Copper mirror

Copper on the bottle's walls, who's the fairest of them all?

Difficulty:
Danger:
Duration:
6 hours

Reagents

Safety

  • Put on protective gloves and eyewear.
  • Conduct the experiment on the safety underlay.
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

Can I obtain a mirror from another metal myself?

Of course! An equally impressive silver mirror can be obtained relatively simply. Watch this video to learn how!

Step-by-step instructions

Prepare a solution of sodium acetate CH3COONa and sodium ascorbate in a bottle.

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Add some copper sulfate CuSO4 solution.

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Expose the mixture to light to speed up the reaction. Observe the result after several hours—the inside of your bottle is covered with a reflective layer of copper!

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Pour out the contents of the bottle.

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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

It may seem that metallic copper materialized on the inside of the bottle out of nowhere. In reality, it was there all along. The CuSO4 solution you added contained Cu2+ ions , which are just two electrons away from becoming metallic copper Cu.

There are many ways to provide Cu2+ ions with the two electrons they need in order to turn into metallic copper Cu. Not all of them would allow a shiny copper coating to form, though. In a different experiment from this box, Cu2+ ions also gain electrons, but form an intricate copper dendrite instead of a shiny, foil-like film. In fact, making a copper mirror requires quite a peculiar set of conditions.

In this particular instance, it's the ascorbate ions  from sodium ascorbate that give Cu2+  electrons. However, they’re slightly reluctant to do so in the dark, which is why you need to shine light on them. Simply having a fitting donor of electrons isn’t enough on its own, either. You also need CH3COONa to ensure that the copper doesn't just sink to the bottom of the bottle as a boring powder, but rather neatly sticks to the bottle's walls.

That’s interesting!