<![CDATA[This research was aimed to describe the effectiveness of learning by using the scientific approach in acid base subject matter in increasing the student’s flexibility thinking skills. The population in this research was students of grade X1 Science class SMA Negeri 3 Metro in the Academic Year 2013-2014. Sampling was done by purposive sampling technique and obtained X13 and X15 as research classes. The method of the research was quasi experimental with Non Equivalent Control Group Design. The effectiveness of scientific approach was showed by the significant difference of n-gain score between control and experiment class. The result showed that the n-gain average of student’s flexibility thinking skills for control class and experiment class were 0,33 and 0,54 respectively. From hypothesis testing was known that scientific approach was effective in increasing student’s flexibility thinking skills. Penelitian ini bertujuan untuk mendeskripsikan efektivitas pembelajaran dengan menggunakan pendekatan saintifik pada materi asam basa dalam meningkatkan keterampilan berpikir luwes siswa. Populasi dalam penelitian ini adalah siswa kelas XI IPA SMA Negeri 3 Metro Tahun Pelajaran 2013-2014. Pengambilan sampel dilakukan dengan teknik purposive sampling dan didapatkan kelas XI IPA3dan XI IPA5 sebagai kelas penelitian. Penelitian ini menggunakan metode kuasi eksperimen dengan Non Equivalent Control Group Design. Efektivitas pendekatan saintifik ditunjukkan berdasarkan perbedaan n-gain yang signifikan antara kelas kontrol dan kelas eksperimen. Hasil penelitian menunjukkan bahwa rata-ratan-gain keterampilan berpikir luwes siswa pada kelas kontrol sebesar 0,33 dan pada kelas eksperimen sebesar 0,54. Berdasarkan pengujian hipotesis, disimpulkan bahwa pendekatan saintifik efektif dalam meningkatkan keterampilan berpikir luwes siswa.Kata kunci: keterampilan berpikir luwes siswa, materi asam basa, pembelajaran menggunakan pendekatan saintifik]]>
