Pure water will always freeze at 0 C. Keeping it moving just cause friction within the molecules that causes the water to heat up. Friction does that.
Salt (and for the most part any dissolvable substance) in water interacts with water molecules, not allowing them to bind with each other when they slow down thus lowering the temperature at which point the solution freezes, because the salt molecules must slow down as well. I believe the lowest possible temp with salt water is 21 C.
And I hated Chemistry.
If you want something cool to look up, do a search for Absolute Zero.
