Neste trabalho utilizou-se o mapa conceitual como ferramenta para analisar a estrutura conceitual de alunos de um curso de graduação em química de uma universidade pública do estado de São Paulo, sobre o tema equilíbrio químico em dois momentos distintos, o primeiro ao ingressarem na universidade e o segundo após um ano de curso. Os mapas foram analisados utilizando uma adaptação do método de Análise Estrutural de Mapas Conceituais (AEMC adaptada). Teve-se como meta do trabalho: a) Avaliar, através de mapas conceituais elaborados pelos alunos a estrutura conceitual dos mesmos referente ao conceito equilíbrio químico; b) Descrever e analisar a evolução das relações entre os principais conceitos envolvidos no tema feitas por alunos no seu ingresso no curso de graduação e após um ano de curso, quando são submetidos pela primeira vez a um estudo sistemático do tema. Pretendeu-se assim, verificar quais foram às mudanças mais significativas ocorridas em decorrência das disciplinas ministradas neste período e c) Estabelecer uma relação entre estas mudança com o processo de ensino ao qual o aluno foi submetido, ou seja, como a estrutura conceitual dos estudantes a respeito do tema mudou em função do processo de aprendizado a que foram submetidos. Concluiu-se que a ferramenta desenvolvida durante a pesquisa foi muito útil na análise proposta; onde os alunos ingressantes definem o Equilíbrio químico como o estado onde as velocidades das reações se igualam sem relacionar a conceitos da termodinâmica, estes também, demonstraram muitos conhecimentos oriundos de como o conceito é apresentado no ensino médio. Verificou-se também que os estudantes ao serem submetidos à disciplinas relacionadas ao tópico equilíbrio químico modificaram seu entendimento sobre o tema. / In this work it was used the Concept Map as a tool for analyzing the conceptual structure of students in an undergraduate degree in Chemistry from a public university in the state of São Paulo, on the subject of Chemical Equilibrium at two different times, the first at the moment when entered in the university and second after a year. The maps were analyzed using an adaptation of the method of Structural Analysis of Concept Maps (AEMC adaptada). The objectives of work were: a) Explore and modify a method of analysis of Concept Maps in order to obtain a Concept Map that shows the main conceptual connection of a group of students in order to graphically represent their conceptual structure; b) Evaluate, through Concept Maps prepared by students their conceptual framework for the Chemical Equilibrium concept; c) Describe and analyze the evolution of relations between the main concepts involved on the subject made by students in their admission to the undergraduate course and after one year course, when they are first subjected to a systematic study of the subject. Thus the intention was to verify which were most significant changes occurred as a result of the matter taught in this period and d) Establish a connection between these changes with the teaching process to which the student was submitted, ie, how the conceptual framework of students regarding the subject changed as a function of the learning process they have submitted. It was concluded that the tool developed during the research was very useful in analyzing the proposal, which the new students define the Chemical Equilibrium as state where the velocities of reactions are equal without relating the concepts of thermodynamics, they also showed a lot of knowledge from as the concept is presented in high school. It was also found that students be subjected to the disciplines related to the topic Chemical Equilibrium changed their understanding of the subject, therefore, provide a greater number of connections between the different concepts involved on the matter.

In particle induced desorption-ionization mass spectrometry the strength of an analyte's signal under a given set of bombardment conditions is usually considered to be representative of the analytes relative surface activity. This rationale is generally used to explain differences in the technique's sensitivity between and within various classes of compound. In liquid matrix assisted secondary ion mass spectrometry (SIMS) sensitivity enhancement of ionic analytes by pairing with surface active counterions has been demonstrated by several groups. This technique has been utilized in this work to achieve a 10,000 fold enhancement in the signal for ATP on a double focusing magnetic sector instrument and to detect femtomole quantities of nucleoside monophosphates on a time-of-flight instrument. The analyte's signal, however, is dependent on both the analyte bulk concentration and that of the surfactant. Additionally, the surfactant concentration that produces the maximum analyte signal changes with the analyte concentration. In this study, this phenomenon has been modeled in terms of conventional solution equilibria and surface chemical principles. It is assumed that the initial surface composition and the bulk concentration are the boundary conditions of a steady state established by the competing processes of surface sputtering and surface replenishment from the bulk during analysis. Calculated surface excesses correlate well with observed relative ion intensities, suggesting that equilibrium conditions are approached in the sample matrices despite the outwardly dynamic nature of the sputtering processes. / Graduation date: 1994

