In a German out-of-school laboratory, 293 medium-achieving 10th-grade students participated in a lesson unit about gene technology. They were divided into two groups (I-1, I-2), both of which followed the same hands-on lesson procedure. Students within I-2 were additionally confronted with alternative conceptions to central issues of the specific…

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 7,441 German senior high school students were asked to work on 154 test items…