Instructables

Turn Copper Pennies into Silver and Gold [Chemistry Trick]

video Turn Copper Pennies into Silver and Gold [Chemistry Trick]
In a display of alchemy we turn copper pennies into silver and finally to gold. Obviously it's a chemistry trick but still impressive.

First we get 30g of zinc sulfate and dissolve it into 100mL of water.

Zinc sulfate was made back in our video on making a copper sulfate and
zinc battery: http://www.youtube.com/watch?v=Id3tL2iI0Vw

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 we drop in several cut strips of zinc metal.

Zinc metal was obtained from our video on getting useful materials from batteries: http://www.youtube.com/watch#%21v=knc1lSupAwQ

The solution is heated to a boil and copper pennies, that have been thoroughly washed/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. Giving the coin a silvery color.

Now the smart physical chemist might wonder how this can possibly work. 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? I've searched the literature and there doesn't seem to be a consensus among scientists, 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.

Anyway, whatever the specific chemical reason, we've now deposited zinc onto copper.

The most amazing trick is to turn it into gold. Simply wash the coin and place it on a hotplate heated to about 300 Celsius. As it heats the zinc will diffuse into the copper, forming brass on the surface that looks like gold.

Eventually it will wear off but the results are rather impressive.
vaibhavg12 days ago

Hi ,

Want it to know purity level of the gold which we had created and also weight

sheneel1 month ago

I have to silver plate a copper bracelet but i can't increase the mass by more than 5g. what to do?

ChmE1 month ago

I am fairly certain you are mistaken. If not, then I may be but would like an explanation of course.

The reaction in which Zn(s)+2NaOH-->[Zn(OH)3H2O]-Na+ Does not just release 2 electrons. Hydrogen gas is evolved so while zinc is oxidized, hydrogen ions are reduced to their elemental state in a perfect 1:1 ratio with zinc. So that leaves the question: How/Why does the zinc(II) ion end up plating onto the penny?? It isn't even thermodynamically favorable as a cell...

I do commend you for your very rational entropy explanation for the silvery film that is the alloy.

NurdRage (author)  ChmE1 month ago
Your reaction equation is wrong, there is no sodium hydroxide used anywhere in this experiment
MrDrSmith7 months ago
Finally an explanation that makes sense.

"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"

I really like this explanation. It's a simple entropy argument. Zinc alloy is preferred over pure zinc because it's less ordered. Entropy always increases.
gaspersimon10 months ago
Can you please post some literature links or titles.
Tnx
Gerrles3 years ago
I cant make the materials because i dont have time , so do u know where i can buy or substitute zinc sulfate and zinc metal
(Im not using the internet for this stuff)
in fact you are using the internet for this because you asked via the internet
hi my all dears, i respect all of you i admire your skills, i am a alchemist professionally. i am very near to show my experiment on copper conversion to silver. i have a problem here which i want to share with experts like u all here,i have need of potassium nitrate in an oil form, an oil form that must be oil on heating's, mean it may not to evaporate on heating's be stable having all the basic properties of kno3, this oil form of kno3 is my final obstacle to my dream, remember its not a cheap or fake notice, any one having interest in alchemy will understand that what am saying that is WHAT, so one who has such a strong knowledge please help me on the reward i will give him my formula after my discovery of low energy synthesis process of copper conversion to..................awesome.
paullene2 years ago
is the silver coating on the wire permanent? please please i need you helppp
Rebreg paullene2 years ago
No
hi there. I want to know why the zink around the cupper coin (from the experiment turning cupper coins into gold) turns to gold when you heat it. thanks!!!! :)
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wait... it says brass... shoot. Sorry for being redundant right there.
a side note is that all you have to do is heat most pennies since they are zinc cores plated with copper.
When I look up zinc sulfate on eBay, most of the results say "zinc sulfate mono hydrate." Does the "mono hydrate" mean anything, and if so will it change the reaction?
the mono hydrate means it has 1 water molecule in it
NurdRage (author)  ElectricUmbrella3 years ago
it'll still work, go for it :)
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NurdRage (author)  chemicallypsycho3 years ago
But it has no clothes, just the color is being changed.
that was a mediphor... shouldnt the title be named changing coppers color to gold and silver. It looks like your creating nothing more then a copper alloy. Im a huge science lover. Im just looking for new ideas to make cash. I thought ill try doing something that i like.
NurdRage (author)  chemicallypsycho3 years ago
the title is also a "mediphor"
is it passable to chemically change a copper element to a gold or silver? Or any other element for that matter. Perhaps by add or subtracting excisting protons Ion or nuetrons? Fussion proccess maybe?
NurdRage (author)  chemicallypsycho3 years ago
nuclear fusion can turn elemental copper into elemental gold. but that is beyond the ability of the home chemist.
Its also common knowledge that pennies are not all copper. Is the partner metal also effected by this experiment?
giovibleu3 years ago
Hi Nurd! I don´t undestand about chemistry.
so, do this trick also works with silver ?
or is there another way to get this effect?
thanks!
Danny5743 years ago
I've done it with a 30% sodium hydroxide solution and zinkpowder two years ago as christmaspresant.
Guppy83 years ago
Could this be done with aluminium sulfate, aluminium metal, and copper?
mahirh4 years ago
displacement reaction in short thanks!
joosh4 years ago
I did this in my chemistry class for our first lab. Hmm... I still have my lab some where in my lab manual and now I want to go find it.
mikeasaurus4 years ago
neat trick. how long to have the coating wear off and the coin returns to a copper colour?
rimar20004 years ago
Very interesting. 

I learned to cover with zinc a piece of metal (iron or bronze in my case) using a plastic brush soaked in zinc chloride, connected to the positive pole of the battery charger.