As every schoolchild knows, water freezes at 0oC. Or perhaps not. It has been known for centuries that pure water, in the absence of any nucleating surface, can remain in a supercooled liquid state down to temperatures as low as -40oC. Now, researchers in Israel have discovered that supercooled water itself will freeze at different temperatures depending on whether it is in contact with a positively or negatively charged surface. Ice crystals © Thinkstock Images For more than 150 years it has been known that electrical fields can affect the freezing point of supercooled water. However, it has been difficult to study...