Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This research aims at diagnosing alternative conceptions to scientific knowledge of students in Elementary Education, Middle and Upper on acids and bases. The survey was conducted between 2008 and 2009 and applied to 26 primary school students (ninth year), 36 high school (third year) and 51 Degree in Chemistry (26 freshmen and 25 trainees) totaling 113 students. The instrument used for data collection was mainly made up of open questions where the students described their concepts of acids and bases. The overall results of this study showed that students, after receiving formal instruction on acids and bases continue to use simplistic views on the subject many times in this work, we found misconceptions even among senior college students in the Degree Course in Chemistry. We realize that in general, the Arrhenius model prevails among the students, however, can not be said if students really understand acids and bases as particles or if they perceive these substances as mere words. Confusion between the various theories acid base were very common here, which leads us to believe that the teaching content too complex for the primary and secondary education become conflicting for the student, which does not contribute to an appropriation of such knowledge. In short, we can infer that this inventory of alternative conceptions expressed by students for the contents acids and bases is necessary because the importance of these concepts disclosed and discussed primarily with science teachers. Therefore, we expect to support a significant learning effectively through reflection on students' previous conceptions, which are an important tool for the proposition didactic classroom, since the strong resistance to a conceptual change that students present. / Esta investigação tem como objetivo diagnosticar as concepções alternativas ao conhecimento científico de estudantes de Ensino Fundamental, Médio e Superior sobre ácidos e bases. A pesquisa foi realizada entre 2008 e 2009 e aplicada a 26 alunos de ensino fundamental (nono ano), 36 de ensino médio (terceiro ano) e 51 de Química Licenciatura (26 calouros e 25 formandos) totalizando 113 estudantes. O instrumento utilizado para a obtenção de dados foi essencialmente constituído por questões abertas onde os alunos descreveram seus conceitos sobre ácidos e bases. Os resultados gerais desse estudo mostraram que os estudantes, mesmo depois de receber o ensino formal sobre ácidos e bases continuam a usar concepções simplistas sobre o tema, muitas vezes, neste trabalho, verificamos concepções errôneas mesmo entre os estudantes formandos no curso de Química Licenciatura. Percebemos que em geral, o modelo de Arrhenius predomina entre os estudantes, porém, não se pode afirmar se os estudantes realmente entendem os ácidos e as bases como partículas ou se percebem tais substâncias como meras palavras. Confusões entre as várias teorias ácido base foram muito comuns aqui, o que nos leva a acreditar que o ensino de conteúdos muito complexos durante os ensinos fundamental e médio tornam-se conflitantes para o aluno, o que não contribui para uma apropriação de tais saberes. Em suma, pode-se inferir que este inventário das concepções alternativas manifestadas pelos estudantes para o conteúdo ácidos e bases se faz necessário visto a importância de que estas concepções sejam divulgadas e principalmente discutidas com os professores de ciências. Sendo assim, esperamos corroborar para uma aprendizagem efetivamente significativa, através da reflexão sobre as concepções prévias dos alunos, as quais são uma importante ferramenta para a proposição didática em sala de aula, visto a forte resistência a uma mudança conceitual que os estudantes apresentam.

The purpose of this study was to investigate the effect of 5E learning cycle model compared to traditional teacher-centered instruction on eleventh grade students&rsquo / conceptual understanding of acids and bases concepts and student motivation to learn chemistry. The measuring tools were Three-tier Acids-Bases Test (TABT) and Chemistry Motivation Questionnaire (CMQ). There were two groups, which were the experimental and traditional group, consisting of 78 students. Before the implementation, the tools were administered as pre-tests to both groups and the semi-structured pre-interviews were conducted with eight students to determine students&rsquo / prior knowledge about acids-bases and motivation to learn chemistry. During the implementation, 5E learning cycle model was used in the experimental group and the traditional teacher-centered instruction was used in the traditional group throughout eight weeks. After the implementation, the tools were administered as post-tests to both groups and the semi-structured post-interviews were conducted with the same students to determine their post knowledge about acids-bases and motivation to learn chemistry. Afterwards, the data were analyzed and descriptive and inferential statistics were obtained. Based on MANCOVA results, there was a statistical significant mean difference between the groups in favor of experimental group. Similarly, the students from experimental group scored higher motivation and this difference was found to be statistically significant. The results were analyzed in terms of gender as well, and there was found no statistically significant differences between the post-test mean scores of girls and boys for the effect of the implementation on understanding of acids-bases concepts or motivation to learn. The inferential statistics results were also supported with the students interviews.

