4C is the temperature at which H20 is most dense, so it makes sense use that temp when defining a mass in terms of a volume. http://en.wikipedia.org/wiki/Prope

4C is the temperature at which H20 is most dense, so it makes sense use that temp when defining a mass in terms of a volume. http://en.wikipedia.org/wiki/Properties_of_water#Density_of_water_and_ice http://en.wikipedia.org/wiki/Properties_of_water#Density_of_...