Attitudes toward learning (ATL) have been shown to influence students' learning outcomes. However, there is a lack of knowledge about the ways in which the interaction between ATL, the learning situation, and the level of students' prior knowledge influence affective reactions and conceptual change. In this study, a simulation of acid-base titrations was examined to assess the impact of instruction format, level of prior knowledge and students' ATL on university-level students, with respect to flow experiences (Csikszentmihalyi, 1990) and perceived conceptual change. Results show that the use of guiding instructions was correlated with a perceived conceptual change and high levels of "Challenge," "Enjoyment," and "Concentration," but low sense of control during the exercise. Students who used the open instructions scored highly on the "Control flow" component, but their perceived learning score was lower than that for the students who used the guiding instructions. In neither case did students' ATL or their pre-test results contribute strongly to students' flow experiences or their perceived learning in the two different learning situations.