Copper vs. Copper

Draw by dissolving!

Difficulty:
Danger:
Duration:
40 minutes
Copper vs. Copper

Reagents

Safety

  • Put on protective gloves and eyewear.
  • Conduct the experiment on the plastic tray.
  • Observe safety precautions when working with boiling water.
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

Which plate is copper?

This set contains two types of plates: copper and iron. The iron plates are grey. The copper plates have a characteristic pumpkin-orange color.

How long should I polish the CEM plate?

The experiment depends on how well you polish the plate. You have to polish any traces of dirt away. In general, the entire surface should acquire a light-pinkish hue.

Why can't I touch the polished surface without gloves?

Traces of oils from your fingers (even freshly washed) can remain on the metal. The reaction won’t happen in these spots, which can mar the result.

I didn’t apply the sticker very well – can I reapply it without repolishing the plate?

No, you’ll have to polish the plate again. Any glue particles left on the metal can interfere with the experiment.

How can I stir the contents of the beaker? The beaker’s full of boiling water.

No worries! If you added the right amount of water (35–40 mL), the beaker will just barely be warm. It will be safe to hold by the rim, as shown in the instructions.

The copper hasn't dissolved after 7 minutes. What should I do?

First, make sure that you added all the correct reagents to the solution. Continue swirling the beaker for a bit — if the water wasn’t hot enough, the process could take longer. If neither of these steps works, it’s possible that you didn’t polish the plate enough. In this case, you will have to start the experiment over.

When I took the sticker off, it left some ugly stains.

Don't worry! This is just glue. Use some soap, a sponge, and warm water to wash it off.

Step-by-step instructions

The surface of the polymer base is covered with a layer of copper. Make sure it's nice and clean.

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Now protect some of the copper with a sticker of your choice.

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Submerge the plate in a hot solution of sodium chloride NaCl and copper sulfate CuSO4.

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The unprotected copper Cu0 engages in a chemical reaction with the copper from CuSO4, which is present in the solution as Cu2+. They both turn into a third form of copper, Cu1+, which does not stick to the copper or the polymer plate.

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After removing the sticker, you get a nice keychain!

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Disposal

Dispose of solid waste together with household garbage. Pour solutions down the sink and wash with an excess of water.

Scientific description

What exactly happened with all the coppers (on the plate, from the copper sulfate CuSO4, and whatever they turned into during the reaction)? As it turns out, metallic copper consists of copper particles  packed with a whole cloud of electrons  so that there are just enough electrons for each copper particle. The copper particles in the metal are called Cu0 (the “0” means that the particle isn’t missing electrons, and doesn’t have any extra electrons either). The copper particles from the copper sulfate, however, are missing exactly two electrons each , and are thus called Cu2+ (for the number of electrons they are missing).

In certain conditions, particles can share their electrons with similar particles that are lacking some electrons. In this case, these conditions being the presence of sodium chloride NaCl and hot water, Cu0  gives one electron  to Cu2+ , which makes them both turn into Cu1+ . Eventually, all the unprotected metallic Cu0 becomes Cu1+, which doesn't stick to the copper or the polymer plate.

In one particular field of engineering, the ability to easily create complex metallic patterns comes in very handy. Electric circuits in modern electronics require an impossible number of wires to operate. Luckily, instead of separate wires, one can just print the circuit with metal in pretty much the same way you just printed a picture. The result is called a "printed circuit board" , which you can find inside pretty much any electronics  these days.

That's interesting!

Why polish the copper surface?

To ensure an even and accurate result, the CEM plate (composite epoxy material) should be polished to remove any dirt, glue particles, and even traces of oil from your fingers. In addition, a protective copper oxide film may have formed on the surface of the copper. This film has a protective role in the main part of the metal. All of these elements serve as a kind of barrier and impede the reaction, preventing the Cu0 from reaching the reagents it is supposed to interact with. This muddles the result significantly.

On a commercial scale, chemical, electrochemical, and mechanical methods are used to obtain the same cleaning result. Sometimes just one method is sufficient, whereas other cases, depending on the material, require a harsher approach. In addition, the surface of the copper can exhibit various irregularities and scratches. Mechanical polishing removes all of the above impurities, often along with the top layer of metal, which is sometimes unnecessary.