This research was carried out to reveal prospective chemistry teachers’ understanding in rate of reaction concept. A survey with a quantitative approach study was conducted toward 61 of prospective chemistry teachers who were taking a basic chemistry course. Data were obtained using a true and false test which containing 30 questions related to the rate of reaction topic. They were categorized into five concepts covering rate of reaction basic concept, rate of reaction law, collision theory, factors that affect the rate of reaction, and reaction mechanism concept are 3, 4, 3, 14, and 6 questions respectively. The results proved that most of them had a low understanding in the rate of reaction concept, especially on the first concept but in the concept of collision theory they had a relatively high understanding. The efforts are needed by them as prospective chemistry teachers to increase their understanding of the rate of reaction concept. However, this research did not explore their description in explaining about the concept. Therefore, there is a need for further research to discuss the mental models of prospective chemistry teachers in the rate of reaction concept understanding.
This study aims to determine the concentration of cadmium (Cd) metal content in various facial moisturizing creams with atomic absorbtion spectrophotometry (AAS). Samples were analyzed in the form of 6 brands of facial moisturizer cream that sold in market and selected randomly. The cream samples were destructed by wet destruction method. Next, the samples of destruction result were analyzed by atomic absorbtion spectrophotometry method with wavelength about 228.8 nm to determine the concentration of cadmium. The results of this research showed that there was cadmium (Cd) metal content in the 2 samples of facial moisturizing cream that analyzed. Cadmium metal concentration on brand A is 0.1389 ± 2.7817 x 10-3 ppm and and brand B is 0.1321 ± 2.6468 x 10-3 ppm. Based on this result, the moustirizing creams are safe to use due to the BPOM regulation
This descriptive content analysis study was carried out to review students and pre-service teachers ' mental model of chemistry concepts. This study was motivated by difficulties experienced by students and teachers in the process of learning chemistry. This study put on criteria with specific keyword about a mental model in chemistry concepts and a period of 2009 till 2019 which relevant databases yielded a total of 66 articles. This study covers 41 qualitative studies, 18 quantitative studies, and this remains mix method studies. Article ' s aspects focused on such parameters as aim, method, sample, data collection tool, data analysis, chemistry concept, mental model theory, and recommendation of studies. Using content analysis, as a result was known that most studies used qualitative methods with a variety of data collection tools and data analysis techniques. Moreover, these mental models studies were mostly involved students who learned inorganic chemistry. General conclusions from this study in the importance form of the mental model exploration to master the chemistry concepts and this is intended to improve the chemistry learning process. This research also implies to do good innovative changes in various aspects to improve their scientific mental model. These changes include to innovate classroom practices, further researches, curriculum policy, and learning media developer.
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