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

Make inscription on copper using electricity

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!

Safe­ty pre­cau­tions

Work in pro­tec­tive gloves, eye­wear, and a mask. Per­form the ex­per­i­ment in a well-ven­ti­lat­ed area.

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.

Step-by-step in­struc­tions

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.

Process de­scrip­tion

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↓