PENERAPAN MODEL PEMBELAJARAN PROBLEM SOLVING UNTUK MELATIHKAN KETERAMPILAN BERPIKIR KRITIS PADA MATERI LAJU REAKSI KELAS XI SMA (IMPLEMENTATION PROBLEM SOLVING LEARNING MODEL TO TRAIN CRITICAL THINKING SKILLS ON REACTION RATE IN SENIOR HIGH SCHOOL GRADE XI) - AYU DIAN PRATIWI, GALUH (Universitas Negeri Surabaya, 2018)