Critical thinking skills are one of the 21st century skills that are effectively trained by using the OR-IPA and Problem Based Learning (PBL) Model, therefore this research aims to compare the effectiveness of both. Research design used True Experiment with Randomized Subject Control-group Pre-test and Post-test with 94 pre-service physics teachers. Data collected using the critical thinking skills test and the student response sheet, and then analyzed using t-test and N-gain. The results showed: (1) the teaching instruments of OR-IPA and PBL Model have fulfilled the validity requirements (rα ~ .26) and reliability (α = .96 - .99). (2) Each of OR-IPA, PBL, and Conventional Model can significantly increase critical thinking skills at α = 5%, respectively with average N-gain: medium (.60), medium (.48), and low (.14); with the student response of: very positive, very positive, and less positive. (3) The OR-IPA and PBL Model are effective to improve critical thinking skills, while the Conventional Model is ineffective, and the OR-IPA Model is more effective compared to the PBL Model. Implication of this research is that the OR-IPA Model can be an innovative solution to improve critical thinking skills, but there is still a need for repetitive research like this. Keywords: basic physics, critical thinking skills, OR-IPA model, pre-service physics teachers, and PBL model.

Abstract. Synthesis of Fe 3 O 4 /a-SiO 2 nanoparticle has been conducted based on natural materials by using the co-precipitation method. The used silica was a-SiO 2 collected from silica sand from Bancar Tuban, Indonesia. The Fe 3 O 4 collected from iron sand's Lumajang, Indonesia. The samples was set for Fe 3 O 4 : a-SiO 2 : PEG composition of 1 : 2 : 1. The process was maintained by melting the PEG 4000 and following by adding a-SiO 2 and Fe 3 O 4 . The samples were characterized by using X-Ray Diffractometry (XRD), Transmission Electron Microscopy (TEM), and Fourier Transform Infra-Red (FTIR) spectroscopy. The analysis of the XRD data showed that additional silica into Fe 3 O 4 tended to change the diffraction pattern that represents the existent of both Fe 3 O 4 and silica. The SEM images presented that the samples formed in nanometric size with core-shell structure. Furthermore, the FTIR spectra showed that Si-O-Fe bound appeared at 555-568 cm -1 . Thus, this work was able to produce the Fe 3 O 4 /aSiO 2 nanocomposites by using co-precipitation method in a core-shell structure.

The 2013 curriculum aims to form students who are ready to face the 21st century so that the 2013 curriculum is not only taught about aspects of knowledge but also aspects of skills. Thinking skills are the skills used in the 2013 curriculum, where one of the thinking skills students need is expertise in analytical thinking. These skills are necessary for science learning. Analytical thinking skills can be improved if the teacher trains them correctly, both from the learning model and learning strategies. This study examines learning models and learning tools that can improve analytical thinking skills. Learning based on inquiry learning is expected to improve students' analytical thinking skills. The findings of this study, it is known that inquiry-based models and tools can improve analytical thinking skills because they start from a problem. The problems given are then discussed with the group to find information that fits the situation and find ways to solve the problem nicely by conducting experiments or observations, then summing up the results obtained and communicating them well. Analytical thinking skills are closely related to problem-solving. So with analytical thinking skills, students will quickly identify and solve a problem.

This research aims to improve senior high school students’ physics problem-solving skills through learning used IBMR learning model. This research was a pre-an experimental study with a one-group pre-test and post-test design. The Methods of data collection used validation and test. The materials used to teach were valid category by two experts and can be used to practice physics problem-solving skills. The average post-test score physics problem-solving ability was 73.24 with an N-gain of 0.59 was classified as moderate. The success of IBMR learning model-based devices in practicing problem-solving abilities can be seen in the increase in the average score in each indicator of problem-solving abilities. The indicator of understanding the problem had the highest post-test average score of 94.58 with an N-gain of 0.89 in the high category. The problem-solving indicator had the lowest posttest average score was 58.22 with N-gain 0.39 and mean that it was the moderate category. Based on the results study, it can be concluded that the learning used by IBMR learning model can practice the ability to solve physics problems on heat material and its displacement. Learning with the IBMR learning model was expected to train students in solving physics problems. The stages in the IBMR learning model can help students