Copper tree

A copper tree grows inside a layer of salt

4 days
Experiment's video preview



  • Put on protective gloves and eyewear.
  • Conduct the experiment on the plastic tray.
  • Keep the growing tree out of reach of children under 12 years old.
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

Although 2 or 3 days have passed, the tree does not grow

Normally, a copper tree starts growing on the next day after the beginning of the experiment. However, sometimes you cannot witness it. If nothing happens in 3 days, something is probably wrong.

Inspect the metal granules. Make sure they are dipped in the salt. Without taking them out, check whether the granules look any different now or not. Try to dip them a bit deeper and leave it for several more days.

Why in step 6 water should be added slowly and dropwise?

If you add the water too quickly then an air gap can form between the crystals of the salts. Becasue of this air gap the reaction won't start and the tree will not grow.

Step-by-step instructions

Step-by-step instructions
  1. Pour two big spoons of of copper sulfate pentahydrate CuSO4·5H2O into a vial.
  2. Add 10 drops of water.
  3. Pour in 3 big spoons of sodium chloride NaCl.
  4. Take a bottle with zinc Zn pellets.
  5. Put 3 pellets on top of sodium chloride NaCl.
  6. Slowly drip water into the vial, until the salt becomes wet throughout (about 40 drops). Note: if you drip too fast, it may cause an air plug, and the reaction won’t go.
  7. In a day, you’ll see a copper tree growing in the vial. In 3–4 days, the tree will become even larger!

Graphical step-by-step instruction

Expected result

In a week in the depths of the salt a copper crystal grows, bending around salt crystals and taking an odd shape, similar to a tree branch.


Dispose of solid waste together with household garbage.

Scientific description

Why does the copper tree grow?

If a zinc pellet is put into a copper sulfate solution, it will soon be covered with a thin layer of copper. In this case, the following reaction takes place:

Zn + CuSO4 → ZnSO4 + Cu

This reaction is of oxidation-reduction type, which means, that the main role in this reaction belongs to electrons. Electrons move from Zn, giving zinc ion Zn2+, to copper ion Cu2+ in copper sulfate, turning it into metallic copper, which covers the zinc pellet.

Zn0 – 2e → Zn2+

Cu2+ + 2e → Cu0

The chemistry behind our experiment is the same, the only thing that has changed is the presence of salt sodium chloride NaCl. It separates zinc pellets from copper sulfate, which makes the reaction rate slower. Slower reaction rate means that the metallic copper, which forms during the experiment, has enough time to arrange its atoms into beautiful shiny branchy crystals. This is how the copper tree grows.

The reagents are separated from each other. How does the reaction proceed?

As it has been mentioned earlier, the reaction between copper sulfate and zinc takes place because of the electron transfer from zinc to copper ion. Interestingly enough, sodium chloride does not hinder this process – it just makes electrons to pass a little bit longer way. This is why the reaction rate slows down and we need to wait for so long till the tree grows.

Why does the solution in the vial turns green during the experiment?

When water is added to the reaction mixture, copper sulfate and sodium chloride begin dissolving. As they dissolve, they dissociate into ions:

CuSO4 → Cu2+ + SO42−

NaCl → Na+ + Cl

When copper ions meet chloride ions, they form tetrachlorocuprate [CuCl4]2− – a complex compound, which has intense green color.

Cu2+ + 4Cl → [CuCl4]2−

Follow up

A big copper tree

No doubt, a copper tree grown in the vial is cool. Unfortunately, you hardy can take it out of the vial. Here, we will tell you how to grow a big copper tree and to draw it out of the cup where was grown.

What do we need for the experiment?

  • 10 grams of copper sulfate pentahydrate (cupric sulfate) CuSO4*5H2O-should be no problem finding it in a gardening or DIY store section or at an online chemical store;
  • 100 grams of coarse cooking salt NaCl (note: the experiment will not work with fine grain salt!);
  • a plastic cup (you may take one from the starter kit);
  • an iron nail, a paper clip or another small iron object (preferably without any coating);
  • plastic wrap, a Petri dish or a plastic lid that fits the cup;
  • protective gloves;
  • water.

Take an empty plastic cup and pour 10 g of copper sulfate into it. Evenly spread the blue crystals on the bottom. Add coarse salt (100 g) on top of copper sulfate crystals. Moisten the salt with a bit of water: 15-20 mL should be enough for the experiment (you can measure 2-3 plastic vials from the “Copper tree” experiment). Salt in the cup should be wet, but there should be no extra liquid. Put the chosen metal object on top and imbed it in salt. Seal the cup tightly with plastic wrap, so that water will not evaporate. Leave the cup for 1-2 weeks at room temperature. If water does dry out (which is most likely if a lid was chosen), gradually add more water into the beaker at a rate of 1 vial every 3-4 days.

In 1-2 weeks, remove the cover. Add 75 mL of water into the cup. Gently turn the plastic cup over the cup, and place its contents in water. Gradually, as the salt dissolves, it will reveal a copper tree. When it is completely free of salt, gently remove the tree from the cup. If not-drain the water and add more fresh water.

Don’t forget to send us photos of your big copper tree!