Limestone Deposit Experiment

by Lori Karjalahti
February 5, 2009, Takilma, OR

This week the Dome School students continued to test for CO2. Last week after adding CO2 with their breath to lime water the students labeled their glasses of limewater and set them aside where they would go undisturbed for 7 days.

This week Kelpie helped them continue the lime water activity and perform another carbon experiment.

Performing the Experiment

The students began by observing their glasses of limewater they created last week. Some of the students noticed that all the liquid had evaporated and all that was left was a crust in the glass, others saw that there was still some liquid and that where the limewater had been there was a crusty ring.

Kelpie explained that when Carbon Dioxide (CO2) in the air mixes with the limewater a "crust" is formed, this "crust" is Calcium Carbonate (CaCO3) a limestone deposit.

Kelpie first instructed the children to carefully pour out the water in their glasses.
Annabella pours vinegar into a cup with a limestone crust

Next they added vinegar up to the limestone crust and watched for 5 minuites to see what would happen.

The kids sat watching for what seemed like forever. Finally, one by one they saw bubbles.

The students enjoyed swirling the vinegar in their glasses until all the limestone crust had disappeared and the glass turned clear.

Kelpie explained that when the vinegar was added to the limestone a chemical reaction took place and that the bubbles they were seeing was CO2 being released back into the air.

Research Reports

After completing their experiment the students then moved on to write their reports. First we had a brief discussion reflecting back on Tom Seiwert's visit when they learned about the formation of limestone and caves.