THE EFFECT PROBLEM BASED LEARNING ASSISTED BY QUESTION CARDS ON CRITICAL THINGKING SKILLS ON ADDITIVE AND ADDICTIVE SUBSTANCES FOR VIII GRADE STUDENTS OF SMPN 38 PADANG. universe [Internet]. 2024 Jun. 30 [cited 2026 Aug. 13];5(1):51-7. Available from: http://universe.ppj.unp.ac.id/index.php/universe/article/view/585