Mental models of atomic structure concepts of 11th grade chemistry students

Research design

The study design followed the study design has been done by Sunyono & Yulianti (2015), that is qualitative with observation. The design of this study includes observational investigation, interviews, and tests of mental models filled out by the students. Observations aim to obtain data on the use of learning during this high school chemistry teacher in Lampung and data of students' mental models. Test of mental models conducted to reveal the reasoning abilities, interpretation, and representation of students' abilities. The ability is further defined as a mental model. Interviews were conducted to reveal the students' difficulties in understanding, reasoning, interpret, and represent chemical phenomena.

Participants

Participants of this study were taken from three districts/cities were selected randomly from all regions in Lampung province of Indonesia. The next randomly selected three high schools as a sample. Sampling the school used to get the respondent students with different backgrounds. Furthermore, each of the selected schools was taken randomly one class 11, in order to obtain three class 11 as a sample of a study with the overall number of students as many as 89 people. The three classes each derived from (1) senior high school in the provincial capital (School A: students who were in the neighborhood of employees and vendors) with the number of students as many as 30 people; (2) senior high schools near the provincial capital (School B: students in a farming environment) with the number of students as many as 29 people; and (3) senior high school far from the provincial capital (School C: students who are in the company's industrial/agro-industry) with the number of students as many as 30 people. Students from each school were given a questionnaire about learning undertaken by teachers, then given tests of mental models, further interviews after the student has completed the exam.

Instrument and Procedure

Selection of participants (high school students) as the sample has been done, then performed a survey/observation of these students. Surveying/Observation is assisted by a chemistry teacher from each school to be sampled, then students are asked to complete the observation sheet for 30 minutes. To ensure greater uniformity in the administration of the survey in all classes, teachers are asked not to provide opportunities for additional information beyond what is written in the survey. Investigative observations sheets include 10 items that must be answered students' questions related to the implementation of the study conducted by the teacher.
Tests of mental models used in the form of shaped test essay were adapted from a model developed by Park & Light (2009). The instruments of test of the mental model developed by Park & Light (2009) emphasize more on conceptual definitions ranging from atomic definitions, atomic structure explanations, identification of atomic parts, explanations of orbitals, orbital forms, and the number of electrons in each orbitals . In this study, Park & Light questions were modified starting from the understanding of atomic structure in a process of chemical and physical change, representation of images of atomic structures (protons, electrons, and neutrons) of an atom based on experimental results from Rutherford, Thomson, Goldstein , and Chadwick. The question continues on the description of the Bohr atom model for a given atom complete with its energy level. The mental model of students as measured in this study is a conceptual mental model that appears in response to questions in the diagnostic tests on the topic of atomic structure (especially the nuclear model of the atom, Rutherford, Bohr, and wave mechanics). The instrument used to determine the appearance of students' mental models is a form of essay test, hereinafter called the Test of Atomic Structure Model (TASM). Question on diagnostic tests to see the emergence of mental models of the students in understanding the topic of atomic structure. Instruments of tests of mental models are validated in advance by the relevant experts, before being used in research. To validate the instrument used three experts in the field of chemistry and two experts in the field of psychology. Expert validation results show that 100% validators provide high assessment of the mental model test questions that have been made, so it can be said that the mental meodel test instrument has high content validity and can be used for research. The mental model test instrument consists of three TASM questions (see below).

TASM-02.

a. Based on the experimental results of Rutherford, Thomson, Goldstein, and Chadwick. Give an explanation of the structure of atoms and draw an atomic model complete with its parts (protons, electrons, and neutrons) from the and !

b. Write the element with the symbol for each atom notation as described below.

TASM-03. Based on the Bohr model of the atom, the number of electrons for each energy level follows the equation 2 n². Draw a picture the Bohr atomic model based on the results of your imagination of fluor atoms (Z = 9) and sodium atom (Z = 11), complete with energy levels according to Bohr!

The interview guide was developed in this study is a semi-structured interview guide. The interview guidelines were developed by adapting of the interview guides developed by Park (2006), in the form of questions that ask students to provide an explanation for the student answers on tests of mental models. Interviews with students conducted to find out more about the answers to the students and the difficulties that arise in interpreting the phenomenon of a molecul ar level (sub-micro). Before being used in data collection, interview guides that have been prepared beforehand validated by relevant experts. Interview guides were validated by two psychologists and the results of all validators agreed that the interview guidelines could be used for the study. Interview guidelines of expert validation results are described in Table 1 below.
Interviews were conducted after scoring on a mental model test.. Interviews were conducted with three students were selected from the whole sample (89 students). Three students were randomly selected from three different schools and each school was chosen by one person as a respondent. The students selected for the interview were the students who scored highest on a mental model test. The consideration is students who have low test scores, ie students with mental models categorized "bad". Interviews with students were conducted to find out more about the responses of the students and the difficulties that arise in the creative problem-solving.

Table 1. Interview Protocol

Category	Questions
Definition of Atom	What is an atom?
Previous Knowledge	Have you studied the structure of atom before taking this course? Are you able to identify any changes that occur in each process shown by the question No.1 (TASM-01)? How is your analogy in answering these questions?
General Knowledge	Please see the question on TASM-02 Please explain or describe the structure of an atom. Please draw an atom.(you may use any atom as an example) Tell me about the parts of your drawing of the atom. Please explain more about your drawing. Does your drawing help you to understand the structure of an atom? Do you know what is meant by a “model” in science? Can you give me a model of an atom? Tell me about your understanding of the atomic model of an atom. Do those models help you to understand the atomic structure? Can you explain about it?

Data Analysis

Data obtained from the results of diagnostic tests and interviews were then analyzed through transcription and categorization, so initial mental models of students could be identified and common general difficulties that occur when dealing with the external representation of the submicroscopic level, especially in the problem solving of the atom model concept. Students' mental models were analyzed by interpreting the answers of students on each question of the test mental models. If the student answers to the questions of the test mental models vary widely, so do the answers grouping students into several types according to a similarity of answers. Types of student answers categorized (sorted) in accordance with the responses of the students starting from no attempts (no answer) to the most appropriate answer. Furthermore, the number of students in each type is expressed as a percentage. This is done by adapting the research conducted by Wang (2007) and Park (2006), where to know the features of an individual's mental model of the student, Wang (2007) and Park (2006) using coding to the explanation of verbal and nonverbal students, and the encoding using the types of student answers as explanations of nonverbal representation of students. Encoding mental model test data is done by giving a score to each student answers according to the type of student answers. Mechanical scoring is done by using a rubric, namely by assessing the students' answers on tests with descriptions use the label to determine the level of achievement solve the problem (Sunyono, Yuanita & Ibrahim, 2015). The level of achievement in problem solving are then categorized as a mental model of "very bad/unformed" (where a score = 1), "bad" (score = 2), "medium" or "moderate" (score = 3), "good" (score = 4), and "excellent" (score = 5).