Effectiveness of a Flipped Classroom Based on Guided Inquiry Learning System on Acid-Base Solutions

: This study aims to determine the effectiveness of flipped classroom based on guided inquiry learning system on acid-base solutions toward students learning outcomes of XI class senior high school students that had been tested valid and practical. This type of research is quasi-experimental with a Non-Equivalent Control Group Design. The sample class used was XI Mipa 1 as a control class and XI Mipa 2 as an experimental class, with the total of students were 69 using the purposive sampling technique. The instrument used in this study was a multiple choices question to assess students learning outcomes in the cognitive domain. The result of this study to obtain the N-gain value from the experimental class and control class with the values are 0.80 and 0.73, respectively, which indicates the value of experimental class is higher than control class. Furthermore, for the t-test, the value is 3.18, and the t-table value is 1.99. It concludes that using flipped classroom based on guided inquiry learning system on acid-base solutions improve students learning outcomes effectively.


Introduction
The era of the industrial revolution 4.0 (technology disruption era) is an era of transformation in all aspects involving the use of technology through the development of digital system (Rymarczyk, 2020). In line with the story of the industrial revolution, a country's human resources also have quality in terms of critical thinking and problem-solving skills. Efforts that can make to improve human resources are through education. One of the efforts made by the government of the Republic of Indonesia is to roll out the 2013 Curriculum, which aims to equalize global education and remains based on norms (Mawardi et al., 2019).
The Covid-19 pandemic has significantly impacted aspects of life, especially in the field of education. Based on this urgency, the Minister of Education, Culture, Research and Techology of the Republic of Indonesia issued Circular Letter 4 of 2020 regarding the transition from face-to-face learning to technology-based distance learning (Kemendikbud, 2021;Yen, 2020). Other policies are also implemented, such as reducing the allocation of learning time that affecting teachers and students' interactions. Therefore, a learning model is needed to accommodate all learning activities during the pandemic to continue as they should. Blended learning is the one of the solutions that can be used.
Blended learning can combine face-to-face learning and online learning by utilizing interactive electronic technology (Duhaney, 2007). The application of blended learning makes students active inside and outside the classroom. Blended learning combines two learning settings that are synchronous and asynchronous. Synchronous learning is a learning activity between educators and students simultaneously. Asynchronous learning is a learning activity that they can do anywhere and anytime (Chaeruman, 2013). Blended learning has four classifications: rotation model, flex model, self blend, and enriched virtual model. The rotation model consists of four sub-models, one of them is the flipped classroom.
The flipped classroom is a modern learning where students learn the teaching materials before class (online) and discuss it in face-to-face learning (Chaeruman, 2013). In the asynchronous stage, students are learning at home. It will facilitate students with teaching materials that contain models and questions so that students are required to be able to identify, analyze and draw concepts independently. In the synchronous stage, the implementation of learning that will carry out in class will lead to more confirmation actions to educators regarding concepts obtained at the asynchronous stage (Chaeruman, 2013). During the COVID-19 pandemic, students can carry out learning by utilizing a learning management system (LMS) that can optimize the learning process.
LMS is software for activities in the network. The LMS used in this online learning is Edmodo. Edmodo is a free and secure online learning platform (Pedaste et al., 2015). Using Edmodo can help teachers to manage classes and enable students to connect with classmates anywhere and anytime (Balasubramanian et al., 2014;Sapitri, 2021). For flipped classroom-based learning and following the 2013 Curriculum that the learning process is a student-centered, a scientific approach, namely a guided inquiry model .
The inquiry learning model consists by four of submodels that one of them is guided inquiry learning. Guided inquiry learning can stimulate, teach and invite students to think higher to find concepts of the various problems expressed independently, while the teacher's role includes providing learning materials and concerns for guiding students in confirming the ideas (Heather & Randi, 2008;Mawardi et al., 2020). The positive impact of guided inquiry learning on students is making students active in learning by found the concept independently (Mawardi et al., 2020).
One of the essential competencies found in XI class of SMA/MA in even semesters is a basic competence 3.8 regarding acid-base solutions. Students consider it is difficult because the concepts are abstract and have great conceptual difficulties. The concept of acid-base solutions also emphasizes the algorithmic component. In addition, the acid-base solutions also includes three levels of chemistry representation, such as macroscopic, submicroscopic, and symbolic (Sari & Helsy, 2018).
The study that related to flipped inquiry learning (FGIL) as a learning system to overcome the learning problems during the COVID-19 pandemic by utilizing the Edmodo as a LMS on the reaction rate material (Ramadhansyah & Mawardi, 2021) and chemical bonding materials (Syafei & Mawardi, 2022) showed that valid and practical results in the high categories. In addition of using the Edmodo, an open source LMS for flipped guided inquiry learning (FGIL) is Moodle. Moodle has a completer and more adequate menu that is web-based. The existing chemical materials such as salt hydrolysis material (M. U. Sari & Mawardi, 2022) and acid-base materials (Fani & Mawardi, 2022), showed that are valid and practical results as well. Other studies also implement learning model in guided inquiries using Student Worksheet teaching materials on a balance of chemical materials to obtain validity, practicality, and effectiveness, which are very important in the learning process (Kardena & Mawardi, 2021).
Research conducted by Guswita & Mawardi (2021) showed that the Development of a Flipped Classroom Based on Guided Inquiry Learning System on Acid-Base Solutions for XI Class of SMA obtained an average validity result from experts review for content and media, 0.84 and 0.87, respectively. The practicality test from the teachers and students are 89% and 92%, respectively. However, the level of effectiveness had not been tested on learning outcomes. Thus, this study aims to determine the Effectiveness of Flipped Classroom based on Guided Inquiry Learning System on Acid-Base Solutions for XI Class SMA.

