Challenging Misconceptions in the Chemistry Classroom: Resources to Support Teachers

El fet d'explicar i aprendre química pot ser considerat un repte i és freqüent que els estudiants desenvolupin concepcions alternatives de la química que se'ls ensenya. Aquest article relata un projecte de la Royal Society of Chemistry del Regne Unit que pretén ser una ajuda per al professorat. El projecte ha desenvolupat materials d'aula per identificar i encarar aquests conceptes erronis o concepcions alternatives. Aquests materials es van publicar l'any 2002 i ara s'estan donant a conèixer a través de la Societat Catalana de Química. El projecte es basa en una visió constructivista de l'aprenentatge i pretén no només posar de manifest les concepcions alternatives en l'aprenentatge de la química, sinó també donar resposta al com i al perquè es produeix aquest aprenentatge erroni. El professorat que conegui les concepcions alternatives més freqüents i que alhora sigui capaç d'anticipar on i quan els aprenentatges dels seus alumnes no es corresponen amb el que pretén ensenyar, estarà ben preparat per evitar o modificar algunes d'aquestes concepcions alternatives de la química.Teaching and learning chemistry can be challenging, and may often be complicated by students developing misconceptions of the chemistry they are taught. This article reports a pro - ject to support teachers, undertaken for the Royal Society of Chemistry in the UK. The project developed classroom materials to support teachers in identifying and challenging misconceptions. These materials were published in the UK in 2002, and are now being made available in translation by the Societat Catalana de Química. The project was informed from a constructivist stance where the aim is not just to recognise when students misunderstand the chemistry, but also to appreciate how and why such learning errors occur. A teacher who is both familiar with common misconceptions, and who is able to anticipate where and when learning is likely to distort teaching, is well equipped to avoid some of the common learning difficulties in the subject

Conceptual confusion in the chemistry curriculum: exemplifying the problematic nature of representing chemical concepts as target knowledge

Abstract: This paper considers the nature of a curriculum as presented in formal curriculum documents, and the inherent difficulties of representing formal disciplinary knowledge in a prescription for teaching and learning. The general points are illustrated by examining aspects of a specific example, taken from the chemistry subject content included in the science programmes of study that are part of the National Curriculum in England (an official document published by the UK government). In particular, it is suggested that some statements in the official curriculum document are problematic if we expect a curriculum to represent canonical disciplinary knowledge in an unambiguous and authentic manner. The paper examines the example of the requirement for English school children to be taught that chemical reactions take place in only three different ways (i.e., proton transfer; electron transfer; electron sharing) and considers how this might be interpreted in terms of canonical chemistry and within the wider context of other curriculum statements, in order to make sense of neutralisation and precipitation reactions. It is argued that although target knowledge that is set out as the focus of teaching and learning cannot be identical to disciplinary knowledge, the English National Curriculum offers a representation of chemistry which distorts and confuses canonical ideas. It is suggested that the process of representing the disciplinary knowledge of chemistry as curriculum specifications is worthy of more scholarly attention

Distributed pre-computation for a cryptanalytic time-memory trade-off

Cryptanalytic tables often play a critical role in decryption efforts for ciphers where the key is not known. Using a cryptanalytic table allows a time-memory tradeoff attack in which disk space or physical memory is traded for a shorter decryption time. For any N key cryptosystem, potential keys are generated and stored in a lookup table, thus reducing the time it takes to perform cryptanalysis of future keys and the space required to store them. The success rate of these lookup tables varies with the size of the key space, but can be calculated based on the number of keys and the length of the chains used within the table. The up-front cost of generating the tables is typically ignored when calculating cryptanalysis time, as the work is assumed to have already been performed. As computers move from 32 bit to 64 bit architectures and as key lengths increase, the time it takes to pre-compute these tables rises exponentially. In some cases, the pre-computation time can no longer be ignored because it becomes infeasible to pre-compute the tables due to the sheer size of the key space. This thesis focuses on parallel techniques for generating pre-computed cryptanalytic tables in a heterogeneous environment and presents a working parallel application that makes use of the Message Passing Interface (MPI). The parallel implementation is designed to divide the workload for pre-computing a single table across multiple heterogeneous nodes with minimal overhead incurred from message passing. The result is an increase in pre-computational speed that is close to that which can be achieved by adding the computational ability of all processors together

Biosphere 2 test module experimentation program

The Biosphere 2 Test Module is a facility which has the capability to do either short or long term closures: five month closures with plants were conducted. Also conducted were investigations of specific problems, such as trace gas purification by bioregenerative systems by in-putting a fixed concentration of a gas and observing its uptake over time. In other Test Module experiments, the concentration of one gas was changed to observe what effects this has on other gases present or on the system. The science of biospherics which encompasses the study of closed biological systems provides an opening into the future in space as well as in the Earth's biosphere

Evaluation of digital correction techniques for ERTS images

There are no author-identified significant results in this report

Secondary students' values and perceptions of science-related careers: responses to vignette-based scenarios.

There has been concern about the attractiveness of science-based careers to many adolescent learners, and it has been suggested that school science may not always recognise or engage personal values that are important to young people in making life choices. The present study discusses interview comments made by upper secondary level students in England when 15 young people were asked to give their personal responses to brief vignettes describing scientific careers. Using an interview-about-scenarios approach, the students were asked about whether they would feel comfortable working in the scientific careers represented. The career areas were purposefully selected because they might be considered to potentially raise issues in relation to personal values or commitments that some students might hold. A range of student perceptions relating to the mooted careers were elicited (positive, negative and indifferent), but all of the participants raised issues that impacted on the acceptability or attractiveness of at least one of the mooted scientific careers, in terms of aspects of their own personal beliefs and values systems. It is recommended that teachers and career advisors should be aware of the range of value-related considerations that influence student views of science-related careers and should consider exploring aspects of science-based careers that link to values commonly shared by young people. This exploratory study also offers indications for directions for further research exploring how learners' value systems impact upon their perceptions of science and scientific work.We acknowledge the support of the John Templeton Foundation under grant number: 15389

Dimensional Control and Formability in Impact Forming

Electromagnetic forming (EMF) is a high speed forming technique that can be used for embossing fine surface features onto sheet metals. Here two coupled experimental and analytical studies show how interface conditions including rebound and friction affect the ability to create a component in impact forming. In the first part of this work high velocity is generated with the Uniform Pressure Actuator (UPA) and impact with a die emboss fine features in a nominally flat component. The primary objective of this work is to develop a modelling facility that guides experimental design nominally flat grooved components. Both shape fidelity and formability aspects are presently considered. In a second short study expansion of a round tube into a square hole is considered. Traditional modelling techniques solve a coupled system of equations with spatially varying electromagnetic fluxes controlling the dynamics of the plastic deformation. Because the magnetic pressure is spatially uniform, the flux equations are obviated from the coupled system rendering them computationally efficient. The calibration of contact mechanics that influence the rebound behaviour of the sheet metal remains as a difficult issue. The interfaces between various sheet metals and the metal die play a critical role in controlling the shape of the final product. The characterization of such an interface using appropriate calibrated friction coefficients is assessed. The role of magnetic pressure in reducing the sheet metal rebound is demonstrated via a comparison between results from mechanical and electromagnetic simulations. The influence of the channel geometry on final shape is illustrated through simulation and experiments