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Safety: Warning! Copper sulfate is an irritant. Harmful if swallowed. If
swallowed, give water and call a physician. In case of contact with eyes or
skin, flush with water. For eyes, get medical attention. Keep out of the reach
of children. Be sure to rinse any solutions down the drain with lots and lots of
water. After you are finished with your Homemade Geode, wrap it in plastic and
place it in a covered trash can.
About the Experiment
This
experiment allows one to grow crystals of copper sulfate by way of temperature.
Copper sulfate is more soluble in warm water than cool water.
First, one
dissolves an excess amount of copper sulfate in water. What we mean by "an
excess amount" is that one adds copper sulfate with gentle stirring to the warm
water until no additional copper sulfate solid can be dissolved into the
solution. This creates a solution that chemists and the Village People call
"saturated." The solution is allowed to cool. As it turns out, one can add more
copper sulfate to a warm solution than a cool solution. So what happens when the
solution cools? The copper sulfate cannot stay in the solution. Instead it forms
crystals. So in this experiment, one initially grows crystals by using a
Temperature Method. If the experiment sits for more than a day, then some water
will evaporate from the solution. The copper sulfate cannot evaporate and stays
behind. As more water evaporates, there is less room for the copper sulfate to
hang out in the water (think crowded room). So to make the best use of the
space, the copper sulfate molecules gets together with one another in a very
organized way. Think of chairs lined up in rows in an auditorium, or cars parked
in a large parking lot, or best yet, cars parked in a multiple story parking
lot. The crystals grow larger as more and more copper sulfate molecules (cars)
pile onto the crystal (parking garage full of cars).
Geodes? Mother
nature's parking lot for minerals. Geodes are rocks, where lots of minerals and
water passed through and into the rock. After millions of years the water moves
on (evaporates) leaving the minerals behind, and voile! Crystals! So your
eggshell containing copper sulfate crystals is a quickie
geode.
Protocol
1. Obtain a clean eggshell. In other
words, carefully crack open a chicken egg, discard the egg and keep the
eggshell. Since we are using the eggshell to hold the solution, try to open the
egg without making to many cracks in the shell (create two halves for examples,
or try to take off just the end of the shell for a different effect). Clean the
egg from the shell.
2. To 1/4 cup of hot water in a separate
container (not the eggshell yet), add some copper sulfate. Stir. Add copper
sulfate and stir until no more copper sulfate can be dissolved in the hot water.
For the best crystals do not add way too much copper sulfate. Add just enough so
that only a small amount (a few pinches) of solid material cannot be dissolved
into solution.
3. Pour the copper sulfate solution into the
eggshell(s).
4. Place the eggshell(s) in an area where they will
not be moved, spilled or disturbed for at least two to three days. Avoid placing
the shells containing the solution where someone might eat, break or spill the
experiment. Be sure to place the eggshell in or on something to protect what
ever sits underneath (a table or counter for example) in case the eggshell(s)
leaks.
5. Observe the solution in the shell each day. Crystals
should appear after the first day and will be looking most excellent by day two
and three.
6. For a better view of the crystals, remove and
discard the solution after a few days or a week or two. Allow the crystals to
dry in the eggshell. Cool eh?
Point to Ponder
What would
happen if we added a lot of water to the homemade geode or placed the homemade
geode in a container with a lot of water? Do you think the crystals would
remain, or would they dissolve? Why?
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