Method
This type of research is quasi-experimental research with Non-equivalent Control Group Design. This research was conducted at SMA Negeri 8 Padang. The population in this study was XI class Mipa students who were registered in the even semester of the 2021/2022 academic year. : Pretest for the control class O4 : The final test (posttest) for the control class The sampling is taking by the purposive sampling technique. The sample class used in this study was class of XI MIPA 1 as a control class and class of XI MIPA 2 as an experimental class with the total of sampling were 69 students. The instruments used are pretest and posttest. The type of the instruments used is a multiple choices question consisting of 20 questions with five answer choices with a test for validity, reliability, discrimination index, and difficulty index. The effectiveness of the learning system can be determined through N-gain testing, normality, homogeneity, and hypotheses in the proof. These tests are described as follows:

Normalized Gain (N-Gain)
The level of understanding and mastery of students' concepts related to the material that can be seen through the N-Gain Test. The value of each pretest and posttest value in the sample class is compared as formula 1: (1) The normality test aims to determine whether the sample data is normally distributed or not. The normality test is carried out using the Lilliefors test as Formula 2: (2) The data can be said to be normal if Ltable > Lo and if Ltable < Lo then the data can be said to be not normally distributed.

Homogeneity Test
This test aims to determine whether the sample data has a homogeneous variant or not. The F test is carried out as Formula 3: (3) Information : F : Data frequency S1 2 : The largest variation of learning outcomes data S2 2 : The smallest variation of learning outcomes data The significant level used is 0.05. If the value of Fcount ≤ Ftable then the two groups have homogeneous variance and vice versa.

Hypothesis Test
Hypothesis testing is done by using the t test. If the results of data analysis are obtained on the initial variable and the final variable is at the sig level < 0.05 where tcount> ttable then the hypothesis can be accepted and shows significant results.

Result and Discussion
This research was conducted at SMA Negeri 8 Padang using two classes of XI MIPA samples. This study began with a multiple-item test of validity, reliability, discrimination index, and difficulty index (Latisma, 2011). The data processing of questions is analyzed by using Microsoft Excel. Based on the results, out of 35 questions only 20 questions have been obtained that meet the conditions of validity, reliability, difficulty index, and discrimination index. Each question consists of five answer choices that have been adjusted to the indicators of achievement of competence in acid-base solutions. Students who answer correctly will get a score of 1 with 5 points per each, and students who answer incorrectly will give a score of 0 with 0 point. This question will use as a pretest and posttest for effectiveness analysis.
The effectiveness of a learning system can take a look at the acquisition of learning outcomes. Before starting the lesson, students will take a pretest to determine whether to understand the knowledge. After that, a posttest aims to assess the extent to which students mastered the material after the learning process (Latisma, 2011). The results of the pretest and posttest data analysis are available in Figure 1. Based on Figure 1, there was a significant increase in the pretest-posttest scores in the experimental class compared to the control class. That happened because of the different treatments in both the control and experimental classes. The control class had treatment using a face-to-face learning system or those commonly applied in learning at the school. The experimental class had treatment using a guided inquiry-based flipped classroom learning system that had been written by Guswita & Mawardi (2021).
The flipped classroom is a learning activity in which learning activities in the classroom become activities at home. The flipped classroom has two stages, namely the introduction and concept stage before the class takes place (asynchronous) and the stage related to concept evaluation during the course (synchronous) (Chaeruman, 2013). The guided inquiry model is associated with the process of critical thinking, analysis, and answers independently . According to Hanson (2005), guided inquiry learning consists of five stages that are: (1) orientation, (2) exploration, (3) concept formation, (4) application, and (5) closing.

