Identifying students' misconceptions in writing balanced equations for dissolving ionic compounds in water and using multiple-choice questions at the symbolic and particulate levels to confront these misconceptions /

Abstract

Students who harbor misconceptions often find chemistry difficult to understand. To improve teaching about the dissolving process, first semester introductory chemistry students were asked to complete a free-response questionnaire on writing balanced equations for dissolving ionic compounds in water. To corroborate errors and misconceptions identified from students' generated balanced equations, another sample of students participated in semi-structured interviews where they were asked to explain their thought processes involved in writing the balanced equations for the dissolving ionic compounds dissolving in water. Misconceptions of the dissolving process were identified and described in detail. The most popular misconception was that water chemically reacts with an ionic compound through double displacement to form a metal oxide and an acid. The second popular misconception was that an ionic compound dissolves as neutral atoms or molecules. The third popular misconception was that students confused subscripts and coefficients.

Another sample of introductory chemistry students were assessed on the dissolving process using the three popular misconceptions as three of the four choices in multiple-choice questions at the symbolic- and particulate-level. The symbolic-level questions involved symbolic balanced equations and the particulate-level questions involved dynamic animations or static pictures of the same four choices. Students' responses to these questions were discussed in terms of four variables---Answer (the correct answer and three misconceptions), Representation (symbolic or particulate questions), Visualization (static or animated pictures), and Representation Order (symbolic questions before or after the particulate questions).

The same test instrument was used on the same student sample to assess how two types of subscripts affected students understanding of dissolving ionic compounds in water. Two of the ionic compounds had monatomic subscripts (MgCl2, Ag2SO4) and two did not (NaBr, KNO 3). Two had polyatomic subscripts (KNO3, K2SO 4) and two did not (NaBr, MgC12). Students' responses to these questions were also discussed in terms of four variables---Answer (the four choices), Representation (symbolic or particulate questions), Monatomic subscripts, and Polyatomic subscripts. The subscript misconception was more popular for symbolic questions compared to particulate questions, and the correct answer was less popular for particulate and symbolic questions when the question contained a monatomic subscript.