Crystals and Caves

Perhaps the most exciting part of a science class is doing some sort of experiment.  Watching a science concept progress day-by-day in the class itself helps the information become more real to the students.  One of the experiments that the third and fourth grade classes have done this last semester has been to create an example of how cave formations actually form.  While this experiment does take a while to progress, the results are certainly fascinating.  (Also a minor warning: it can be a little messy if one is not careful.)

Many places on the internet have different ways to do this experiment, but  I chose this one, so that the students could see how nature might take its course in real-time.  This one was found under the search title “DIY Crystals”.  It requires a plate (one that you do not mind getting messy), about six to seven inches of string (preferably a thicker string, like yarn), two glass jars (ours were smaller, so any size around four to five inches tall [or ten to twelve centimeters] should be acceptable), two small things to be used  as weights that can have string tied around it and will fit in the jars easily, two different food coloring colors, hot water, and as much baking soda as can fill the jars.

Whew!

(Again, it is important to remember that this can get a little messy, but it should be manageable.)

Before beginning, it would be helpful to discuss what evaporation and the states of matter are.  These concepts are key to helping children understand the process more fully.  Both work together to help form what are known as “stalactites” and “stalagmites” in caves.  For instance, this video on the states of matter has a great way to explain and show what each state looks like  https://www.youtube.com/watch?v=JQ4WduVp9k4 .  There is also this video about evaporation https://www.youtube.com/watch?v=ncORPosDrjI .  You could also look up the “water cycle” and several videos or other information sites will give you plenty of options.

In a low-traffic area, place the plate between the two glass jars.  Add around six to seven tablespoons of baking soda to both jars and add hot water to them.  Then, stir the baking soda and food coloring, until they dissolve.  Tie the two weights to the ends of the strings, so that it won’t slip out of the jars at any time. Place both weights into the jars, so that the string can absorb the water.  Last, simply wait for five weeks or so and watch your stalagmites form like they might on the roof of a cave!

The third and fourth grade classes had fun taking turns setting everything up and helping mix the solution together.  Everyday, they were eager to see the progress that the solution was making.  We used red and purple in the separate jars, and the colors formed some interesting and strange shapes.  It did not take too long for the water to evaporate and leave the hardened baking soda to droop off of the string.  The baking soda also spread over the plate, which dried and hardened.  The liquid also got all over the tabletop…somehow…(I think I can guess…wink, wink…) But, in case you wondered, the baking soda did come off, and the plate was saved!  (cue massive applause)

Thank you for taking the time to read this, and I hope you enjoy learning and bonding with your child!