Lecturing is an important aspect of the culture of science education. Perhaps because of the negative associations constructivist educators make with lecturing, little research has been done concerning the generally invisible aspects of the (embodied, lived) "work" that is required. Traditional research on science lectures focuses on ideas and (mental) concepts that somehow are "gotten across"; and it is interested in identifying verbal content and visual representations science teachers provide. The purpose of this study is to explicitly describe and theorize the living work of lecturing that produces in a societal arena everything from which students can learn. We use two case studies from the chemistry lectures in a tenth-grade Singapore classroom to exemplify the central role of the performative aspects of lecturing. We articulate and exemplify assertions that (a) corporeal performances differentiate and coordinate the contents of lecturing with its pitch, rhythm, and speech volume, and thereby orient students to specific discourse features of chemistry; and (b) corporeal performances differentiate and coordinate layers of talk with prosody, gestures, and body orientation, and thereby make analogies available to students. We conclude that what is visible in lectures (e.g., scientific discourse, analogies) is always the outcome of the (generally unattended to) corporeal labor including gestures, body orientation, and prosodic features (e.g., shifts in pitch) and that this outcome | labor pair constitutes an appropriate unit of understanding lecturing as societal phenomenon.