Like water expanding as it freezes?
That would allow for faster freezing of the hot water also, as the more and faster it expands when actually achiving the frozen state, the more surface area is presented faster which exponenitally speeds up convection, and as such, the rate of freezing.
The volume expansion is due to absorption of air. The water molecules proper still contract with cold, but they pull in and trap air volume kind of like a magnet pulls iron filings. (also why pipes burst when they freeze)
Random relevant note of amusement:
The 'crack' ice cubes do when put in a drink is a result of the trapped internal air trying to expand (air expands and contracts with temperature too) to a molecular spacing (for want of a better word) equal to that of the temperature of the liquid they are dropped in, yet the frozen water 'shell' portion of the cube restricts its expansion and offers no alternate escape/relief for the building pressure.
Simultaniously the shell also wants to contract as it warms, (molecules of water closing upon each other as they release air), so there's a flash shrinking very early on when dropped into the glass of liquid. The air that can't get out fighting against the shell fighting to contract
This ends up making the 'crack' as the pressure of the internal air exceeds the strength of the frozen exterior and the exterior tries to crush down on an uncrushable (for the mechanics involved) core.
Basically it bursts from the inside out and makes a sound at the moment of failure.
I can use the cash.