Figure 2. Flipped Classroom On Guided Inquiry Learning System
Based on Figure 2, Exploration, concept formation, and application are asynchronous for the orientation stage, while the closing stage is part of synchronously. The description of activities of each stage is explained as follows: The first stage is orientation. At the orientation stage, the teacher prepares students to start learning activities. Students looked at orientation video that consists of motivation, apperception, indicators of learning competence, learning objectives, and introductory materials designed by the teacher and uploaded into the homepage of the Edmodo. In the video, learning objectives and motivation can attract students' curiosity regarding the material to be studied (Hanson, 2005;Susanti & Hamama Pitra, 2019). At this stage, students watch the video first independently.
The second stage is exploration and concept formation, while the stage is interrelated. At the exploration stage, students can explore, analyze the model, and collect information related to the model representing the concept. The process is followed by answering key questions that lead students to gain a conceptual understanding tailored to the learning objectives (Hanson, 2005). Out of 34 students divided into 6 study groups, three have been chosen to represent the variation of answers related to the model. An example of one of the models that will use in this study is available in Figure 3.  Figure 3 is a model that illustrates the multirepresentation of chemistry related to the Arrhenius theory of acids. Arrhenius acid is a compound that produces H + ions in water to increase the concentration of H + ions. Based on the model presented in Figure 2, students can observe that HCl can be ionized to form ions (Theodore Brown, 2017). According to Nivaldo, (2019), HCl is a covalent compound and does not contain ions. However, when HCl is dissolved in water, HCl can form positive ions and negative ions. The ions are H + (aq) and Cl -(aq). The H + (aq) ion formed is reactive. There the following reaction in an aqueous solution is formed: Based on the equation for the reaction, the resulting H + ions prove that HCl is acidic according to the Arrhenius theory. The results of the analysis of student answers are available in Table 2.  Based on the student 1, 2, and 3 answers, it can be seen that students 1 and 2 can analyze the model and think critically in answering key questions. Student 1 and student 2 can determine that the HCl in the model can be ionized and be able to write the equation for the reaction. Student 1 and student 2 also identified H + ions from the HCl solution. So that it can guide students in drawing concepts related to the acid, according to Arrhenius. Student 3 can know that HCl ionizes to form H + ions in a solution based on the model presented. However, student 3 was unable to write the reaction equation correctly. Hence, student 3 drew the concept of acid according to Arrhenius only based on the model. In contrast, student 1 and student 2 could draw the concept of the acid theory according to Arrhenius based on the model and write the reaction equation.  Figure 3, students are required to observe the model, the bonds formed, and draw concepts based on critical thinking and analysis that has been done. The reaction between BF3 and NH3 forms Lewis acid-base neutralization. Neutralization is the formation of a coordinating covalent bond between the donor (base) and acceptor (acid). From the reaction between BF3 and NH3, a bond is formed between Nitrogen (N) and Boron (B), creating a coordination covalent bond where Nitrogen will donate its proton and Boron acts as a proton acceptor. Therefore, according to Lewis, an acid is an ionic compound or any molecule that can accept an electron pair in forming a covalent bond. At the same time, a Lewis base is an ionic compound or molecule that can donate an electron pair to create a coordinating covalent bond. So based on the model, NF3 is Lewis base, and BF3 is Lewis acid (James E. Brady, 2012), so the data obtained from students answers are available in Table 3. Based on this answer, student one can draw the concept that Lewis acid is a substance that can accept an electron pair (acceptor), and Lewis base is a substance that can donate an electron pair (donor). Student 2 If NF3 is reacted with BF3, then NH3BF3 will be obtained with the type of bond formed as a covalent bond. Based on these answers, student 2 can draw the concept that acids are electron pair acceptors and bases are electron pair donors. Student 3 Because NF3 has a lone pair of electrons, NF3 acts as a lone pair donor to BF3 as a lone pair acceptor. Thus, a coordinating covalent bond is formed. Based on these answers, student 3 can draw the concept that an acid is a compound that can accept an electron pair or an acceptor, and a base is a compound that can donate an electron pair or a donor.
Based on the results of the comparative analysis of student answers, it can be seen that student 1 and student 3 can correctly analyze the changes that occur in the model where NF3 has one lone electrons pair while BF3 has no lone pair electrons. NF3 donates its electron pair to BF3 and forms a coordinating covalent bond. Student 2, it seems, does not understand the instructions for key questions related to changes in the model and is less specific in answering the bonds formed from the model presented. Based on the analysis of these answers, students 1, 2, and 3 were able to draw concepts related to Lewis acids and bases. Based on the research, each student provides answers and various scores related to the analysis. When students explore the model and think critically in answering key questions, students can find the concepts contained in the model so that students can achieve the learning objectives that have been set.
The next stage is the application. In this stage, identifying concepts that have been obtained, students can strengthen and clarify the concepts acquired in the previous stage by working on questions in the exercises at the application stage. Students can be integrated with other concepts if the concepts applied to the practice questions are successful.
The last stage is closing. In this stage, students conclude the concepts that have been found. In addition, students also provide a protest, feedback, and input. At the same time, the teacher will confirm and deliver reinforcement related to the concepts that students have obtained. The effectiveness of the flipped classroom learning system based on guided inquiry on acid-base solutions, it can be seen by conducting tests such as the following:

