How to Turn pennies into silver and gold coins with zinc
One of the most famous and repeated chemistry experiments involves money. Some would say this is more of a trick than an experiment, but you can be the judge of that. No one can just turn pennies into silver or gold coins, but someone with a few chemicals can. So, if you want to cooler cents in your pocket, try out this chemistry trick yourself. Nurd Rage (Dr. Lithium) shows you how to turn pennies into silver and gold coins using zinc.
First, get 30g of zinc sulfate and dissolve it into 100mL of water.
If you don't have zinc sulfate or can't make it, you can also use zinc chloride. This can be made by simply mixing hydrochloric acid with zinc metal and waiting until the fizzing stops.
Then, drop in several cut strips of zinc metal.
The solution is heated to a boil and copper pennies (that have been thoroughly washed and cleaned) are dropped in. They must touch the zinc in order for this reaction to work. Leave it in for five to ten minutes.
The zinc metal dissolves and releases electrons that go into the copper and give it a negative charge. The zinc ions in solution now redeposit form a thin layer of zinc metal. This gives the coin a silvery color.
Overall, we're going from zinc metal to zinc metal and at first it seems like we're missing something about thermodynamics. What is the driving force? Some claim it's a surface free energy issue with zinc having a lower potential on copper than in free solution (at high concentration). Others state that it's an alloy of zinc metal and copper on the surface. The silvery color you're seeing on the penny is actually a type of white brass, not pure zinc. This is thermodynamically more favorable than pure separate metals and thus serves as the driving force.
Brought to you by one of WonderHowTo's favorite scientists, NurdRage.