1. Non-toxic wood materials and metal parts, clock

2. Lemon-powered clocks work by using the process of electrolysis. The lemon juice is an acidic electrolyte, which is then connected in a circuit through a metal electrode. There must be two different metals present to produce an electric charge; zinc and copper are common. Otherwise, an outside electric source would have to be present to induce electrolysis. The two metals produce the current necessary to charge the electrolytes, thus allowing the process of electrolysis (separation) to occur and electricity to flow enough to power a clock.