daily life about reaction rate concepts was implemented before and after the intervention. Also semi-structured interviews were conducted with 13 students chosen from the both groups. At the end of the study, it was determined that the intervention which was carried out based on a four-step constructivist approach helped more the students in explaining real-life problems in a scientific way and provide more lasting learning than traditional approach. It is suggested that such activities should be used in other abstract or problematic concepts in chemistry. © Sila Science. All rights reserved

Virtual chemistry laboratory: Effect of constructivist learning environment

The lab applications, which were started to be applied through mid 19th century, not only provide a new point of view but also bring about a new dimension to the lessons. At early times they were used to prove theoretical knowledge but lately they turned into environments where students freely discover knowledge as an individual or in groups. The activities that have come up with the recent form of labs substantially contributed to training ideal students for constructivist approach, who research, inquire, test, seek solutions, wear scientist shoes and deeply reason about the concept of concern. However, on the present stage of our educational system, these activities cannot be included in science lessons for several reasons. At that point virtual labs emerged as an alternative solution for the problems of the instruction in science courses. Thanks to virtual labs presenting different disciplines in a flexible manner, the interaction between the teacher and the learner become 7/24 independent from time and place. This article presents a study that provides insight in the appropriateness of Virtual and real laboratory applications on constructivist learning environment using interactive virtual chemistry laboratory (VCL) development was used in academic year of 2009-2010 for a six week period. The sample of this quasi-experimental study was 90 students from three different 9th grade classrooms of an Anatolian Secondary school in the center of Trabzon city. The student groups were randomly attained as one experimental and two control groups. The data collection tools of the study were; questionnaire of teaching philosophy (QTP), Semi-structured interviews and unstructured observations. The results showed that virtual chemistry laboratory software was just as effective as real chemistry laboratory and it positively affected the facilitating of constructivist learning environment. It was determined that the students in experimental group conducted the experiments as precise as the real ones; they felt themselves safe during the experiments; they could relate the experiments with daily life; they had the opportunity to investigate both macro-molecular and symbolical dimensions of the experiments. It was speculated that using virtual chemistry laboratories as a supportive complement in education will become an indispensable instructional material in terms of both the economy of the nation and the persistency of the learning

Probing hot-electron effects in wide area plasmonic surfaces using X-ray photoelectron spectroscopy

Plasmon enhanced hot carrier formation in metallic nanostructures increasingly attracts attention due to potential applications in photodetection, photocatalysis, and solar energy conversion. Here, hot-electron effects in nanoscale metal-insulator-metal (MIM) structures are investigated using a non-contact X-ray photoelectron spectroscopy based technique using continuous wave X-ray and laser excitations. The effects are observed through shifts of the binding energy of the top metal layer upon excitation with lasers of 445, 532, and 650 nm wavelength. The shifts are polarization dependent for plasmonic MIM grating structures fabricated by electron beam lithography. Wide area plasmonic MIM surfaces fabricated using a lithography free route by the dewetting of evaporated Ag on HfO2 exhibit polarization independent optical absorption and surface photovoltage. Using a simple model and making several assumptions about the magnitude of the photoemission current, the responsivity and external quantum efficiency of wide area plasmonic MIM surfaces are estimated as 500 nA/W and 11 × 10-6 for 445 nm illumination. © 2014 AIP Publishing LLC

Raman Enhancement on a Broadband Meta-Surface

Cataloged from PDF version of article.Plasmonic metamaterials allow confinement of light to deep subwavelength dimensions, while allowing for the tailoring of dispersion and electromagnetic mode density to enhance specific photonic properties. Optical resonances of plasmonic molecules have been extensively investigated; however, benefits of strong coupling of dimers have been overlooked. Here, we construct a plasmonic meta-surface through coupling of diatomic plasmonic molecules which contain a heavy and light meta-atom. Presence and coupling of two distinct types of localized modes in the plasmonic molecule allow formation and engineering of a rich band structure in a seemingly simple and common geometry, resulting in a broadband and quasi-omni-directional meta-surface. Surface-enhanced Raman scattering benefits from the simultaneous presence of plasmonic resonances at the excitation and scattering frequencies, and by proper design of the band structure to satisfy this condition, highly repeatable and spatially uniform Raman enhancement is demonstrated. On the basis of calculations of the field enhancement distribution within a unit cell, spatial uniformity of the enhancement at the nanoscale is discussed. Raman scattering constitutes an example of nonlinear optical processes, where the wavelength conversion during scattering may be viewed as a photonic transition between the bands of the meta-material

Microwave sintering of SiAlON ceramics with TiN addition

α-β SiAlON/TiN composites with nominal composition of α:= β25:75 were fabricated by microwave sintering. The effect of titanium nitride addition on the phases, microstructure, microwave absorption ability and mechanical properties (Vickers hardness and fracture toughness) of the SiAlON-based composites were studied. Finite Difference Time Domain (FDTD) software was used for the numerical simulation in order to assess the most suitable experimental setup. Sintering trials were performed in a single mode microwave furnace operating at 2.45 GHz and a power output of 660W, for a reaction time of 30 min. SiC blocks were used as a susceptor to accelerate the microwave processing by hybrid heating, with reduced heat losses from the surface of the material of the α- βSiAlON/TiN composites. The optimum comprehensive mechanical properties, corresponding to a relative density of 96%, Vickers hardness of 12.98 ± 1.81 GPa and Vickers indentation fracture toughness of 5.52 ± 0.71 MPa.m1/2 were obtained at 850°C when the content of TiN was 5 wt.%

Rounding corners of nano-square patches for multispectral plasmonic metamaterial absorbers

Multispectral metamaterial absorbers based on metal-insulatormetal nano-square patch resonators are studied here. For a geometry consisting of perfectly nano-square patches and vertical sidewalls, double resonances in the visible regime are observed due to simultaneous excitation of electric and magnetic plasmon modes. Although slightly modifying the sizes of the square patches makes the resonance wavelengths simply shift, rounding corners of the square patches results in emergence of a third resonance due to excitation of the circular cavity modes. Sidewall angle of the patches are also observed to affect the absorption spectra significantly. Peak absorption values for the triple resonance structures are strongly affected as the sidewall angle varies from 90 to 50 degrees. Rounded corners and slanted sidewalls are typical imperfections for lithographically fabricated metamaterial structures. The presented results suggest that imperfections caused during fabrication of the top nanostructures must be taken into account when designing metamaterial absorbers. Furthermore, it is shown that these fabrication imperfections can be exploited for improving resonance properties and bandwidths of metamaterials for various potential applications such as solar energy harvesting, thermal emitters, surface enhanced spectroscopies and photodetection. © 2015 Optical Society of America