STOICHIOMETRIC PROBLEM-SOLVING IN HIGH-SCHOOL CHEMISTRY

The purpose of this descriptive study was to create and test questions on stoichiometry with number ratios for quick mental calculations and to identify students' problem-solving strategies. The present study was a component of a more comprehensive investigation in which 7441 German senior high school students were asked to work on 154 test items from 10 different topics. A random sample of 4181 out of the 7441 students completed the paper-and-pencil tests on stoichiometry. Additionally, discussions with students about how they solved the test items were videotaped. The study uncovered five strategies students used to solve the test items on stoichiometry. With some test items the possibility that students came to the correct result, although they had used incorrect solving strategies, could not be excluded. However, it was possible to improve these test items. This indicates that students' successful solving strategies have to be known in order to decide whether a test item is mature or not. It was noted that most students successfully applied problem-solving strategies that were not presented by chemistry textbooks. The test items developed in the study and the problem-solving strategies observed may be used to introduce students to stoichiometric calculations.