Water Freezes Differently on Positively and Negatively Charged Surfaces of Pyroelectric Materials

Freezing Supercool Water Under equilibrium conditions, water will freeze at 0°C, but, under certain conditions, it can be kept in a supercooled liquid form below this temperature. Ehre et al. (p. 672 ) present a careful and detailed study of the freezing of water drops on both positively and negatively charged pyroelectric surfaces using a combination of optical microscopy and x-ray diffraction: Supercooled water froze at different temperatures, depending on the charge of the substrate with the initial freezing occurring at the liquid-substrate interface on a positively charged substrate and at the air-water interface on a negatively charged substrate. Thus, freezing could be induced upon heating when the substrate charge also changed from negative to positive.