Turn Copper Pennies Into Silver and Gold [Chemistry Trick]





Introduction: 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.



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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.

Hi ,

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

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.