Pengaruh Model Pembelajaran Cooperative Script dengan Media Kartu Gambar Terhadap Minat dan Hasil Belajar Siswa pada Materi Perkembangan Model Atom

Penelitian ini bertujuan untuk mengetahui pengaruh model Cooperative Script dengan media kartu gambar terhadap minat dan hasil belajar siswa pada materi perkembangan model atom kelas X IPA. Jenis penelitian yang digunakan adalah pre experimental design dengan desain one group pretest-posttest design. Penelitian ini dilakukan di SMA Negeri 1 Peusangan. Populasi dalam penelitian ini adalah seluruh siswa kelas X IPA SMA Negeri 1 Peusangan. Pengambilan sampel menggunakan teknik purposive sampling sehingga yang menjadi sampel penelitiannya adalah siswa kelas X IPA 2 dengan jumlah 24 siswa. Teknik pengumpulan data menggunakan tes yang terdiri dari soal pretest, posttest, dan angket. Berdasarkan hasil penelitian, rata-rata hasil pretest siswa sebesar 35,63 dan rata-rata hasil posttest siswa sebesar 78,33. Data pretest dan posttest diuji normalitas dengan hasil < 0,05 yang menyatakan bahwa data tidak berdistribusi normal, kemudian dilanjutkan dengan uji hipotesis melalui teknik Wilcoxon dengan hasil < 0,05 yang membuktikan bahwa Ha diterima. Sedangkan penilaian angket minat belajar diperoleh hasil persentase rata-rata minat belajar siswa yaitu 73,33% dengan kategori baik. Dengan demikian dapat disimpulkan bahwa model Cooperative Script dengan media kartu gambar mempengaruhi minat dan hasil belajar siswa pada materi perkembangan model atom kelas X IPA SMA Negeri 1 Peusangan.

Peningkatan Hasil Belajar dan Aktivitas Siswa pada Materi Perkembangan Model Atom Melalui Model Pembelajaran Discovery Learning (DL)

Penelitian ini bertujuan untuk mengkaji sejauh mana model pembelajaran Discovery Learning (DL)”.dapat meningkatkan hasil belajar dan aktivitas siswa. Subjek penelitian ini adalah siswa kelas X.IPA-2 semester 1 tahun Tahun 2020 yang berjumlah 25 siswa, terdiri dari 13 siswa putra dan 12 siswa putri. Penelitian ini berlangsung dalam 2 siklus yang masing-masing siklus terdiri atas tahap perencanaan, tindakan, observasi, dan refleksi. Data yang diperoleh dalam penelitian ini meliputi: hasil belajar siswa yang diambil dari pemberian soal tes pada akhir siklus, kemampuan guru dalam pembelajaran yang diambil dari lembar observasi, aktivitas siswa dalam pembelajaran yang diambil dari lembar observasi, dan data tentang refleksi siswa terhadap pembelajaran yang diambil dari angket pada setiap akhir pertemuan. Indikator keberhasilan pada penelitian ini adalah: (1) apabila≥ 70% dari jumlah siswa berkategori tuntas dengan criteria tuntas belajaran apabila nilai hasil evaluasi pada siklus I,II, ≥ 65, (2) apabila aktivitas siswa dalam pembelajaran≥ 70% yang diukur dengan melihat lembar observasi siswa. Hasil penelitian pada siklus I menunjukkan rata-rata hasil belajar siswa sebesar 58,75 dan persentase ketuntasan belajar sebesar 60,71%. Aktivitas siswa 63,64%, persentase kemampuan guru 73,44 %. Sedangkan hasil penelitian pada siklusII rata-rata hasil belajar siswa sebesar 66,25 dan persentase ketuntasan belajar sebesar71,43%. Aktivitassiswa 75,00%, dan persentase kemampuan guru sebesar 84,37%. Dari penelitian ini diperoleh kesimpulan bahwa dengan menggunakan model pembelajaran Discovery Learning (DL) dapat meningkatkan hasil belajar kimia dan aktivitas siswa kelas X IPA-2 semester 1 tahun pelajaran 2020/2021 pada materi perkembangan model atom.

