Effect of Problem Based Learning on Achievement and Perceptions among Secondary School Students Learning Electrolysis in Rwanda

Abstract Electrolysis is among the most challenging topics in secondary school chemistry in Rwanda, characterized by persistent student misconceptions about electron transfer, redox reactions, and electrode processes, and by pedagogical approaches that prioritize rote memorization over conceptual understanding. This mixed-methods quasi-experimental study investigated the effect of Problem-Based Learning (PBL) on Senior Five students' academic achievement and perceptions in electrolysis in Kicukiro and Gasabo Districts, Rwanda. A convergent parallel mixed-methods design was employed. GS Remera Protestant School (Kicukiro District) served as the experimental group (n = 46), receiving eight weeks of PBL-based electrolysis instruction in which students collaboratively investigated real-world electrochemical problems. ES Bumbogo School (Gasabo District) served as the control group (n = 46), receiving conventional teacher-centred instruction on the same topics. Data were collected through a researcher-developed Electrolysis Achievement Test (EAT) administered at pre-test and post-test stages, a Students' Perceptions of Problem-Based Learning Questionnaire (SPBLQ), and semi-structured teacher interviews. Test-retest reliability was confirmed (r = 0.89). Data were analysed using independent-samples t-tests, paired-samples t-tests, Cohen's d effect size calculation, simple linear regression, and thematic analysis. Post-test results showed a statistically significant advantage for the experimental group (M = 68.5, SD = 10.2) over the control group (M = 53.2, SD = 12.4; t(80) = 6.12, p < 0.001, Cohen's d = 1.36). Within-group analysis confirmed significant pre-test to post-test improvement in the experimental group (t = 14.23, p < 0.001) but not in the control group. Students in the experimental group reported consistently positive perceptions of PBL across all measured dimensions. Linear regression confirmed that student perceptions of PBL significantly predicted academic achievement (R² = 0.32, p < 0.001). Teacher interviews identified enhanced student engagement and improved conceptual understanding as primary benefits, while limited laboratory resources and class management complexity were identified as implementation challenges. The study concludes that PBL is a pedagogically effective and CBC-aligned strategy for electrolysis instruction in Rwandan secondary schools and recommends its systematic integration into chemistry teacher professional development programs.