How to make a yes/no coin in just 10 minutes

Facing a tough decision and can’t make up your mind? We recommend making your own yes/no coin – it’ll only take 10 minutes!
Reagents and equipment: 1 copper disc, 5% sodium chloride (table salt) solution, 2 beakers, 2 small tea candles, an aluminum container, a battery holder with four AA batteries, 2 crocodile clip wires, tongs, a wooden stick, hot water, paper towels.
Use one candle to melt the other in the aluminum container. When the second candle has melted completely, use the tongs to immerse the copper disc in the liquid wax for a few seconds, creating a wax coating. When the coating solidifies, use the wooden stick to scratch the words “yes” and “no” in the wax. Connect the blank to the positive terminal of the battery holder via a crocodile clip wire and immerse it in the 5% sodium chloride (table salt) solution. To close the circuit, place the wire connected to the negative terminal of the battery holder in the solution. Observe as gas is released and a precipitate forms. Let stand for 10 minutes. To remove the leftover wax, immerse your newly-minted “coin” in hot water for 2 minutes, then wipe it clean with a paper towel – your words have been engraved on its surface.
The constant electric current in the electrolyte solution sparks a process known as electrolysis. Electrolysis allows us to obtain a multitude of metals and gases, produce protective coatings, and create chemical etchings.
In this case, electrolysis initiates three processes in our system. On the positively-charged wire (the anode), the copper and the iron crocodile clip dissolve. Since the copper disc is protected by a layer of wax, only the sections exposed to the solution – where you carved your words – will dissolve.
On the negatively-charged wire (the cathode), water is reduced, releasing gaseous hydrogen and hydroxide ions.
Meanwhile, the hydroxide ions released during this process react with ions of copper(II) and iron(III) to create the corresponding hydroxides, which precipitate.
On the anode:
Cu0 - 2e = Cu2+
Fe0 - 3e = Fe3+
On the cathode:
2H2O + 2e = H2↑ + 2OH-
In the solution:
Cu2+ + 2OH- = Cu(OH)2↓
Fe3+ + 3OH- = Fe(OH)3↓
Safety precautions: work in protective gloves, eyewear, and a mask. Perform the experiment in a well-ventilated area.