Alchemy

Turn copper silvery without using magic!

Difficulty:
Danger:
Duration:
50 minutes

Reagents

Safety

  • Put on protective gloves and eyewear.
  • Conduct the experiment on the safety underlay.
  • Keep a bowl of water nearby when working with fire.
  • Remove protective gloves before lighting the splint.
  • Keep flammable materials and hair away from flame.
  • Do not extinguish the solid fuel. Let it burn down completely.
  • Do not touch the stove after the experiment. Wait until it cools down.
General safety rules
  • Do not allow chemicals to come into contact with the eyes or mouth.
  • Keep young children, animals and those not wearing eye protection away from the experimental area.
  • Store this experimental set out of reach of children under 12 years of age.
  • Clean all equipment after use.
  • Make sure that all containers are fully closed and properly stored after use.
  • Ensure that all empty containers are disposed of properly.
  • Do not use any equipment which has not been supplied with the set or recommended in the instructions for use.
  • Do not replace foodstuffs in original container. Dispose of immediately.
General first aid information
  • In case of eye contact: Wash out eye with plenty of water, holding eye open if necessary. Seek immediate medical advice.
  • If swallowed: Wash out mouth with water, drink some fresh water. Do not induce vomiting. Seek immediate medical advice.
  • In case of inhalation: Remove person to fresh air.
  • In case of skin contact and burns: Wash affected area with plenty of water for at least 10 minutes.
  • In case of doubt, seek medical advice without delay. Take the chemical and its container with you.
  • In case of injury always seek medical advice.
Advice for supervising adults
  • The incorrect use of chemicals can cause injury and damage to health. Only carry out those experiments which are listed in the instructions.
  • This experimental set is for use only by children over 12 years.
  • Because children’s abilities vary so much, even within age groups, supervising adults should exercise discretion as to which experiments are suitable and safe for them. The instructions should enable supervisors to assess any experiment to establish its suitability for a particular child.
  • The supervising adult should discuss the warnings and safety information with the child or children before commencing the experiments. Particular attention should be paid to the safe handling of acids, alkalis and flammable liquids.
  • The area surrounding the experiment should be kept clear of any obstructions and away from the storage of food. It should be well lit and ventilated and close to a water supply. A solid table with a heat resistant top should be provided
  • Substances in non-reclosable packaging should be used up (completely) during the course of one experiment, i.e. after opening the package.

FAQ and troubleshooting

Is it possible to carry out these transformations in the opposite direction?

Did you think that the “magical” transformations were over? Far from it!

To turn a “silver” or “gold” coin back into a copper one, you need to immerse it in an acid (you might be able to find citric acid in your kitchen, for instance). As you may recall, the "silver" coating on your coin is just a layer of zinc covering the copper, and the "gold" is brass, which is a layer of mixed copper and zinc particles. Acids will react with zinc, changing its form from metallic to ionic, and leave copper untouched. As a result, only pure copper will be left on the surface of the coin.

But what if you want to turn a “gold” coin back into a “silver” one? No problem! Try to coat it with zinc just like you did at the beginning of the experiment. This coating should stick well to brass, too!

Try all the possible options and enjoy your new status as "alchemist: master of the Philosopher's Stone"!

Step-by-step instructions

You're going to need a lot of heat for this experiment. Solid fuel can provide just enough.

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Add some zinc sulfate ZnSO4 solution—it contains Zn2+ ions. Ammonium chloride NH4Cl will help them move through the solution and interact with the other participants of this reaction.

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Put a copper Cu coin and zinc Zn rod in the mold. The Zn that makes up the rod and Zn2+ in the solution are two different forms of the same element: Zn particles are covered by an electron blanket, while Zn2+ float freely in the solution. Instead of a copper coin, you can use a copper coin—just make sure to wipe it clean.

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The copper coin turns silvery right before your very eyes!

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To make the coin look even fancier, rinse it with water. But did you really manage to convert copper into silver?

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Disposal

Please refer to local regulations when disposing of chemicals. Dispose of other solid waste with household garbage. Pour leftover solutions down the sink. Wash with an excess of water.

Scientific description

For centuries, the chemists of the past—alchemists—strove to transform cheap and abundant metals like copper into rare and valuable silver and gold. But little did they know that their task was absolutely hopeless! With later scientific advancements, it became clear that chemistry can only rearrange atoms, not convert them into one another. Was the mysterious transformation you just witnessed simply an example of such a rearrangement?

Yes! Both the zinc Zn  in the rod  and the copper Cu  in the coin  exist in the form of positively-charged particles (  and ), enveloped in a cloud of negatively-charged electrons . The positively-charged zinc particles Zn2+  are more mobile than the particles of copper —when heated, they begin jumping out of this cloud into the solution  and settling back down . But occasionally, they settle on the copper  instead of the zinc, since their electron clouds are too close to each other. As a result, the copper coin is covered with a layer of zinc , which resembles silver.

The coin is still "silver," not "gold"—can you transform it further? Yes! In fact, it's surprisingly easy! If you carefully heat the coin with a candle, zinc particles from the surface will “sink” into the copper atoms underneath, resulting in a surface made of a mixture of the two . This mixture of zinc and copper is called "brass," and it looks pretty golden!

Although it's impossible to make a different element by merely rearranging atoms, modern science knows how to change the atoms themselves! Today's nuclear physicists can routinely turn one element into another. But that's a completely different story...

That’s interesting!