Resumen: Se presenta la valoración que 5 profesores y 218 estudiantes de 3º ESO hacen de las analogías incluidas en una propuesta de enseñanza para el estudio de los estados de agregación. Con las analogías como recurso didáctico se pretendía que los alumnos comprendieran el modelo cinético molecular de la materia necesario para justificar las propiedades de sólidos, líquidos y gases, y su comportamiento durante los cambios de estado. Se utilizaron diferentes analogías (batallón militar, pista de baile, partido de fútbol y clase de educación física), con una estrategia didáctica que evoluciona desde la presentación de la analogía por el profesor a la construcción de la analogía por los estudiantes. Para valorar las analogías se ha diferenciado el grado en que se comprenden y se consideran adecuadas, viables e interesantes para la enseñanza de las ciencias. Tanto profesores como alumnos han valorado positivamente las analogías empleadas; los primeros comparten su intencionalidad y dificultad didáctica, y los segundos consideran que las analogías son una herramienta útil que les ayuda no solo a comprender el modelo cinético molecular sino a explicar las propiedades y cambios de los estados de agregación de la materia, es decir, el fenómeno en sí mismo. Palabras clave: analogías; percepciones; propuesta de enseñanza; estados de agregación de la materia; educación secundaria obligatoria. Perception of teachers and students at 3th year of Secondary School about they use analogies to understand the states of the matter Abtsract: In this study we show the perception of 5 teachers and 218 students at 3th year of Secondary School about the analogies included in an educational unit to understand the states of matter. We expected our students understood the molecular kinetic model of matter with analogies, since it is necessary to explain the properties of the solid, liquid and gaseous state of matter and to prove their performance during the change of state. Different types of analogies were used: a battalion, a dance floor, a football match and a PE class, with an evolving didactic strategy starting with the presentations of analogies by the teacher and ending by the fulfilment of analogies by the students. To evaluate these analogies it has been distinguished the degree by which they are understood, suitable, viable and interesting for the study of Science. The analogies used have been considered positive by both, teachers and students. Teachers share their wilfulness and didactic difficulty and students think analogies are useful tools which help them to understand the molecular kinetic model to explain the properties and the changes of the states of matter, that is to say, to understand the phenomenon itself.

The selection and sequencing of syllabus content is one of the main tasks the teacher has to approach in his/her new role as curriculum designer. The teaching proposals produced should be theoretically-driven so that specific procedures are suggested for the analysis of disciplinary content and pupils’ characteristics. Knowledge regarding teachers’ beliefs about these proposals, the difficulties involved in learning them and their scope of application is necessary in order to analyze how adequate they might be for inducing educational changes. In this paper, we present the initial teaching beliefs and teaching practices of a group of secondary school teachers who had previously received a training course in which a teaching proposal was presented. Also, some information is outlined concerning their assessment of the proposal as well as the learning and educational changes effected.

La formación inicial del profesorado de Educación Secundaria ha introducido cambios importantes en el currículum formativo de los futuros docentes. Creemos que es necesario reflexionar y analizar lo que estamos haciendo para mejorarlo. Este trabajo se centra en una de las materias novedosas del plan de estudios: el Trabajo Fin de Master (TFM).

This study puts forward some planning strategies for the teaching of Science based on a constructivist approach for the teachingflearning process. These strategies are shown in a model for the design of teaching units which includes five interdependent tasks: scientific analysis, pedagogical analysis, selection of objectives, selection of pedagogical strategies and selection of evaluation strategies. The first two aim at the reflection and estimation of contents and constrains of the teachingllearning processes. The other three are concerned with teachers' decision making and the explicitness of their teaching plans, as well as with their classroom performance in order to achieve them.La preparación de una lección es una tarea que ha de acometer el docente. ¿Qué contenidos incluyo en la lección? ¿Por dónde comienzo su desarrollo? ¿Qué experiencias de laboratorio debo hacer? ... son algunas de

Resumen. El trabajo estudia cómo perciben unos profesores principiantes la viabilidad de las propuestas didácticas que se plantean en un curso de formación inicial del profesorado de educación secundaria de física y química cuando se encuentran ante aulas y centros reales. Además se profundiza en las causas de la escasa viabilidad de algunos conocimientos, que se agrupan en cuatro ámbitos: conocimientos y creencias, demandas de formación, características de los alumnos y factores contextuales. Finalmente se establecen algunas implicaciones para la formación del profesorado.Palabras clave. Formación inicial, profesores principiantes, educación secundaria, física y química, viabilidad. The viability of didactic proposals in initial teacher training: Opinions, diffi culties and needs of beginning teachersSummary. This study explores how fi ve secondary beginning teachers perceive the viability of didactic proposals that had been worked during one course of initial Physics and Chemistry teacher training, when they fi nd themselves in the presence of real classrooms in real schools. Besides we analyse the reasons for the scarce viability of some proposals, grouped in four fi elds: knowledge and beliefs, demands of training, students characteristics and contextual factors. Finally we establish some implications for teacher training.