Well, it goes like this. Let's say that you have two identical containers having identical amounts of water- one at (say) 20 deg C and the other at 90 deg C. Keep both these containers in a room, where the ambiant temperature is (say) -20 deg C. What will happen is that the hotter water container will have a faster rate of cooling because of a greater temperature difference (110 deg C in this case) between the atmosphere and the water surface. This rate of cooling is lesser for the 20 deg C container. Now lets say that both these containers reach the stage of water at 0 deg C and begin converting to ice at 0 deg C. It's obvious that hereon in the times of freezing (to any temperature) will be the same. Remember that the rate of cooling is directly proportional to the temperature difference between the system and the surroundings. The hotter vessel will have, an initial rate of cooling which is faster than the less-hot vessel. But as the temperature declines, so does the rate of cooling. Let me give an analogy. Take the sprinters in the 800m events. You have the sprinter in the innermost lane start from a distance behind the outer most runner. This stagger compensates for the lesser distance the innermost sprinter has to run. At the start of the race, you will find that the innermost runner 'appears' to be catching on to the others. This is because of the lesser distance. But at the finish line, they all are pretty much about the same formation. Compare the short distance to the faster initial rate of cooling...the hotter body gains in on the colder body quicker, but at the temperature goes decreasing (or the race advances) that advantage disappears, because both vessels have to cope with the same temperature difference and hence cool identically. So when this temperature is reached (say, about 5 deg C) the rates of cooling will be identical, and thereon both water bodies will freeze identically. Note: This holds only for water samples which are pure. The cooling curves and the freezing patterns will change if there are non-volatile impurities in either water sample.

It's true. The hot water will cool faster than the room temperature water, but that has nothing to do with it. By the time the hot water hits room temperature, it will have the same rate of cooling as the the original room temperature water. Howver, by that time the room temperature water will have cooled more. If that was the only factor, the hot water would always be behind. That's not the whole story, though. If the water is hot enough, there will be a significant amount of evaporation. The smaller amount of water will cool more quickly and might form ice faster. So while the same initial volume of hotter water might freeze faster, you'll end up with less ice in the end.

yes it does, much faster. i poured an ice tray with hot water and one with cold water and after a couple of hours the one that had hot water in it was completly frozen and the one that has cold water in was still mushy! weid eh?! try it out!

There are at least five effects that contribute to hot water freezing faster. 1) Evaporation. Some of the hot water evaporates, leaving less water left to freeze. 2) Supercooling. Hot water is more likely to get supercooled below the freezing point. The hotter water near the walls of the hot container keeps the cool water away from nucleation points where the freezing process begins. Supercooled water then freezes faster. 3) Convection. Once the cold water freezes on the surface, it makes an insulating layer against further freezing. But as the hot water cools it sinks setting up currents which stir the liquid as it begins to freeze, cooling it quicker. 4) Dissolved Gases. Dissolved gases lower the freezing point below zero. Heating water drives out the dissolved gases so it freezes at a higher temperature than the cold water. 5) Conduction. When placing a object in a freezer, the hot container will melt ice under it, making a better contact with the cold surface than the insulating layer of ice under the cold container. http://hepth.hanyang.ac.kr/~sjs/physics/hot_water.html

The "freezing" happens when a body at a temperature elevated from its surroundings looses heat. This is a natural phenomenon, as heat flows from a body of high temp to a body of low temp. (Much like how water at a higher elevation flows down to a lower level) But the rate at which heat flows from the source (Body at high Temp) to the sink (Body at Low Temp) depends on the temperature difference. The greater the difference, the greater the flow. Here flow means the amount of heat (say calories) that flow out per second. Coming back to the case, a tray of hot water dissipates more heat to its surroundings than a tray of cold water. This is solely by virtue of the potential difference between the water trays and the surroundings. That means, if two trays full of water (One at 60 deg and other at room temperature) are kept in a same refrigerator for the same time period, then although the tray of hot water looses more heat per sec, it is the cold water that gets frozen faster (simply because it does not have to stay as long as the hot water tray to dissipate heat)

Yes, hot water freezes faster - because higher temperatures trap gasses in the water, there is more surface area within the water to convect heat away.