Analisis Kemampuan Pemahaman Konsep Siswa Pada Materi Persamaan Garis Lurus

Pemahaman konsep sangat berguna dalam penyelesaian masalah. Tujuan penelitian adalah untuk mendeskripsikan kemampuan pemahaman konsep siswa kelas VIII SMP Negeri 1 Toma pada materi persamaan garis lurus. Jenis penelitian adalah penelitian kualitatif dengan pendekatan deskriptif. Sumber informan yaitu: siswa kelas VIII SMP Negeri 1 Toma dengan jumlah 33 orang. Teknik analisis data yaitu: reduksi data, penyajian data dan penarikan kesimpulan. Teknik pengumpulan data yaitu: tes dan wawancara tidak terstruktur. Berdasarkan hasil penelitian dan pembahasan diperoleh bahwa kemampuan pemahaman konsep matematis dengan kategori Sangat Baik (SB) berada pada 12%, kategori Baik (B) berada 21%, kategori Cukup (C) berada pada 27%, kategori Kurang (K) berada pada kategori 33%, kategori Sangat Kurang (SK) berada 6%. Sehingga kemampuan pemahaman konsep matematika lebih dominan pada kategori Kurang (K) sebesar 33%. Peneliti menyarankan agar guru dapat membangkitkan kemampuan pemahaman konsep matematis siswa dalam kegiatan pembelajaran.

Kinetics of Photochemical Reactions of Thionine

Hie photochemical reduction of thionine by N-phenyl glycine, N-allylurea, N -phonylurea and thiourea in absolute me¬ thanol ms investigated. An apparatus for the irradiation of air free solutions, with known intensities of monochromatic light was constructed. Double walled glass reaction cell was deviced in which nitrogen inlet/outlet, water inlet/outlet ar¬ rangements were made. Acidities of the reaction solutions were controlled using buffer solutions. Acidities determined spec- trophotometrically using basic indicator were expressed in terms of a Hamnett acidity function. Variations of quantum ef¬ ficiencies in absolute methanol have been determined at various concentrations of thionine, reductants, and acidities. The oxy¬ gen free reaction solutions were irradiated and the react ions were followed by measuring the intensity of light transmitted. The quantum efficiency, in yellow light, for the dis¬ appearance of thionine, was found to be a function of reductant concentration, acidity and temperature. The quantum efficiency was found to be independent of the concentration of thionine. The results have been interpreted in terms of a reaction mechanism Ratios of the certain rate constants for the proposed mec banian have been evaluated. It was found that the quantum efficiency is controlled by two equilibriums between: i) triplet state of thionine with proton, and protonated triplet state of thionine, and ii) protonated triplet state of thionine with reductant, and associated complex of thionine with reductant.