Growing Crystals from Solutions

Delores E. Jackson             Richard Byrd School
                               363 West Hill Street 
                               Chicago, Illinois 60610
                               312-280-4000

Objective:

Grades 2/3 
Forming crystals in three-dimensional patterns from solutions.

Materials:

 (1) Sugar (C12H22O12)
 (2) Potassium sulfate (K2SO4)
 (3) Epsom salts (magnesium sulfate - MgSO4)
 (4) Baking soda (sodium bicarbonate - NaHCO3) 
 (5) Sodium ferrocyanide (Na4Fe(CN)6.10H2O)
 (6) Ammonium ferric sulfate (NH4Fe(SO4)2.12H20)
 (7) Eight large test tubes with one-hole stoppers to fit
 (8) Eight circles of copper wire
 (9) Thread                           
(10) Hot water
(11) Hand lens or magnifying glass

Strategy:

(1) Fill the first test tube with hot water.  Add the sugar, a small amount at a 
    time, and stir with a glass stirring rod until no more sugar dissolves. 

(2) Tie a six inch piece of thread to a circle of copper wire.  Pass the other 
    end of the thread through the hole of a one-hole stopper to fit the test
    tube. 

(3) Put the copper wire in the sugar solution and insert the stopper in the 
    tube.  Adjust the length of the thread so that the copper wire is about 
    0.5 in. from the bottom of the test tube.  Hold the thread in place by taping 
    it to the stopper with a small piece of masking tape.  Keep the hole in the 
    stopper open. 

(4) Set the tube aside where it will be undisturbed for 3 or 4 days. 

CAUTION Sodium ferrocyanide is poisonous, so be extremely careful when 
conducting this experiment.  Suggested powders for Primary grades; soda, epsom 
salt, salt, sugar. 

(5) Repeat the procedure with the following chemicals: potassium sulfate 
    ammonium ferric sulfate, magnesium sulfate (Epsom salts), sodium bicarbonate
    (baking soda), and sodium ferrocyanide.  Add each chemical to a tube half 
    filled with hot water and stir until no more solid will dissolve.  Be sure to 
    label each tube. 


(6) After crystals have formed on each string, carefully remove each string from 
    its tube and describe the crystals. 

(7) To help you describe the shape of each crystal, model patterns are provided. 
    Cut out each model and fold it into the proper shape.  These six geometric 
    shapes represent some of the basic structures found in crystals. 

(8) Using these models as a guide, examine each crystal with a small hand lens 
    or magnifying glass and describe completely each crystal, including its 
    size, color, clarity and shape.  Compare your results with those of your 
    classmates.