Just a quick note on freezing water on a sheet of ice.
 
Depending on how hot the water is, it is very possible for hot water to freeze
faster than cold water.  To help explain my theory, I'll use an example of ice
water.
 
Take a glass of lukewarm water, and drop ice cubes in it.  The water will get
colder.  As I'm sure most of you can figure out, the fact that ice is cold
helps the water to get colder.  The other part of the heat transfer has to do
with the melted ice.  When ice melts, it becomes 32 degree farenheit water.
 The mixing of the newly melted ice with the hot water lowers the temperature
much faster than if the ice had not melted.  This might explain why hot water
would melt faster than cold water...
 
 
                                Just a thought...
 
                                        Dustin