Lead the students through the following demonstration or instructions:
- Dissolve as much of the washing soda/Epsom Salts as you can in very warm water. Arrange two jars on a windowsill with a saucer in between. Fill them about half way with the supersaturated solution.
- Tie a weight (such as a paperclip)to each end of a piece of yarn. Soak the yarn in the solution. Place the yarn so that each end is well inside the water solution in each jar and the middle is over the saucer. Make sure that the loop of the yarn is hanging lower than the water levels inside the jars. (See diagram on included worksheet).
- Put just a touch of dry washing soda on the saucer.
- Leave the jars for several days.
- The solution in the jars will wick along the yarn, then drip off at the low point in the middle onto the saucer. Deposits should build up on the saucer and hang from the yarn and may eventually connect to form a "column."
- Set up the second set of jars at the same time. Follow the same procedure except use the baking soda instead of the washing soda. Within 48 hours, students will notice the crystals look very different by comparison. (They will look like a delicate cavern flower.)
- Label the first set of jars A and the second set B. (A different drop of food coloring in each of the solutions, when mixing, will make it easier for younger students to discuss differences.) Have students check the experiment daily and record the results on the "Growing Cavern Crystals" worksheet included.
Grades 9 - 12 "Crystal Growing Experiment"
Using the same experiment as described above, students can observe effects on the deposition process by manipulating some of the variables, such as varying solutions by concentration and by environment (light and dark locations, warm and cool, or sealed and open). Have students predict what might happen. After results are recorded and compared, ask the following questions:
- Which conditions were the most favorable for growth?
- What do these conditions have in common?
