1. Buffering Capacity: Seawater CO 2 Chemistry Scripps Classroom Connectionhttp://earthref/SCC

2. Sand Dissolution Demo Materials Needed Calcium Carbonate Sand Two 100 mL beakers Distilled water Seawater pH Indicator (probe or dye) Stir plate & bars OR Spoon Scripps Classroom Connection http://earthref/SCC

3. Where does sand come from? Riverine Runoff Weathering of Rocks Calcified parts of marine species Corals Foraminifera Scripps Classroom Connection http://earthref/SCC

4. Chemistry of Sand Scripps Classroom Connection http://earthref/SCC CaCO 3

5. CaCO 3 Minerals Calcite - rhombohedral Aragonite - orthorhombic Mg-Calcite – Mg 2+ replaces >4% of Ca 2+ in calcite Scripps Classroom Connection http://earthref/SCC

6. Seawater Buffering Lab Materials Needed (per group) Two 50 mL beakers 1 beaker will have distilled water (DIW) 1 beaker will have seawater (SW) Universal Indicator HCl (strong acid) NaOH (strong base) Droppers Goggles (1 pair per student) Scripps Classroom Connection http://earthref/SCC

7. Relation of carbonate chemistry and pH Scripps Classroom Connection http://earthref/SCC

8. Seawater Buffering Capacity Alkalinity (TA or A T ) = excess bases over acids Scripps Classroom Connection http://earthref/SCC

9. Modeling Seawater CO 2 Chemistry Scripps Classroom Connection http://earthref/SCC CO 2 + H 2 O ↔ H 2 CO 3  HCO 3 - + H + CO 3 2- + 2H + 

10. Modeling Seawater CO 2 Chemistry Scripps Classroom Connection http://earthref/SCC COO CO 2 1. Dissolves in the ocean OHH H2OH2O COOOH HCO 3 - 1. Reacts with water to form bicarbonate ion and hydrogen ion H+H+ COOO H+H+ 3. Most of that hydrogen ion reacts with carbonate ion to form more bicarbonate COOOH HCO 3 - CO 3 2-

11. The Need to Breathe Students hold breath as long as they can They should have felt the urge to take another breath This urge is due to increase of CO 2 beyond buffering capacity. Scripps Classroom Connection http://earthref/SCC

12. Another Buffer: Blood

13. Conclusions Buffers combat pH change CO 2 chemistry buffers pH Seawater is a buffer Blood is a buffer Scripps Classroom Connection http://earthref/SCC