Science Experiment : Ocean Acidification

Does an excessive amount of carbon dioxide gas dissolved in our oceans cause it to be acidic? The experiment below demonstrates what happens to small amounts of water when carbon dioxide gas reacts with it.

What Do I Need?

·         Red cabbage juice

·         350 ml (or smaller) plastic bottle

·         Panadol Soluble®

·         Water

·         Balloon

What Do I Do?

How to prepare red cabbage juice (Acid-Base Indicator)

1.  Clean and tear a few leaves of the red cabbage into small pieces & put it into a medium sized bowl.

2.  Pour hot water over the torn red cabbage leaves & leave it for about 15 minutes.  The water will turn purplish.

3.   When the juice has cooled, begin the experiment.

The Experiment

1.   Add a few drops of red cabbage juice into a bottle with 50 ml of water.

2.  Add two tablets of Panadol Soluble® into the mixture and quickly cover the mouth of the bottle with a balloon.

3.  Observe what happens to the mixture and balloon.

Questions:

·   What does the colour change mean (when the tablets were dropped into the mixture)?

·   How do we relate this chemical change to ocean and marine life?

What’s Going On?

1.  The water changes from blue to light pink as the tablets bubble and disappear.

2. Panadol Soluble® contains sodium bicarbonate, sorbitol powder (E420), saccharin sodium, sodium lauryl sulphate, citric acid, sodium carbonate, polyvidone and dimethicone.

3.  In the effervescent action of Panadol Soluble®, the baking soda (sodium bicarbonate) and citric acid are active.
                
             C₆H₈O_{7 +} 3 NaHCO₃     -->   3H₂O +      3CO₂        + Na₃C₆H₅O
          Citric acid  baking soda           water   carbon dioxide  sodium citrate

4.  As the tablets dissolve in water, the base (bicarbonate) and the acid (citric acid) react vigorously producing carbon dioxide gas.

Ocean Acidification

1.  Ocean acidification is a consequence of rising global carbon dioxide levels that is predicted to have serious consequences for ecosystems, including corals. 

2.  Rising CO₂ levels upset the balance of carbonate ions in seawater, making it difficult for some organisms, which have shells composed of the mineral calcium carbonate, to form their shells. 

3.  Many of the organisms that are affected, and are predicted to be affected, are critical for ecosystem health.