(1) When the electric fan works, it consumes electric energy to generate mechanical energy, so it converts electric energy into mechanical energy.

(2) When the electric water heater works, it consumes electric energy, generates heat energy, and converts the electric energy into internal energy;

(3) When the rice cooker works, it consumes electric energy, generates heat energy, and converts the electric energy into internal energy;

(4) When the soldering iron works, it consumes electric energy, generates heat energy, and converts the electric energy into internal energy;

(5) When the fluorescent lamp works, it consumes electric energy and produces light energy, so it is a process of converting electric energy into light energy;

So the answer is: (1) mechanical energy; (2) internal energy; (3) internal energy; (4) internal energy; (5) light energy;