Analysis of Students’ Comprehension and Misconception towards the Topic of Salt Solubility

This study aimed to analyze students’ comprehension and misconception towards the topic of salt solubility both on the level of microscopic representation and understanding. This study utilized essay diagnostic test as instruments and interviews based on a case study of 10 students in grade 11 at senior high school in Bogor who were given 8 questions regarding salt solubility. The results showed that there was a misconception, 40% of the students misled in drawing microscopically the system of salt and sugar solubility and 50% of the students incorrectly drew the system due to the absence of interaction between salt particle and water, while 10% of the students sketched correctly though it is difficult to notice the result of salt ionization on the solvent. Moreover, 80% of the students were unable to find a link between the alteration system of solvent equilibrium caused by additional salt with various solvents on the macroscopic concept of an insoluble salt equilibrium system and the effect of adding similar ions on the equilibrium system.


INTRODUCTION
Chemistry is a branch of discipline that studies materials in the universe that include changes in matter, interactions and energy related or caused by natural changes (Schaum, 2017;Oxtoby, 2001;Brady, 2000;Flowers, 2015;Megna, 2016). Through namely the real macroscopic level that is visible to the eye, submicroscopic level which is real but cannot be seen directly without a microscope, and symbolic level that contains formulas, chemical equations, graphs and many others.
Learning chemistry, therefore, is necessarily required to students.
The learning process itself must be supported by a method that integrates chemistry with the occurrence in the natural environment and the daily lives of the students (Jones et al., 2007;Jones et al., 2015;Uce, Ceyhan, 2019;Childs, 2015). By doing so, students can construct the knowledge not just limited to understanding the concept but also developing the competence as a whole. (Rahmawati dkk 2017;Taber 2002). Chemistry is not an easy subject to teach and learn both in middle and high level of education (Treagust, 2000;Ozmen & Yildirim, 2005). This is because the curriculum in Indonesia is overloaded; for instance, chemical subject is less associated with daily life.
As a result, chemistry becomes abstract and difficult to comprehend. Students tend to memorize chemical concepts in the description of words without being able to explain why and how the process of a substance experiences a reaction (Rahmawati, 2013;Sanchez, 2017). can be seen in Table 1.

Concept of solubility in solvent system
According to the students' answers of the 1 st question, it was found that there  Based on the answer of type II in Figure 2, there was an interaction between salt particle and water particle.
It can be seen from the circle-draw of  figure   3.

Figure 3. Distribution of H 2 O and NaCl particles
Based on the answer of type III in Figure 3, it can be seen the criss-

Reaction of salt on the water
According to the answer of the 2 nd question, it was found out that there are 3 types of students' answers in formulating the ion reaction of salt within water (symbolic).
Answer type I (20%): NaCl + H 2 O salt water (contains Na + dan Cl -) Based on the answer, students seem to be confused in writing the result product from ionization of NaCl within water.

NaCl + H 2 O NaOH + HCl
Based on the answer, students remain misconceptualized the ionization reaction of NaCl. The correct answer is when the NaCl is dissolved within water, there is an ionization process to become ion Na+ and Cl- (Buthelezi, 2008 NaCl Na + + Cl -40% Saturated solvent, unsaturated and oversaturated 5 Students could connect macroscopic images of the distribution of salt particles in water to saturated, unsaturated and over-saturated solutions but they couldn't connect the changes in the system's equilibrium system due to the addition of salts to the types of solutions (saturated, unsaturated and saturated solutions)

80%
Students could connect submicroscopic images of the distribution of salt particles in water to saturated, unsaturated and oversaturated solutions and they could connect changes in the equilibrium system of solutions due to the addition of salts to the types of solutions (saturated, unsaturated and saturated solutions) 20% 7 Students could match correctly the definitions with the terms of solubility 80% Students could match incorrectly the definitions with the terms of solubility

20%
The system of salt equilibrium that is difficult to dissolve 8 Students were confused in connecting submicroscopic images with the equilibrium system of AgCl solvent 100% Students incorrectly wrote AgCl ionization reaction in AgCl Ag + + Cl -

60%
Students were mistaken in terms of the concept of equilibrium in the AgCl solution system "It is said to be balanced if it has the same amount or period so that it has the same concentration."

40%
The effect of similar ions in the salt balance system 4 Students were incorrect in predicting the direction of the equilibrium 30% 70%  Students were incorrect in predicting the direction of the equilibrium shift, and did not recognize the effect of shifting the equilibrium towards the product of the salt solubility according to the of Le Chattelier  Most of students could predict equilibrium shifts when there was an addition of similar ions in solution, but cannot connect the effect of shifting equilibrium toward the product to salt solubility Jurnal Penelitian dan Pembelajaran IPA Izzati & Rochmah Vol. 6, No. 1, 2020, p. 152-165 161 States that AgCl has complex ions that can cause difficult to dissolve (Silberberg, 2012).