The importance of the concepts of 'amount of substance' and 'mole' is supported by the abundance in the last decade of research papers on the problem of the teaching and learning of these concepts. The present study attempts a review of the relevant bibliography, including recent investigations on both the difficulties of learning these concepts and the didactic alternatives that are provided from different perspectives. The literature reviewed shows that students have great difficulty in handling the above concepts. In addition, a clear discrepancy exists between what is assumed as correct by the scientific community and the thinking of educators. Finally, strategies for the teaching of these concepts emerge.

In this study the origin and evolution of the meanings of the concepts 'amount of substance' and 'mole' are described. Serious disagreements about these concepts amongst chemistry teachers and the recommendations of the international scientific community are identified. Attention is also drawn to the didactic implications that these epistemological difficulties may have for the teaching of chemistry.

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In this work we describe the origin and evolution of the meaning of «amount of substance» and mole concepts considering the contributions made by the History of Chemistry. Moreover, we state the serious disagreement on these concepts between Chemistry teachers’ present thought and the recommendations of the international scientific community. We also draw attention to the didactic implications these epistemological difficulties may have for the teaching of Chemistry.

The main objective of this paper is the identification of the students' representations about the idea of substance quantity and to see to what extent the establised Chemistry teaching in Secondary schools contributes to giving them a more atomist view of matter. The results obtained in this work confirm that students, upon completing their studies, have practically not changed their 'globalist' conception of substance quantity, and only half of those that studied chemistry master the necessary activity to be able to understand the mole concept.

Resumen. Este trabajo trata del diseño y desarrollo de una investigación en el aula sobre la enseñanza de los conceptos de cantidad de sustancia y de mol. Se fundamenta en una concepción constructivista del proceso de enseñanza-aprendizaje de la ciencia como investigación orientada. En este proceso se han tenido en cuenta los componentes conceptual, metodológico y actitudinal del aprendizaje y se han analizado las difi cultades de los estudiantes al abordar el estudio del tema. Los resultados obtenidos ponen de manifi esto que, en un contexto de enseñanza-aprendizaje como investigación orientada, los estudiantes son capaces de utilizar con comprensión conceptos de alto nivel de difi cultad como los tratados.Palabras clave. Enseñanza-aprendizaje como investigación orientada, educación secundaria, diseño didáctico, cantidad de sustancia, mol. Teaching of the concepts «amount of substance» and mol based on a pattern of learning as oriented researchSummary. This study deals with the design and implementation of a research on the concepts of «amount of substance» and «mol». This work is grounded on a constructivistic conception of the learning of Sciences, more particularly on the model known as teaching-learning as oriented research. In accordance with this theoretical basis we have developed an empirical research framed within the teaching of Chemistry in High School. The developed designs have enabled us to assess the learning achieved by the students from a conceptual, procedural and attitudinal stance. According to our fi ndings we could say that the materials developed and the way we have worked with them have contributed to a more signifi cant learning and favoured a more positive attitude toward the teaching of the subject.

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