-ΔH(H2O2(vap))×1000/Tboil, where S 0 (H2O2(g)) -absolute standard entropy of hydrogen peroxide, 232.95 J mol -1 K - 1 . ΔH(H2O2(vap)) -enthalpy of hydrogen peroxide evapora on, 48.5 kJ mol -1 K -1 . Tboil -hydrogen peroxide boiling point, 423 K. The game implements a drag-and-drop interface. Images of chemicals represent specific compounds and elements. A player selects and drag-and-drops a selected number of chemicals into the area of the screen that represents the reactor and receiver (Figure ). Drag-and-dropping an image of a chemical into the reactor or receiver results in the appearance of a symbolic label that represents this reactant or product on the le or right side of the reac on equa on, respec vely. A player may track the evolu on of upon reac on the reac on equa on by opening the lab book at any me by double-clicking its image (Figure ). One of the educa onal objec ves of hiding the reac on equa on in the lab book, is to train players' short-term memory -to complete levels faster players need to memorize the number and type of chemicals that are contained in the reactor and receiver.