The aim of this research is to describe the effectiveness of predict-observe-explain (POE) learning model in reaction rate concept to enhance giving reasons skill.  Students who became the subject of this research was XI grade of Science 1 Bandar Lampung Senior High School in Bandar Lampung Academic Year 2012/2013.  This research used the pre-experimental method and one group pretest-posttest design.  The effectiveness of POE learning model was determined based on the average value of n-Gain.  The results of this research showed that the average value of n-Gain of giving reasons skill was 0,66.  Thus, it can be concluded that the POE learning model in reaction rate concept effective to enhance giving reasons skill in medium category.Penelitian ini bertujuan untuk mendeskripsikan efektivitas model pembelajaran predict-observe-explain (POE) pada materi laju reaksi dalam meningkatkan keterampilan memberikan alasan. Subyek dalam penelitian ini adalah siswa SMA Negeri 6 Bandar Lampung kelas XI IPA1 Tahun Ajaran 2012-2013.  Penelitian ini menggunakan metode pre-experimental dengan One-Group Pretest-Posttest Design.  Efektivitas model pembelajaran POE diukur berdasarkan nilai n-gain. Hasil penelitian menunjukkan bahwa rata-rata nilai n-gain keterampilan memberikan alasan sebesar 0,66. Dapat disimpulkan bahwa pembelajaran POE pada materi laju reaksi efektif dalam meningkatkan keterampilan memberikan alasan dengan kriteria sedang.Kata kunci: keterampilan memberikan alasan, laju reaksi, pembelajaran POE.
                        
                        
                        
                        
                            
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