DESAIN DAN UJI COBA VIDEO STOP MOTION SEBAGAI MEDIA PEMBELAJARAN PERKEMBANGAN TEORI MODEL ATOM

This research was instigated by student difficulty in comprehending chemistry lesson that was theoretical, recitation and the lack of using instructional media. This research aimed at knowing the feasibility result of Stop Motion video as an instructional media especially on media lesson theoretical and recitation at State Vocational High School through validity test and practicality test. In this research Stop Motion video was designed by using Filmora application to support the learning on Development of Atomic Model Theory lesson. The final product was in the form of a valid tutorial video. It was a research and development (R&D) using model of Borg and Gall modification, and it was carried out at State Vocational High School 7 Pekanbaru. Interview and questionnaire were conducted for the techniques of collecting data. Stop Motion video as an instructional media developed was tested valid with 88.95% percentage (very valid) and practical with 82.75% (very practical). Based on these findings, it could be concluded that Stop Motion video as an instructional media on Development of Atomic Model Theory lesson have been valid and practical, and it got good student responses, so it could be tested in the next phase.

Non-local thermodynamic equilibrium line formation for Si i–ii–iii in A–B stars and the origin of Si ii emission lines in ι Her

ABSTRACT A comprehensive model atom was developed for Si i–ii–iii using the most up-to-date atomic data available so far. Based on non-local thermodynamic equilibrium (NLTE) line formation for Si i, Si ii and Si iii and high-resolution observed spectra, we determined the NLTE abundances for a sample of nine unevolved A9–B3 type stars with well-determined atmospheric parameters. For each star, NLTE reduces the line-to-line scatter for Si ii substantially compared with the LTE case and leads to consistent mean abundances from lines of different ionization stages. In the hottest star of our sample, ι Her, Si ii is subject to overionization that drives emission in the lines arising from the high-excitation doublet levels. Our NLTE calculations reproduced 10 emission lines of Si ii observed in ι Her. The same overionization effect leads to greatly weakened Si ii lines, which are observed in absorption in ι Her. Large positive NLTE abundance corrections (up to 0.98 dex for 5055 Å) were useful for achieving consistent mean abundances from lines of the two ionization stages, Si ii and Si iii. It was found that NLTE effects are overestimated for the Si ii 6347, 6371 Å doublet in ι Her, while the new model atom works well for cooler stars. At this stage, we failed to understand this problem. We computed a grid of the NLTE abundance corrections for lines of Si i, Si ii and Si iii in model atmospheres with effective temperatures and surface gravities characteristic of unevolved A–B type stars.

The 3D non-LTE solar nitrogen abundance from atomic lines

Nitrogen is an important element in various fields of stellar and Galactic astronomy, and the solar nitrogen abundance is crucial as a yardstick for comparing different objects in the cosmos. In order to obtain a precise and accurate value for this abundance, we carried out N I line formation calculations in a 3D radiative-hydrodynamic STAGGER model solar atmosphere in full 3D non-local thermodynamic equilibrium (non-LTE). We used a model atom that includes physically motivated descriptions for the inelastic collisions of N I with free electrons and with neutral hydrogen. We selected five N I lines of high excitation energy to study in detail, based on their strengths and on their being relatively free of blends. We found that these lines are slightly strengthened from non-LTE photon losses and from 3D granulation effects, resulting in negative abundance corrections of around − 0.01 dex and − 0.04 dex, respectively. Our advocated solar nitrogen abundance is log ɛN = 7.77, with the systematic 1σ uncertainty estimated to be 0.05 dex. This result is consistent with earlier studies after correcting for differences in line selections and equivalent widths.

Observational constraints on the origin of the elements

Context. The pursuit of more realistic spectroscopic modelling and consistent abundances has led us to begin a new series of papers designed to improve current solar and stellar abundances of various atomic species. To achieve this, we have begun updating the three-dimensional (3D) non-local thermodynamic equilibrium (non-LTE) radiative transfer code, MULTI3D, and the equivalent one-dimensional (1D) non-LTE radiative transfer code, MULTI 2.3. Aims. We examine our improvements to these codes by redetermining the solar barium abundance. Barium was chosen for this test as it is an important diagnostic element of the s-process in the context of galactic chemical evolution. New Ba II + H collisional data for excitation and charge exchange reactions computed from first principles had recently become available and were included in the model atom. The atom also includes the effects of isotopic line shifts and hyperfine splitting. Methods. A grid of 1D LTE barium lines were constructed with MULTI 2.3 and fit to the four Ba II lines available to us in the optical region of the solar spectrum. Abundance corrections were then determined in 1D non-LTE, 3D LTE, and 3D non-LTE. A new 3D non-LTE solar barium abundance was computed from these corrections. Results. We present for the first time the full 3D non-LTE barium abundance of A(Ba) = 2.27 ± 0.02 ± 0.01, which was derived from four individual fully consistent barium lines. Errors here represent the systematic and random errors, respectively.

