Science Experiment : Carbonate Gang

The main ingredient in egg shell is calcium carbonate (CaCO₃₎ - the same as that of chalk, limestone, cave stalactites, sea shells, coral, and pearls. The shell itself is about 95% CaCO₃ with the remaining 5% consisting of calcium phosphate and magnesium carbonate and soluble and insoluble proteins.

What Do I Need?

·         Egg

·         Coral

·         Vinegar

·         Clear glass (2)

What Do I Do?

1.    Pour vinegar into the glasses until it is three quarters full.

2.    Place a piece of coral and a raw egg into the vinegar separately.

3.    Observe what happens.

4.    Leave it for a few days.

Questions:

·         What is the similarity between the egg and coral?

·         How do we relate them to ocean acidification?

·         Will ocean acidification take place?

What’s Going On?

1.    Bubbles are seen enveloping the egg and coral as soon as it’s in contact with vinegar.  The bubbles are carbon dioxide gas, produced as the egg shell and coral dissolves. 

2.    After a while, we can see a layer of sedimentation in the glass with coral.  After 24 hours immersed in vinegar, the egg loses most of its shell leaving the fine white membrane that stores the egg yolk and egg white.

                    2 CH₃COOH + CaCO₃   -->  H₂O + CO₂ + Ca(CH₃COO) 
                               vinegar          calcium                                calcium acetate

                                             carbonate

3.  Shells serve as a protective structure for both marine and terrestrial organisms. Marine eco- systems that depend upon calcium carbonate to make shells can be impacted by changes in ocean pH due to increased carbon dioxide.

4.  In experimental conditions under very high levels of CO2, shells of clams, oysters, corals, snails and urchin shells dissolve. If these organisms are unable to build or repair shells, with increased acidification caused by industrial emissions, deforestation and other human activities, they will likely cease to exist in these environments. These results do not occur for all organisms.

5.  In experimental conditions, extreme increases in carbon dioxide result in crabs, lobsters, temperate sea urchins, limpets, and calcifying algae all building thicker shells with the more acidic conditions. Some organisms are able to adapt more rapidly than others and some will leave an environment if they cannot adapt.