The objectives of this work are to measure phase equilibria in the carbon dioxide + pyrrole system and to correlate and predict the phase behavior of this system with a thermodynamic model. This binary system is of interest due to the growing applications of supercritical carbon dioxide as a solvent or reaction medium for pyrrole. Polypyrrole is an electrically conducting polymer of interest in a number of applications such as anti-static coatings. Pyrrole has also been used as a reactant in enzymatic reaction. Knowledge of the phase behavior of carbon dioxide + pyrrole system is therefore necessary for evaluating optimal conditions and feasibility of such applications. Phase equilibria in the carbon dioxide + pyrrole system were measured at 313 K, 323 K, and 333 K using a synthetic method. Liquid-vapor (LV) phase behavior and liquid-liquid (LL) phase behavior were observed. The pressure in the experiments ranged from 84 to 151.1 bar. The Patel-Teja equation of state and the Mathias-Klotz-Prausnitz mixing rule with two temperature independent parameters was able to correlate the phase equilibrium data satisfactorily and was used to predict the phase behavior at other temperatures. A pressure-temperature diagram was then constructed from these calculations and suggests that the carbon dioxide + pyrrole system exhibit type IV phase behavior in the classification of Scott and van Konynenburg.

Vapour-Liquid Equilibrium (VLE), Liquid-Liquid Equilibrium (LLE) and Vapour-Liquid-Liquid Equilibrium (VLLE) are of special interest in chemical engineering as these types of data form the basis for the design and optimization of separation processes such as distillation and extraction, which involve phase contacting. Of recent, chemical companies/industries have required thermodynamic data (especially phase equilibrium data) for chemicals that are expensive or costly to synthesize. Phase equilibrium data for such chemicals are scarce in the open literature since most apparatus used for phase equilibrium measurements require large volumes (on average 120 cm3) of chemicals. Therefore, new techniques and equipment have to be developed to measure phase equilibrium for small volumes across reasonable temperature and pressure ranges. This study covers the design of a new apparatus that enables reliable vapour pressure and equilibria measurements for multiple liquid and vapour phases of small volumes (a maximum of 18 cm3). These phase equilibria measurements include: VLE, LLE and VLLE. The operating temperature of the apparatus ranges from 253 to 473 K and the operating pressure ranges from absolute vacuum to 1600 kPa. The sampling of the phases are accomplished using a single Rapid-OnLine-Sampler- Injector (ROLSITM) that is capable of withdrawing as little as 1μl of sample from each phase. This ensures that the equilibrium condition is not disturbed during the sampling and analysis process. As an added advantage, a short equilibrium time is generally associated with a small volume apparatus. This enables rapid measurement of multiple phase equilibria. A novel technique is used to achieve sampling for each phase. The technique made use of a metallic rod (similar in dimension to the capillary of the ROLSITM) in an arrangement to compensate for volume changes during sampling. As part of this study, vapour pressure and phase equilibrium data were measured to test the operation of the newly developed apparatus that include the following systems: • VLE for 2-methoxy-2-methylpropane + ethyl acetate at 373.17 K • LLE for methanol + heptane at 350 kPa • LLE for hexane + acetonitrile at 350 kPa • VLLE for hexane + acetonitrile at 348.20 K New experimental vapour pressure and VLE data were also measured for systems of interest to petrochemical companies. These measurements include: • VLE for methanol + butan-2-one at 383.25, 398.14 and 413.20 K ABSTRACT • VLE for ethanol + butan-2-one at 383.26, 398.23 and 413.21 K • VLE for ethanol + 2-methoxy-2-methylbutane at 398.25 and 413.19 K • VLE for ethanol + 2-methylpent-2-ene at 383.20 K These measurements were undertaken to understand the thermodynamic interactions of light alcohols and carbonyls as part of a number of distillation systems in synthetic fuel refining processes which are currently not well described. Two of these above mentioned systems include expensive chemicals: 2-methoxy-2-methylbutane and 2-methylpent-2-ene. The experimental vapour pressure data obtained were regressed using the extended Antoine and Wagner equations. The experimental VLE data measured were regressed with thermodynamic models using the direct and combined methods. For the direct method the Soave-Redlich-Kwong and Peng-Robinson equations of state were used with the temperature dependent function (α) of Mathias and Copeman (1983). For the combined method, the virial equation of state with the second virial coefficient correlation of Tsonopoulos (1974) was used together with one of the following liquid-phase activity coefficient model: TK-Wilson, NRTL and modified UNIQUAC. Thermodynamic consistency testing was also performed for all the VLE experimental data measured where almost all the systems measured showed good thermodynamic consistency for the point test of Van Ness et al. (1973) and direct test of Van Ness (1995). / Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2011.

Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2012.

No description available.

Thesis (Ph. D.)--University of California, San Diego, 1998. / Vita. Includes bibliographical references (p. 150-155).

Thesis (M.S.)--Mississippi State University. Department of Aerospace Engineering. / Title from title screen. Includes bibliographical references.

The purpose of the study was to collect and collate information pertaining to common misconceptions of components of the concept of chemical equilibrium amongst a sample of Transkeian matriculants. 'Equilibrium' is a fundamental concept in physics and chemistry and 'chemical equilibrium' is an important chemistry topic in both the higher grade and standard grade South African matriculation physical science syllabuses. In recent years, South African teachers have identified chemical equilibrium as the most difficult section of the matric physical science syllabus for both teachers and pupils. It has been shown that teachers themselves lack understanding of the basic concepts underlying chemical equilibrium. Constructivist learning theories arise out of research in cognitive psychology. These theories conceive of cognitive development as the assimilation and accommodation of new ideas into extant, dynamic cognitive structures. An inference from the theories is that a study of the preconceptions and/or misconceptions held by pupils before they are exposed to instruction would enable teachers to avoid generating or reinforcing misconceptions. Hence teachers could also take deliberate steps to eradicate those already existing. The sample consisted of 112 Transkeian matriculants from four government senior secondary schools in the Southern Transkei. All were taking physical science. The test consisted of a 40 item multiple choice battery. Each question had three distracters and the options were randomized to avoid patterns and hence guessing. Questions dealing with closely associated concepts were grouped in the paper but no indication of this was given in the paper. The questions are analyzed singly. A brief introduction and outline of the theory on which the group of questions was based is given in each case. The analysis makes use of the frequency of choice of all options, discrimination indices, although they were generally low and item difficulties. The intent in each analysis is to identify the possible misconception(s) underlying wrong answers. Finally conclusions based on the discussion are drawn and recommendations for teaching and further research made.