Superadiabatic Forces via the Acceleration Gradient in Quantum Many-Body Dynamics

We apply the formally exact quantum power functional framework (J. Chem. Phys. 2015, 143, 174108) to a one-dimensional Hooke’s helium model atom. The physical dynamics are described on the one-body level beyond the density-based adiabatic approximation. We show that gradients of both the microscopic velocity and acceleration field are required to correctly describe the effects due to interparticle interactions. We validate the proposed analytical forms of the superadiabatic force and transport contributions by comparison to one-body data from exact numerical solution of the Schrödinger equation. Superadiabatic contributions beyond the adiabatic approximation are important in the dynamics and they include effective dissipation.

Ca line formation in late-type stellar atmospheres

Context. Departures from local thermodynamic equilibrium (LTE) distort the calcium abundance derived from stellar spectra in various ways, depending on the lines used and the stellar atmospheric parameters. The collection of atomic data adopted in non-LTE (NLTE) calculations must be sufficiently complete and accurate. Aims. We derive NLTE abundances from high-quality observations and reliable stellar parameters using a model atom built afresh for this work, and check the consistency of our results over a wide wavelength range with transitions of atomic and singly ionised calcium. Methods. We built and tested Ca I and Ca II model atoms with state-of-the-art radiative and collisional data, and tested their performance deriving the Ca abundance in three benchmark stars: Procyon, the Sun, and Arcturus. We have excellent-quality observations and accurate stellar parameters for these stars. Two methods to derive the LTE/NLTE abundances were used and compared. The LTE/NLTE centre-to-limb variation (CLV) of Ca lines in the Sun was also investigated. Results. The two methods used give similar results in all three stars. Several discrepancies found in LTE do not appear in our NLTE results; in particular the agreement between abundances in the visual and infra-red (IR) and the Ca I and Ca II ionisation balance is improved overall, although substantial line-to-line scatter remains. The CLV of the calcium lines around 6165 Å can be partially reproduced. We suspect differences between our modelling and CLV results are due to inhomogeneities in the atmosphere that require 3D modelling.

Surface abundances of CNO in Galactic O-stars: a pilot study with FASTWIND

Context. Rotational mixing is known to significantly affect the evolution of massive stars; however, we still lack a consensus regarding the various possible modeling approaches and mixing recipes describing this process. The empirical investigation of surface abundances of carbon, nitrogen, and oxygen (CNO) in large samples of O- and B-type stars will be essential for providing meaningful observational constraints on the different available stellar evolution models. Aims. Setting up and testing adequate tools to perform CNO surface abundance determinations for large samples of O-type stars, by means of the fast performance, NLTE, unified model atmosphere code FASTWIND. Methods. We have developed a set of semi-automatic tools for measuring and analyzing the observed equivalent widths of strategic optical C, N, and O lines from different ions. Our analysis strategy is based on a χ2 minimization of weighted differences between observed and synthetic equivalent widths, the latter computed from tailored model grids. We have paid special attention to the (significant) errors introduced by typical uncertainties in stellar parameters. In this pilot study, we describe these tools, and test their performance and reliability using a set of high quality spectra of a sample of 18 presumably single Galactic O-type stars with low projected rotational velocities (v sin i≲100 km s−1), and previously determined stellar parameters. In particular, we have compared the outcome of our analysis with results from existing studies and theoretical stellar evolution models. Results. Most of our results for carbon and nitrogen agree, within the errors, with both theoretical expectations and literature values. While many cooler dwarfs display C and N abundances close to solar, some of the early- and mid-O dwarfs – and most supergiants – show significant enrichment in N and depletion in C. Our results for oxygen in late-O dwarfs are, however, unexpectedly low, possibly indicating deficiencies in the adopted oxygen model atom. For all other objects, no systematic problems in their oxygen content have been identified. Specific stars in our sample show peculiarities in their abundances, and we suggest hypotheses regarding their origin. Conclusions. Our method is (almost) ready to be applied to large samples of late and mid O-type stars – although the oxygen model atom needs to be improved and carefully tested first. For early O-type stars (O4 and hotter), a simultaneous UV analysis seems to be inevitable, due to the scarcity and weakness of optical C and O lines. This will necessarily imply a more complex modeling, additionally accounting for the effects of X-rays from wind-embedded shocks and wind inhomogeneities.