In this simple chemistry demonstration or crystal project you’ll grow a silver crystal tree. This is a variation of the classic method of growing silver crystals on a copper wire.
Silver Crystal Tree Materials
You only need two materials for this project:
- Sheet of copper that has been cut into a tree shape or a tree made from copper wire
- 0.1 M Silver nitrate solution
There are a few different ways to make the tree shape. One of the easiest is to spiral copper wire over a paper or cardboard cone to make a simple tree form. Another method is to wrap thin copper wires around a thinner one, leaving the ends of the thin wires out as branches. Another method is to use tin snips to cut a tree shape out of a thin copper sheet.
Be careful to use uncoated copper. Because copper oxidizes in air, it is often treated or coated.
Grow a Silver Crystal Tree
All you need to do is place the copper tree into the silver nitrate solution. Silver will be reduced on the copper, forming silver crystals. Crystals begin forming immediately and should be visible within an hour. You can allow the silver crystal tree to sit in an undisturbed location for a day or two for peak crystal growth. When you are finished growing the silver crystals, you can remove the tree from the solution and use it as a decoration.
How It Works
A displacement reaction is responsible for crystal formation:
2 Ag+ + Cu → Cu2+ + 2 Ag
The silver nitrate in water dissociates into silver and nitrate ions. The silver and copper “trade places” so that silver metal takes the place of some copper, while some copper goes into solution. The copper ions change the color of the liquid, making it blue.
Copper isn’t the only metal that works for this project. Silver will also replace mercury. However, mercury is toxic. If you happen to have mercury sitting around, you could place a bead into a container of silver nitrate and see the same effect.
Dendritic Silver Crystals
Silver crystals form dendrites, which look like ferns, branches, or trees (depending who you ask). Another simple project is to place a copper wire in silver nitrate solution and view crystal growth using a magnifying glass or microscope. The intricate structure of the metal crystals develops as you watch!
Here’s an example of the reaction on a piece of copper: