Environmental Learning Natural Play Pure Science

Rocks Rock! Reuse a jar for 3 Easy Earth Science Experiments

Rocks hold stories.

I am pretty sure that I fell in love with geology while climbing the rock on the shores of Lake Superior at the age of, well, whenever I could leap!  What I did not know then is that the slabs of dark gray rock along the shoreline from Duluth northeast bound are basalt from a volcanic rift in earth’s crust 1.1 billion years ago.  Considering earth is estimated to be 4.6 billion years old, that’s not too long ago.  In college I trekked to Italy to study volcanoes with new rocks.  With some geology club friends we made a side trip to Austria.  At an Austrian university we met some professors studying rock cores that were pulled from our very own Duluth complex rock formations.  Talk about stories in the rocks!

Bottling up lava just is not going to happen, but here are three earth science experiments that can be done using kitchen chemicals and some natural materials from where you live.  The experiments pair up nicely with some storybooks, family trip pictures, and/or reference materials about the rock cycle.  The geosphere, or rock cycle, is made up of the rock types igneous, metamorphic, and sedimentary; along with the processes that change the rocks from one type to the other such as weathering, erosion, heat, pressure, volcanic eruption, cementation, deposition and more.

Jar #1:  Settle down sediments! 

Depending upon the size of the jar you are using, you’ll need about a handful or two of mixed sand.  Playground sand works nicely.  Make sure that there are sediments, or pieces of rock, of all sizes.  You may want to through in a few extra pebbles.  Put the sand in the jar then fill the jar three-fourths of the way full with water.  Cover tightly.  Shake.  Let it sit…for days!  Watch how the largest pieces settle out first followed by the smaller grains just like the rivers, streams, lakes and glacial lakes from 100,000-10,000 years ago in Minnesota.  Eventually even the brown dust will settle out to form a thin layer on top of the pebbles and sand grains.  It is this finely ground “rock powder” that forms clay when there is enough of it.

Jar #2:  Eggsellent cave formation…

Fill a jar half full with vinegar then add a raw egg and tightly cover the jar.  Do NOT shake.  Check it every day for a week or so and watch what happens!

When water seeps through the earth, called percolation, it dissolves minerals.  In some cases the water can become mildly acidic.  Acids dissolve limestone.  Just like limestone (mainly calcium carbonate) contains calcium so do eggshells.  Just like the vinegar slowly reacts with the eggshell, acidic groundwater reacts with limestone underground to form caves.

Jar #3:  Crystals are patterns of atoms or compounds.

A crystal is a repeating pattern of atoms or molecules.  Table salt, also known as the mineral halite, is a pattern of sodium connected to chloride connected to sodium connected to chloride and so forth in all directions to forma cubic crystal structure.  When growing crystals of sugar with sucrose molecules in a repeating pattern is called rock candy.

To make rock candy you will need to “saturate” a solution, or dissolve as much sugar into the water as you can.  Since hot water dissolves more solids you should start by boiling enough water to fill your jar.  Once it is boiling stir the liquid constantly and dissolve as much sugar into it as you can.  A ratio of 3 parts sugar to 1 part water is about right.  You may also add a few drops of food coloring for effect.

The crystals need a “seed” that starts the pattern of growth.  The seed could be a toothpick, piece of candy, or even a knot that hangs in the middle of the saturated solution without touching the sides.   A clean piece of string and a coffee stirrer or popsicle stick work nicely.  Cool the sugar liquid to just less than room temperature then drop in your string with “seed”, cover, and wait.

Play. Learn. Love.

November 2013