Energy salt water 2°

Needed: aluminium can, a thin copper plate, two spacers of rubber, cd rom motor recovered from the pc internal, 1 liter of water with 3-4 tablespoons of salt for foods. The duration of the motor rotation is about 7-8 minutes. When the salt water depletes its energy, it must be filled with new water and salt, or the salt water discharge can be loaded with an external battery of 1.5 volts.
* The success of this experiment is necessary to have an motor that has a low power consumption 15-20 mA max. and a voltage of 2.3 volts, "motor cd rom". The use of motors for toys are not suitable for this type of experiment.
** The copper foil can not be replaced with other metals.