Jurnal Akademika Kimia
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The Ability of Chemistry Problem Solving of Senior High School Students in Palu Sulawesi Tengah
Get PDFThe research is purposed to describe the problem-solving ability of the Senior High School XI grader students in Palu city. The measurement of the problem-solving ability could be determined by solving the exercises of Hydrocarbon and Thermochemistry topics using the Polya’s sequences; consisting of understanding the problem, devising, doing the plan, and evaluating. The ability of students’ problem solving is classified well in every sequence in case of the number of high category students is 60%. The samples are 240 of 507 XI grade students learning chemistry in SMAN 3 and SMA Madani Terpadu in Palu City. The data of problem-solving is determined by providing a test in the form of a validated assay. The result shows the average of XI graders in Palu City only capable of solving the problem without understanding, devising, and evaluating while solving hydrocarbon topics. The ability is not even possessed by students in Thermochemistry. It implies that senior high school students in Palu could not represent the problem in the form of figure, symbol, statement, and mathematics statement or have not been able to devise the problem solving and correlate the obtained result with the related theory or concept. Therefore, the students should be trained to solve the problem in learning by application the problem-solving sequences
Implementation of Guided Inquiry Learning Model on Colloid Systems to Improve Critical Thinking Ability of Students
Get PDFCritical thinking is the ability to solve problems through an investigation so as to produce conclusions or rational decisions. This study aimed to obtain an improvement of critical thinking skills of students in Grade XI at SMAN 3 Palu after the implementation of the guided inquiry learning model on Colloid Systems. This study was a pre-experiment with one group pretest-posttest design. The sample was run by simple random sampling with the sample of Class XI Science 1 as the replication class 1 (n = 36) and Class XI Science 3 as the replication class 2 (n = 35). Data on students' critical thinking was taken using tests that were given before and after learning. An improvement in students' critical thinking skills in replication class 1 and replication class 2 was by 50%. Data of students' critical thinking skills were tested using non-parametric statistical analysis, namely the Mann-Whitney test. The test results obtained the Zh value -0.076, so -1.96 ≤ -0.076 ≤ +1.96. This result is in the reception area of Ho, and H1 is rejected. It means that the average score of critical thinking ability of students in the replication class 1 is the same as in replication class 2. This study concluded that the implementation of the guided inquiry learning model on Colloid Systems improves the critical thinking skills of students in Grade XI at SMAN 3 Palu
Copigmentation of Flavonoids of the Gadung Mango Bark (Mangifera Sp) as a Coloring Substance
Get PDFFlavonoids are pigments in the gadung mango bark that produce a yellow color. The research on copigmentation of flavonoids from gadung mango bark (Mangifera sp) as coloring agents was carried out by the maceration method using 96% ethanol. The extract obtained was concentrated using a vacuum rotary evaporator at 40 oC. The study aimed to determine levels of flavonoids and stability of color gadung mango bark on the inner and outer of the result copigmentation as a coloring agent. Measurement of total flavonoid levels at a wavelength of 520 nm and 700 nm using UV-Vis spectrophotometry. The results of this study indicate that the total flavonoids levels in the inner and outer gadung mango bark samples were 0.162 mg/g and 0.359 mg/g, respectively. The color stability of flavonoids of the gadung mango bark inside and outside as the results of copigmentation was stable at the temperature 35 oC and the results obtained in the color stability test of the hero cloth through washing soap water was with a 0 day in 5 hours
Analysis of Calcium (Ca) Levels in Milkfish’s (Chanos chanos) Bone Using Atomic Absorption Spectrophotometry (AAS)
Get PDFMilkfish (Chanos chanos) is famous for Indonesian and has high economic value. Milkfish bone can be processed into flour. A milkfish bone sample was obtained from the Sioyong Market in Dampelas, Donggala. The purpose of this study was to determine the calcium (Ca) levels in milkfish bone using atomic absorption spectrophotometry (AAS). The sample preparation method used dry destruction with sample ignition. The results showed that the average calcium levels in the flesh and head bones of milkfish aged two months were 0.052 ± 0.0007% and 0.132 ± 0.0056%, while those at aged five months milkfish were 0.197 ± 0.0014% and 0.138 ± 0 0007%, respectively. This study concludes that the older the age of milkfish is, the higher the calcium levels in the bones
Analysis of Cyanide Contents in Cassava Leaves (Manihot esculenta Crantz) Based on Boiling Time with Formation of Hydrindantin Complex by Using UV-Vis Spectrophotometry
Get PDFThis study aimed to determine cyanide contents in cassava leaves (Manihot esculenta Crantz) based on boiling time with the formation of hydrindantin complex using UV-Vis spectrophotometry. The variation of boiling time was 0, 5, 10, and 15 minutes respectively. The cyanide content was prepared by extracting the sample using water for 2 hours. Then the sample was distilled to obtain a distillate that containing cyanide. Determination of cyanide was carried out by reacting samples containing cyanide with 1% ninhydrin and 0.5% Na2CO3, then adding 1 M NaOH to form blue hydrindantin compounds in an alkaline condition. Blue hydrindantin compounds formed were analyzed by spectrophotometry at a maximum wavelength of 590 nm. The results showed that cyanide contents in cassava leaves based on boiling time 0, 5, 10, and 15 minutes respectively were 20.73 ppm, 13.92 ppm, 9.18 ppm, and 3.38 ppm. The longer the cassava leaves were boiled, the better it was to be consumed because it will significantly reduce cyanide contents
Co-pigmentation of Anthocyanin Jamblang Fruit (Syzygium cumini) with Acetic Acid and Alum
