There's always a chance of a difference in potential between a neutral (which is a current-carrying conductor) and the ground. Remember that the ground is generally either steel conduit or flex, which doesn't conduct electricity as well as copper. A volt or two difference between them is certainly possible but doesn't cause any harm.
Now if the hot conductor is still connected and the neutral causes a spark when it touches ground, then of course it will. The loose neutral is seeking a completed circuit and <can> do this via a grounding conductor or conduit.
