Saluat Siahaan. IMPROVE COLLIGATIVE PROPERTIES SKILLS AND PROBLEM SOLVING ABILITY OF SMA NEGERI 1 BABALAN CLASS XII STUDENTS USING MODEL PROBLEM BASED LEARNING (PBL). IJEL [Internet]. 2023 Aug. 30 [cited 2025 Apr. 17];2(2):21-38. Available from: https://ijel.asia/index.php/ijel/article/view/70