Get PDFThis study aimed to determine the effect of temperature on the stability of anthocyanin jamblang after co-pigmentation with acetic acid and alum. The extraction of Jamblang fruit used the maceration method with n-hexane, ethyl acetate, and ethanol-HCl 0.5% solvents. The total anthocyanin obtained was 70.64 mg/L. Anthocyanin of jamblang fruit was co-pigmented with acetic acid and alum in a concentration of 2.5%; 5%; 7.5%; and 10%, then be heated at various temperatures and heating times. At a temperature of 80 ℃ for 150 minutes, every 30 minutes, absorbance was measured. At a temperature of 60 ℃, the heating was carried out for 225 minutes, and every 45 minutes, absorbance was measured. At a temperature of 40 ℃, the heating was carried out for 300 minutes, and every 60 minutes, absorbance was measured. Absorbance measurements were taken using a UV-VIS spectrophotometer. The results showed that co-pigmentation of anthocyanin occurred proved by shifting λ max from 470 nm (unco-pigmented extract) to 500 nm (co-pigmented extract acetic acid) and 540 nm (co-pigmented extract alum). Acetic acid and alum co-pigments maintained the stability of anthocyanin jamblang at a heating temperature of 60 ℃. It can be seen from decreased absorbance, which is not so significant compared to the decrease at temperatures of 40 and 80 ℃, accompanied by anthocyanin's fading color, which is co-pigmented with acetic acid and alum during the heating process
Developing Senior High School Student’s Chemical Literacy Skills Through Inquiry-Based Online Chemistry Learning
Get PDFThis paper is motivated by the challenges of chemistry class during the online learning period in developing students’ chemical literacy skills that were found during internship two by the author at a school in North Sulawesi at Senior High School. Based on these activities, it is known that the limitations of students in understanding chemical materials and concepts during online learning pose as a challenge for teachers to carry out the chemistry lessons long distanced. This paper aims to review the development of students’ literacy skills through inquiry-based learning. This paper also aims to examine the implications of chemical literacy in helping Christian teachers guide students to God's wisdom through inquiry-based chemistry’s online learning. The results from this study showed that the chemical literacy skills of students in the school where the author carried out field experience program two activities showed positive results; however, it was not comprehensive. Furthermore, chemical literacy helped Christian teachers observe students’ development in understanding chemical concepts and their relevance to biblical principles. This study concluded that honing chemical literacy skills through inquiry-based online learning can help students be more active in obtaining information. Good chemical literacy skills will help students make decisions based on problems that are always based on biblical principles. The author of this study suggests examining strategies in addition to inquiry-based learning, which can improve student’s chemical literacy skills, especially in online chemistry learning
Antioxidant Activity Test of Acetone and Ethanol Extracts of Cocoa (Theobroma cacao L.) Beans Husk
Get PDFCocoa beans husk is waste produced from the cocoa processing industry containing alkaloid, flavonoid, tannin, saponin, and triterpenoid compounds. This material has the potential to be used as a source of natural antioxidant compounds. This study aimed to determine the antioxidant activity of cacao beans husk extracts by comparing acetone and ethanol as solvents through the extraction process. This antioxidant activity was determined using the DPPH (1,1-diphenyl-2-picrylhydrazyl) test method measured by UV-Vis spectrophotometer after adding an extract of cocoa beans husk. The positive control was vitamin C, while the negative control was DPPH solution dissolved in ethanol. The results showed that the extract of cacao beans husk has more potent antioxidant activity with a lower IC50 value of 181.2 ppm, while the acetone extract has an IC50 value of 247.9 pp
The Differences of Chemistry Learning Outcome Through the Implementation of Think-Talk-Write (TTW) Type of Cooperative Learning Model and Scramble Type in Teaching Atomic Structure
Get PDFThis research aimed to determine the differences of chemistry learning outcome through the implementation of scramble type of cooperative learning model and think-talk-write (TTW) type in teaching atomic structure at class XI of SMA Negeri 1 Pamona Selatan. This research was a quasi-experiment with a non-randomized pretest-posttest control group design. It was conducted by arranging two groups in which class XI Natural Science 1 as experimental group 1 (n = 21) and class XI Natural Science 2 as experimental group 2 (n = 20). The data of the research were analyzed using a one-party t-test statistic with the prerequisite test, normality test, and homogeneity. The result of data analysis obtained, X̅1 value of chemistry learning on the students of experimental class 1 was 79.86 (SD = 7.15), whereas in the experimental class 2 students X̅2 value was 73.95 (SD = 8. 26). The result of hypothesis testing was obtained t > t1 - α was 2.55> 1.68 with significant level (α = 0.05) and degrees of freedom = 42. This showed that Ho was rejected and Ha was accepted so that it can be concluded that there were differences in chemistry learning outcome through the implementation of scramble type of cooperative learning model and think-talk-write (TTW) type in teaching atomic structure at class XI of SMA Negeri 1 Pamona Selatan
Concentration Effect of Watermelon Skin Extracts (Albedo) as Organic Inhibitors on the Corrosion of Iron Nails in 3% NaCl Medium Solution
Get PDFThis study aimed to determine the concentration effect of skin extract in watermelon on the inhibition of corrosion rates of iron nails in the corrosive medium of NaCl solution and seawater as a comparison. The study began with the first maceration of the skin in watermelon and then followed by evaporation to produce extracts specific gravity 0,097 gram/mL as inhibitors with variations in concentrations of 1, 2, 4, 8, and 16%. The method of determining the corrosion rate used was the weight loss method from the 7-day immersion process. The results showed that the greatest corrosion inhibition efficiency occurred at a concentration of 8% for immersion with 3% NaCl corrosive medium and 4% concentration for immersion in seawater with the efficiency of 11.56% and 22.15%, respectively. Based on the results of the study, it was found that each addition of extract in watermelon can affect the effectiveness of inhibition