<![CDATA[The research was aimed to describe the practicality, effectiveness and effect size of discovery learning to improve students mental model and concept mastery on electrolyte and non electrolyte solution topic. This research has been done at SMA N 16 Bandar Lampung for 2016/2017 academic year. The research one group pretest-posttest design by using cluster random sampling and obtained class X.7 as sample of 330 students. The data were analyzed descriptively. Practicality was determined from implementation of RPP and student response. Effectiveness was determined from teacher's ability, student activities, improvement mental model and students concept mastery. The results of this research showed that the practicality and effectiveness of discovery learning had very high criteria and had large effect size. Based on it, the conclution that discovery learning was practical, effective, and had large effect to improve mental model and students concept mastery.Penelitian dengan tujuan mendeskripsikan kepraktisan, keefektifan, dan ukuran pengaruh pembelajaran discovery learning dalam meningkatkan model mental dan penguasaan konsep siswa pada materi larutan elektrolit dan non elektrolit. Penelitian ini dilakukan di SMAN 16 Bandar Lampung Tahun Ajaran 2016/2017. Penelitian one group pretest-posttest design dengan teknik cluster random sampling dan diperoleh kelas X.7 sebagai sampel populasi 330 siswa. Data dianalisis secara deskriptif. Kepraktisan ditentukan dari keterlaksanaan RPP dan respon siswa. Keefektifan ditentukan dari kemampuan guru, aktivitas siswa, peningkatan model mental dan penguasaan konsep siswa. Hasil penelitian menunjukkan pembelajaran discovery learning memiliki kepraktisan dan keefektifan dengan kriteria sangat tinggi dan ukuran pengaruh yang besar. Kesimpulan penelitian ini yaitu pembelajaran discovery learning praktis, efektif, dan memiliki pengaruh yang besar dalam meningkatkan model mental dan penguasaan konsep siswa.Kata Kunci: discovery learning, model mental, penguasaan konsep.]]>
