936The research reported in this paper investigates the impact of, and challenges with, encouraging argumentation on students' conceptual development in physics. It draws its theoretical framework from two socio-cultural perspectives of learning, i.e. that learning science occurs in a social setting and secondly that learning science is a discursive and cultural process. A three stage teaching sequence intended to encourage argumentation was implemented at a government high school in Maseru in 2009. Data were collected through audio taping of group discussions and students' written reports. The results show that the introduction of argumentation as a strategy of introducing learner -centred approaches in science classrooms proved to be benefi cial for concept development. The challenges of practicing argumentation include the use of second language and enculturation of students into a scientifi c community. Students carried out part of their discussions in Sesotho the fi rst language, instead of English the second language which is used as the medium of instruction. Students also used short sentences that needed elaboration and rarely questioned one another's justifi cations.

This qualitative study sought to investigate how secondary level chemistry teachers transform and represent subject matter knowledge (SMK). The study drew its theoretical framework from the notion of Pedagogical Content Knowledge (PCK) that foregrounds the teachers' ability to transform and represent SMK for students to understand the content presented. Seven qualified chemistry teachers participated in this study which used questionnaires, follow-up interviews, and lesson observations to collect data. The teachers were observed teaching the topic of stoichiometry to grade 11 students. Data analysis started with a coding system that resulted in themes of meanings suggested by teachers. The results show that chemistry teachers participating in the study were aware of different teaching strategies but their choice of those strategies was not informed by an attempt to transform the concepts. It is argued that teachers' failure to transform concepts will have a negative impact on students' understanding of these concepts.

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