Submitted by ALEXANDER ALBERTO RODRIGUEZ GAMBOA null (alexander.r.gamboa@gmail.com) on 2016-05-06T06:12:01Z No. of bitstreams: 1 ALEXANDER ALBERTO RODRIGUEZ GAMBOA D Final.pdf: 2835466 bytes, checksum: 371027696e6cde2bf330e85c69c9370e (MD5) / Approved for entry into archive by Felipe Augusto Arakaki (arakaki@reitoria.unesp.br) on 2016-05-09T18:46:42Z (GMT) No. of bitstreams: 1 gamboa_aar_me_guara.pdf: 2835466 bytes, checksum: 371027696e6cde2bf330e85c69c9370e (MD5) / Made available in DSpace on 2016-05-09T18:46:42Z (GMT). No. of bitstreams: 1 gamboa_aar_me_guara.pdf: 2835466 bytes, checksum: 371027696e6cde2bf330e85c69c9370e (MD5) Previous issue date: 2016-03-07 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O presente trabalho foi desenvolvido com a finalidade de avaliar a combustão do óleo pirolítico, obtido a partir de pneus inservíveis, tendo sido levadas em consideração as viabilidades energética e ambiental para seu emprego como combustível alternativo, em um processo de combustão convencional. A primeira etapa consistiu em uma revisão da literatura sobre a grande quantidade de pneus inservíveis gerados no mundo e as principais rotas de disposição destes, a fim de ressaltar a relevância do estudo do óleo pirolítico de pneus (OPP) como uma alternativa de solução energética e ambiental. Assim como, verificaram-se suas principais propriedades físico-químicas, que fazem deste, um atrativo combustível alternativo. Posteriormente, foi desenvolvido um modelo de equilíbrio químico utilizando o método de minimização da energia livre de Gibbs para obter uma estimativa da formação e emissão dos principais produtos da combustão do OPP. Neste, foram avaliadas as concentrações dos produtos da combustão da mistura de óleo pirolítico de pneus e óleo diesel, focando-se principalmente na influência promovida pelas emissões de SO2 ao se aumentar a concentração do óleo diesel na mistura. Os testes experimentais foram realizados utilizando uma câmara de combustão de paredes não isoladas, constituída de dois módulos desmontáveis. Foi empregado nestes testes um queimador, no qual foi montado um swirler axial de pás movíveis que permitiu avaliar a influência do ângulo das pás do swirler sobre as concentrações dos produtos da combustão (CO, CO2, NOx e O2). Um problema crucial foi a elevada formação e deposição de material particulado, o que conduziu os experimentos a algumas paradas durante os testes, devido ao entupimento reiterativo do bico injetor e do filtro do compressor, utilizado na exaustão. Os resultados evidenciaram a viabilidade do uso do OPP como combustível alternativo, utilizando-se apenas um atomizador comercial tipo pressure swirl para sua atomização. A chama ficou estável para valores de razão de equivalência abaixo de 0,92. Além disso, as emissões de CO, CO2 e NOx foram comparáveis com aquelas obtidas por outros pesquisadores que queimaram óleo diesel. / This study was conducted in order to evaluate the combustion of pyrolytic oil derived from waste tires, for which the energy and environmental feasibility of its use as an alternative fuel in a conventional combustion process were considered. The first stage consisted in a review of literature about the large amount of waste tires generated in the world and the main disposal routes of them, to highlight the relevance of the study of tyre pyrolytic oil (TPO) as an alternative energy and environmental solution. Also, its main physico-chemical properties that make it an attractive alternative fuel was verified. After that, a chemical equilibrium model using the Gibbs free energy minimization method to obtain an estimate of the formation and emission from the main combustion products of TPO was developed. At this, the concentrations of the combustion products of the blend between tyre pyrolytic oil and diesel fuel were assessed mainly focused on the promoted influence by SO2 emissions with the increase of diesel fuel in the mixture. The experiments were carried out using a combustion chamber of non-isolated walls that consisted of two removable modules. A burner was used in the experiments, which was mounted an axial swirler of movable blades that allowed to assess the influence of the swirler blades angle on concentrations of combustion products (CO, CO2, NOx and O2). A crucial issue was the elevated formation and deposition of particulate matter, which led the experiments a few stops during the tests, due to reiterative clogging the nozzle and compressor filter used in the exhaust. The results showed the viability of the TPO's use as an alternative fuel, using only a commercial type atomizer pressure swirl for its atomization. The flame was stable for the equivalence ratio values below 0.92. Furthermore, emissions of CO, CO2 and NOx were comparable with those obtained by other researchers who burned diesel fuel.