Students attending object-oriented analysis and design (OOAD) courses typically encounter difficulties transitioning from requirements analysis to logical design and then to physical design. Concept maps have been widely used in studies of user learning. The study reported here, based on the relationship of concept maps to learning theory and semantic memory, suggests that integrating OOAD instruction with concept maps might help learners understand these transitions more clearly. An empirical experiment, involving two treatments based on concept maps and conventional instruction, was conducted to examine the relevance of concept map-based instruction for an effective understanding of phase transitions. The results indicate that compared with conventional instruction, concept map-based instruction is more efficient in improving learner understanding because of greater learner engagement and because of concept maps' properties when they are used as an information medium. This study can aid instructors in realizing the difficulties in learning phase transitions and motivate researchers to develop more effective learning instructions.