What are the properties of water that make it so unique? Why are these properties so vital to?
The three most important properties are that it expands on freezing, it is polar, and it has high heat capacity. If water did not expand when frozen (but shrank instead, like almost all metals do), then each winter more ice would form in seas and lakes, sink to the bottom, and then stay frozen through much of summer (the surface water would insulate well, because it has such high heat capacity), and the water left on top would get saltier and saltier, and shallower and shallower — killing off all the life in the sea. Life would not have evolved into land animals, then into humans. Freezing water (from rain) also plays a part in geological weathering processes (because it can widen cracks, split apart rock, etc). Because water is polar, it will dissolve ionic compounds (all kinds of mineral salts), not just in the seas, but also in rain — important in weathering processes in Geology, as well as chemically. Also important in that in life systems it can transport all kinds of dissolved
