The increasing availability of augmented reality (AR), virtual reality (VR), and other information and communication technologies offers new and exciting opportunities for chemistry education. To ensure their effective implementation in schools, evaluating their efficiency is essential before widespread adoption. This study investigates the cognitive load associated with different representation formats – molecular models in VR, AR, on a computer screen, and physical models – during the solution of chemical representation tasks. Knowledge test, subjective and objective physiological indicators, such as heart rate, were used to assess students’ cognitive load. Here, the results of a study involving 89 students in 5 lower secondary schools are presented. Tests of 40 students were analyzed, and the results indicate that augmented reality may be most effective for learning spatial literacy topics.