Science, color, & fun: Crystals & effervescing "rocks"

We’re trying to do more activities with Ezra during the evenings and weekends, and during this past week, Garry and I found a couple science activities related to his preschool’s current theme: color.

Garry and Ezra made crystals, which was the monthly “challenge” for Dinosaur Train Nature Trackers. I posted a photo of their crystals on our Postilius Facebook page. Take a look at them and like our page while you’re there (a friendly wink and a nudge). 

I found an activity that was really simple and fun too. Basically, a little water is mixed with baking soda along with some food coloring (optional) to make a paste. The mixture is dried a few hours or overnight to make “rocks.” In the morning, a stream of vinegar is poured over the rocks. The baking soda reacts with the vinegar to make carbon dioxide, which causes the "rocks" to effervesce.

I can see how parents get excited about homeschooling. There is so much science underlying one simple, little demonstration, and I thought it was fun to share with Ezra. I told Ezra we were doing a chemical reaction with an acid (vinegar, which is weak acetic acid) and a base (baking soda, sodium bicarbonate) that would make bubbles (carbon dioxide).

This demonstration can easily be repeated as children age, sequentially introducing scientific terms and concepts such as chemical equations, formulas and structures, concepts of pH and the neutralization of acids and bases – pH indicator strips are always fun to use! The production of CO2 can be empirically demonstrated with a flame since in a small area around the effervescing rocks there should be a local environment devoid of oxygen (anaerobic), which will extinguish the flame. This demonstration can be repeated with other similar substances, such as chalk and limestone (both calcium carbonate), which will also effervesce carbon dioxide in the presence of vinegar and other weak acids. Eventually, these demonstrations can be linked with geochemistry and erosion through karst topography (geographically relevant in Southern Indiana), which arises from the erosion of limestone in the presence of weakly acidic water causing sinkholes in the landscape. The possibilities are seemingly endless!

Ezra, of course, mainly liked the food coloring, bubbles and rainbow soup. He liked it well enough that he wants "to make more rocks tomorrow.”