Various features of scientific discourse have been characterized in the science education literature, and challenges students face in appropriating these features have been explored. Using the framework of conceptual metaphor, this paper sought to identify explicit and implicit metaphors in pedagogical texts dealing with the concept of entropy and the second law of thermodynamics, an abstract and challenging domain for learners. Three university-level textbooks were analyzed from a conceptual metaphor perspective, and a range of explicit and implicit metaphors were identified. Explicit metaphors identified include entropy as disorder, thermodynamics processes as movements along a path, and energetic exchange as financial transactions among others. Implicit metaphors include application and elaboration of the generic Location Event Structure metaphor, application of the Object Event Structure metaphor, and others. The similarities and differences between explicit and implicit metaphors found in the textbooks are also described. Two key pedagogical implications are discussed: that the selection of explicit instructional metaphors can be guided by consistency with implicit metaphors; and that the range of implicit metaphors found in pedagogical texts implies that a multiple instructional metaphor strategy is warranted. The depth of the phenomenon of conceptual metaphor and its implications for future research are also discussed. (Contains 2 tables and 2 footnotes.)