Turn Copper Pennies Into Silver and Gold [Chemistry Trick]





Introduction: Turn Copper Pennies Into Silver and Gold [Chemistry Trick]

About: NurdRage is a dedicate group of science nerds trying to further amateur science with direct how-to instructions in video format. We saw what was already online and we thought "we could do better".....

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.



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it is real gold????????????????????????????????

i came looking for copper but found gold

i take gold from old gold coted materials

You can use a safer reaction of Zinc Chloride 1M solution boiled with zinc metal. Then add the pennies, wait 10 minutes. Take them out and rinse them off, they will be silver. Then place them on low heat of hot plate or flame gently until they turn gold. Also clean the pennies first with salt water and vinegar to make them shiny before doing the experiment. They will be much more attractive than the ones above.

1 reply

Hi ,

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

2 replies

It's not Au gold. It is copper and zinc melted together forming brass.

This experiment does not create gold. It only plates a zinc alloy on the penny that when heated turns a goldish colour. This is a standard classroom assignment in most high school chemistry classes.

can we use zinc metal powder in place of zinc metal pieces for experiment .and plz tell me what is the difference between zinc metal strips and zinc metal powder.

1 reply

zinc powder makes dust which is highly flammable and so is not recommended. Better to have zinc strips or zinc granular.

Alchemy is just basic life to more mature but soon it becomes equivalent exchange you always need the ingredients befor u start. And with this. It's basic equivalent exchange !!! :) right?

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1 reply

just so you know... transmutation of elements is still illegal. Believe it or not. Kind of funny actually, I guess it one of those really old (about 200 years old) blue laws that never came off the books.

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


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.

1 reply

Your reaction equation is wrong, there is no sodium hydroxide used anywhere in this experiment

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.

Can you please post some literature links or titles.