Cryogenic materials, mainly liquefied and solidified gases, are probably the most fascinating materials to use for demonstrating chemical reactions to introductory college students. A popular series of articles (Blachley 1997; Coppola et al. 1994; Haub 2001; Hughes and Haworth 1992; Stamm and Franz 1992) has been published presenting very effective and attractive demonstrations using liquefied gases. The authors describe two versions of a straightforward experiment that illustrates the concepts of energy/heat flow and conversion of heat to mechanical work. It uses a water fountain powered by the expansion of liquid nitrogen or dry-ice.