This study was conducted to compare the effectiveness of conceptual change text oriented instruction accompanied with analogies over traditional instruction on tenth grade students&rsquo / understanding of the acid and base concepts and attitude toward science as a school subject. In addition, effect of the gender difference and science process skills on students&rsquo / understanding of acid and base concepts and effect of gender difference on students&rsquo / attitudes toward chemistry as a school subject were also investigated. Subjects of the study were fifty tenth grade students from the two chemistry classes of the same teacher from a public school at the center of Ankara. There were one experimental group and one control group. Two teaching methods used were randomly assigned to the already formed groups of the teacher. Experimental group received conceptual change oriented instruction by using conceptual change text accompanied with analogies and control group received traditional instruction over a period of four weeks. Acid and Base Conception Test and Attitude Scale Toward Chemistry were given to all groups as a pre-test and post-test. Science Process Skill Test was given to all groups at the beginning of the study to determine students&#039 / level of science process skills. At the end of the study, interviews were hold with randomly selected experimental and control group students from the medium achievement level to get an in-dept idea about the nature of the misconceptions related with the topic. ANOVA and ANCOVA were used to test the hypotheses of the study. The results showed that establishing an analogical thinking during the course of instruction together with a conceptual change text caused a better acquisition of scientific conceptions and elimination of misconceptions related with acid and base concepts as compared to the traditional instruction. Because, the students in the experimental group taking conceptual change oriented instruction performed much better in the post-test than the students in the control group taking the traditional instruction. However, the two modes of the instruction and gender difference did not indicate a significant contribution to students&rsquo / attitude toward chemistry as a school subject. Besides, results showed that science process skills of the students&#039 / could be a strong predictor for their achievement in acid and base concepts whereas there was no significant effect of gender difference on students&rsquo / understanding of acid and base concepts.

Dans la problématique de l'utilisation de nouvelles énergies non polluantes, l'hydrogène est l'un des principaux carburants verts du futur. Les dérivés d'hydrazine et de borane sont potentiellement intéressants pour le stockage chimique de l'hydrogène. Les complexes entre hydrazines ou nitriles avec des boranes ou des alanes sont à la base de cette étude. Ces composés ont été synthétisés afin d'étudier leur structure électronique avant et après la création de la liaison entre les acides et les bases de Lewis. La spectroscopie photoélectronique à rayonnement UV (UV-SPE) est utilisée comme outil principal de caractérisation fournissant des énergies d'ionisation (IE). L’interprétation des résultats expérimentaux est supportée par des calculs quantiques comme ΔSCF + TD-DFT, OVGF, P3 et SAC-CI. Des simulations et des expériences par Flash Vacuum Thermolysis (FVT) ont été effectuées, portant sur l’élimination d'hydrogène à partir de dérivés d'hydrazine borane. / Within the problematic of the use of new non-polluting energies, hydrogen is one of the main green fuels of the future. Hydrazine borane derivatives are potentially interesting chemical hydrogen storage materials. Complexes between hydrazines or nitriles with boranes or alanes are the basis of this study. These compounds were synthesized in order to study their electronic structure before and after creation of the bond between the Lewis acids and bases. Ultraviolet Photoelectron Spectroscopy (UV-PES) is used as a main characterization tool, providing Ionization Energies (IE). The interpretation of the experimental results is supported by Quantum Chemical Calculations as ΔSCF+TD-DFT, OVGF, P3 and SAC-CI methods. Simulations and experiments by Flash Vacuum Thermolysis (FVT) were carried out on hydrogen release from hydrazine borane derivatives.

In this thesis, we investigate biological molecules on a micron scale in the ultraviolet spectral region through the non-destructive confocal absorption microscopy. The setup involves a combination of confocal microscope with a UV light excitation beam to measure the optical absorption spectra with spatial resolution of 1.4 μm in the lateral and 3.6 μm in the axial direction. Confocal absorption microscopy has the benefits of requiring no labels and only low light intensity for excitation while providing a strong signal from the contrast generated by the attenuation of propagating light due to absorption. This enables spatially resolved measurements of single live cells and bio-molecules with less than 10^9 molecules in the probe volume. Employing a multichannel detection system, the absorption spectrum of hemoglobin in a single red blood cell is measured on the timescale of seconds. We also extend the spectral range from the visible range to the experimentally more challenging ultra-violet region where characteristic absorption bands of bio-molecules are observed. Exploiting the ultra-violet range, amino acids, nucleic acids solutions, and plant cells are investigated. We measure the spatially resolved absorption spectra at the nucleus of an onion cell and cytoplasm to probe DNA base-pair absorption. Small variations in our micro-absorption data are seen around 260 nm, possibly due to the abundance of DNA in the nucleus. This thesis contributes to the goal of spectroscopic identification of spatial heterogeneities at the single cell level and the label-free detection of proteins and nucleic acids.