<![CDATA[This research was aimed to describe the practicality, effectiveness, and effect size of discovery learning model to improve fluency thinking skill of buffer solution topics. This research used poor experimental method with one group pretest-posttest design. Students of SMAN 1 Gadingrejo for 2016/2017 academic years at XI IPA 1 class was used as sample which it was obtained by using cluster random sampling. Practicality was measured by implementation of discovery learning model and students response. Effectiveness was measured by basis of teacher ability, students activity, and the students skill of fluent thinking and effect size measurement. The results showed that discovery learning model was practice, effective, and has big effect size in improve fluency thinking skill of buffer solution topics.Penelitian ini bertujuan untuk mendeskripsikan kepraktisan, keefektivan dan ukuran pengaruh model discovery learning dalam meningkatkan keterampilan berpikir lancar peserta didik pada materi larutan penyangga. Penelitian ini menggunakan metode poor experimental dengan one group pretest-posttest design. Peserta didik SMAN 1 Gadingrejo tahun pelajaran 2016/2017 di kelas XI IPA 1 digunakan sebagai sampel yang diperoleh dengan menggunakan cluster random sampling. Kepraktisan ditentukan berdasarkan keterlaksanaan model discovery learning dan respon peserta didik. Keefektivan ditentukan berdasarkan kemampuan guru, aktivitas peserta didik, dan kemampuan berpikir lancar peserta didik dan uji ukuran pengaruh. Hasil penelitian menunjukkan bahwa model discovery learning praktis, efektif dan memiliki ukuran pengaruh yang besar dalam meningkatkan keterampilan berpikir lancar peserta didik pada materi larutan penyangga.Kata kunci: discovery learning, keterampilan berpikir lancar, larutan penyangga]]>
