Abstract
<p>The representation of electronic excited states as spatially "higher" than ground states on potential energy diagrams is so ubiquitous in chemical education that its metaphorical nature is rarely examined. This paper presents a qualitative discourse analysis of twelve undergraduate chemistry textbooks to investigate how the vertical metaphor is linguistically and visually instantiated—and critically, whether textbooks exhibit any awareness of its representational nature. We systematically code for metalinguistic framing (instances where authors acknowledge the diagrammatic convention) alongside conventional spatial metaphors ("high energy," "promotion," "energy landscapes"). Our findings reveal a striking asymmetry: while vertical spatial metaphors occur with high frequency (mean 28.4 instances per textbook), explicit justification for why energy is plotted vertically is virtually absent (zero instances across the entire corpus). Integrating Conceptual Metaphor Theory with Dual-Process cognition (System 1/System 2), we argue that this pedagogical silence does not merely reflect convention but actively reinforces the metaphor's operational opacity—rendering it a powerful cognitive artifact processed intuitively rather than a consciously evaluated representational choice. We conclude that the vertical diagram is not a failure of accuracy but a triumph of cognitive design, yet one whose metaphorical nature should be explicitly taught to foster greater representational literacy in chemistry students. This study contributes to foundational debates in chemistry concerning the nature of scientific representation, the relationship between quantum theory and its visualization, and the role of pedagogical practices in shaping disciplinary epistemology.Keywords: Conceptual metaphor, quantum chemistry, textbook analysis, energy diagrams, embodied cognition, philosophy of chemistry, dual-process theory, representational literacy, scientific representation, discourse analysis.</p>