Grow a Crystal Tree
In this hands-on science activity, kids grow crystals on a tree overnight.
A crystal is a solid that has an ordered molecular structure. (Other solids have a random molecular structure.) Snowflakes, diamonds and salt are all examples of crystals. For example, if you look at salt through a magnifying glass, you will see that the grains are all the same shape (though they may be different sizes), with straight edges and flat surfaces. Some mineral crystals, like salt, are created when the mineral separates out of a solution (“precipitates”) and collects into crystal forms -- usually forming around a particle of dust or similar. That is how the crystal trees in this activity are grown: the salt crystals precipitate out of the solution as the water evaporates, then cluster together around the particles in the bluing solution and attach to the side of the tree.
Crystals form when a melted mass of matter starts to cool. As it cools, the atoms arrange themselves into a repeating pattern. There are seven types of crystal structures: cubic (silver, gold, diamond, salt), tetragonal (silicon), hexagonal (ice, snowflake, quartz), orthorhombic (topaz, Epsom salt), rhombohedral (calcite), monoclinic (gypsum), and triclinic (turquoise).
Ice crystals grow directly from condensing water vapor in the air, usually around a nucleus of dust or some other foreign material. Snow flakes are a complex arrangement of loosely connected ice crystals. There are two main types of ice crystals: basic plate-like forms with a six-fold symmetry and basic column-like forms, such as needles or hollow columns. The type of crystal that forms depends mainly on the temperature and supersaturation level in the cloud where the formation takes place.
Do not let children touch the hot water.
- Sponges or sponge paper cut into a tree shape - 1-2 of this item per student
- Salt (any kind) - 2 tablespoon per student
- Very hot water - 2 tablespoon per student
- Mrs. Stewart's Bluing Solution - 2 tablespoon total
- Deep dish that is not much larger than the sponge - 1 total
- Food coloring (optional)
- Ammonia (optional) - 1 tablespoon total
- Magnifying glass (optional)
Cut your sponge(s) into the shape of a pine tree and place into a small dish, not much larger than the sponge.
Dissolve the salt in the hot water by stirring for about 1 minute. It likely will not dissolve completely. Stir in the bluing solution (you can buy it here) and optional ammonia.
Place the tree-shaped sponge into the dish. Dot with food coloring (optional).
Pour the salt solution AROUND the sponge but not on it. Allow the sponge to slowly absorb the solution.
As the water evaporates, crystals will begin to appear. Crystals may begin to appear with the hour; your tree should be covered within a day or two, depending on the rate of evaporation.