Abstract: In the context of global efforts toward carbon neutrality and peak carbon emissions, developing alternative energy solutions and improving energy efficiency have become critical priorities. Phase change materials (PCMs) show significant promise in addressing these challenges. This article explores the fundamental chemistry behind reusable hand warmers through the “hot ice” experiment, demonstrating how crystallization of supersaturated sodium acetate solution releases latent heat. Beyond its visual appeal, this experiment serves as an engaging introduction to thermal energy storage concepts. We draw parallels between electrical energy storage in batteries and thermal energy storage using PCMs, presenting several practical applications that highlight the potential of this technology for sustainable energy solutions.

Key words: Saturated solution, Supersaturated solution, Sodium acetate, Hot ice experiment, Phase change, Phase change energy storage materials