Normalized Gain (N-Gain)
The measurement of the N-gain value aims to determine the increase in the understanding of the sample class. N-gain processing is derived from the difference between the post-test and pretest scores obtained by students in both the experimental and control classes. According to Hake (1998), N-gain has three criteria: high criteria with g 0.7, medium criteria with 0.7 > g > 0.3, and low criteria with g 0.3. After carrying out the pretest-posttest, the N-gain results are available in Table 4. Based on Table 4, the average N-gain value for the experimental class is 0.80, and the control class is 0.73. The average value obtained from the experimental and control classes belongs to the high criteria according to the criteria (Hake, 1998). It states that the guided inquiry-based flipped classroom learning system is effective on student learning outcomes. Furthermore, the normality test, homogeneity, and T-test are helpful as a requirement in concluding whether the hypothesis is accepted or not.

Normality Test.
The normality test is to know whether the data that is obtained is normally distributed or not (Sudjana, 2005). The data can be concluded to be normally distributed if the value of Lo < Lt, using the significance level (α) is 0.05. Based on the data processing that has been out, the normality test results are available in Table  5. Based on Table 5, the results were obtained for the experimental class with a value of Lo = 0.141 and a value of Lt = 0.151, while for the control class with a value of Lo = 0.130 and a value of Lt = 0.149. It shows the value of Lo < Lt at the significance level (α) is 0.05. In line with the opinion according to Sudjana (2005) that the distribution of values in the two sample classes as normal.

Homogeneity Test
The homogeneity test processing is available in Table 6.  Table 6 shows that the value of Fcount = 1.24 and Ftable = 1.76, so it can be through that the value of Fcount<Ftable. So that the analysis of the data is obtained that the data are normally distributed and have homogeneous variations.

Hypothesis Test
The last data analysis is to test the hypothesis by using the t-test. T-test can be done if the data from the yields of students' pretest and posttest are normally distributed and homogeneous. Hypothesis testing determines whether the researcher's hypothesis can be accepted or rejected. The results of the t-test data processed using Microsoft Excel that available in Table  7. Based on table 7, the difference in pretest-posttest values shows that the t-count is more significant than the t-table. According to Sudjana (2005), if the value of tcount>ttable, then H0 is rejected. In other words, this value shows the learning outcomes of the experimental class that applies the guided inquiry-based flipped classroom learning system on acid-base solutions are higher than the control class.
The findings of this study are in line with research of Akhmalia et al (2018), which states that the application of learning using flipped classroom on the guided inquiry model in XI Science class can significantly improve learning outcomes in experimental class with an N-gain value of 0, 83 compared to the control class with a value of 0.72. This is because flipped classroom learning with an inquirybased learning model emphasizes the active role of students in finding concepts independently by using LKPD teaching materials and can provide time for students to prepare themselves optimally for class learning. The same result was also obtained by the research of Hidayati et al (2018) conducted at SMA Bandar Lampung, getting an N-gain value (0.84 > 0.70) which stated that the use of an LMS-based blended learning approach with a guided inquiry model was able to improve The concept of students with excellence is to provide students with interest in independent learning because they can access information via the internet anywhere and anytime.
Using FGIL can benefit students because students can learn anytime and anywhere at the asynchronous stage. In addition, by using a learning management system in the learning process, digitalization of education has been carried out by utilizing technological developments to support the learning process. Students can also learn anytime and anywhere at their own pace and with learning strategies (Guswita & Mawardi, 2021). In Edmodo, there are already learning videos and worksheets that using in colorful and attractively designed.
Positive learning outcomes are generated through the solutions that have been taken. The use of the flipped classroom based on guided inquiry learning system in acid-base solutions for class of XI SMA can improve student learning outcomes with a high level of effectiveness category is 0.80.

Conclusion
Based on the research that had been done, the Ngain value for the experimental class was 0.80 and the control class was 0.73 which was included in the high category. In the t-test which was carried out to draw the results of the hypothesis, it was obtained that the value of tcount was greater than ttable with 3.18 and 1.99, respectively. Overall, the results of the study indicate that the use of a flipped classroom based on guided inquiry learning system on acid-base solutions is effective because it improves students learning outcomes.