  Fundamental concepts of thermodynamics rely on abstract physical quantities
such as energy, heat and entropy, which play an important role in the process
of interpreting thermal phenomena and statistical mechanics. However, these
quantities are not covered by human (visual) perception and thus, an intuitive
understanding often is lacking. Today immersive technologies like head-mounted
displays of the newest generation, especially HoloLens, allow for high quality
augmented reality learning experiences, which can overcome this perception gap
and simultaneously avoid a split attention effect. In a mixed reality (MR)
scenario as presented in this paper---which we call a holo.lab---human
perception can be extended to the thermal regime by presenting false-color
representations of the temperature of objects as a virtual augmentation
directly on the real object itself in real-time. Direct feedback to
experimental actions of the users in form of different representations allows
for immediate comparison to theoretical principles and predictions and
therefore is supposed to intensify the theory-experiment interactions and to
increase the conceptual understanding. We tested this technology for an
experiment on thermal conduction of metals in the framework of undergraduate
laboratories. A pilot study with treatment and control groups (N = 59) showed a
small positive effect of MR on students' performance measured with a
standardized concept test for thermodynamics, indicating an improvement of the
understanding of the underlying physical concepts.
