The circuit is protected by a ground fault interrupter in the plug. The water in the tank is grounded. The two bare wires correspond to the two pins on the ground fault interrupter plug. If the wire is touched to the water, the ground fault interrupter will disconnect the circuit.

This is what a calorimeter is used for simpler ex, to measure calories in food.

The answer is water molecules are split.cellular respiration and photosynthesis are complement  reactions to each other. these are reverse reactions. in cellular respiration glucose and oxygen yield water and carbon dioxide. so, when respiration begins,  glucose molecules are split. in the opposite reaction - in photosynthesis, carbon dioxide and water yield glucose and oxygen. thus,  when respiration begins, water molecules are split.