Doctoral thesis (PhD in Education)This study aimed at developing curriculum materials that could address pupils’ learning difficulties. The study explored the characteristics and effectiveness of these materials in relation to children’s learning about Matter and its Change of state. It was conducted in two primary schools, namely Kaloleni and Mnadani, both located in Dodoma municipality, Dodoma region, Tanzania. Six Science teachers, i.e. three from each school, were involved in the study. Moreover, 263 Standard Six pupils – 93 from Kaloleni, and 169 from Mnadani, were involved in this study. Developmental and phenomenographical research designs were employed to generate data through focus group discussions (with teachers), syllabus review, interviews (with teachers), pre- and post-tests to pupils, and participant lesson observations. The study employed Variation Theory and Conceptual Change Model to explore the critical properties for defining matter and its states, and the transformation of these properties when physical and chemical changes of matter occur. Thus, the teaching involved conceptual change through creating variations to expose critical features of the learning objects. The pupils were made to confront their learning difficulties and misconceptions through practical tasks, demonstrations, concept maps, discussions, thought-provoking examples and probing questions. The use of locally available materials was an essential part of the learning experiences provided. The pre- and post-tests were analysed through frequencies, percentages, one-way between-groups ANOVA and one-way repeated measures ANOVA. Qualitative data were subjected to thematic analysis. The findings showed that, the pupils experienced more difficulty in identifying the properties of gases, than the properties of solids. It was easier for them to identify the properties of liquids, perhaps because they can be observed more clearly than those of invisible gas and non-moving solid. The most difficult aspect was that of explaining the properties of the three states of matter basing on its particulate nature. Furthermore, the pupils faced difficulty in distinguishing, bringing about and explaining the physical and chemical changes of matter. However, after interventions, the ANOVA showed an increase in the mean scores from pre-test to the post-test, with a very large effect size in all the subsequent cycles, indicating that the materials had been effective in reinforcing learning science about matter. It also showed a significant increase in post-test scores between groups in the successive cycles, with small to moderate effect size. The study sheds light on how to identify learning difficulties, structure and deliver science contents in relation to the pupils‟ learning needs, using conceptual change through creating variations. Therefore, this study served to improve Pedagogical-Content-Knowledge about matter and its states. Generally, the curriculum materials developed helped to confront pupils‟ content related learning difficulties. Hence, they can be adapted by other teachers teaching basic science with similar content areas. Therefore, Learning Study and Conceptual Change model can be used to address pupils‟ science content related learning difficulties, and develop materials for primary schools.