Water freezes when it reaches certain conditions of pressure and temperature. At the temperature at the surface of the Earth, the temperature is 0 degrees C (or 32 degrees F). Water does not freeze unless its temperature drops to that point - ever.

When you put water into a freezer, the cold temperatures in the freezer lower the temperature of the water until it reaches the freezing point, at which point it freezes. The warmer the water is to begin with, the farther it has to go before it can freeze.

Cold water would freeze faster than hot water, since one would have to remove less heat from it. One way to tell is to fill two cups: one with hot water and the other with cold water and keep them in the freezer. Keep checking every hour if the water in the two cups has turned solid or not.

You could do an experiment to find out if hot or cold water freezes faster. I'll predict that cold water will freeze faster, because it doesn't have to cool down as much before it freezes. What do you predict?