The publicly available free computer program, "SimChemistry," was used as an active learning tool in the chemical engineering curriculum at the University College of Boras, Sweden. The activity involved students writing their own simulation programs on topics in the area of molecular structure and interactions. Evaluation of the learning experience was done using interviews and by comparing learning outcomes with previous teachings of the topics. Overall, the outcome was interactively engaging group work, high quality construction of simulations, and a much better ability to explain molecular-level chemical concepts and their relations. An interesting perception that emerged during the interviews was that many of the students were unable to explicitly describe the improvement in learning that they had experienced. However, they did recognize that learning had occurred, and all firmly and positively recommended that the initiative be continued for subsequent courses. (Contains 1 table and 1 figure.)