1. Earth History Limestone

2. The Basics
Limestone is a rock that forms at the bottom of oceans and contains calcium carbonate (calcite). Where does the calcium carbonate come from, and how does it get into the limestone?

3. Seawater Lab Investigation
In the lab, you showed that: Calcium Carbonate does not dissolve in water So, if Calcium Carbonate forms in the sea it will sink to the bottom where it can eventually turn into rock.

4. Ways to Get Calcium Carbonate
Animals combine calcium, carbon, and oxygen to make calcium carbonate shells (that is why the seashell and oyster shell fizzed).
Carbon dioxide exhaled by marine life combines with calcium to make calcium carbonate (this happened in your cups)

5. Extra Chemistry (for those interested)
Water – H2O Calcium hydroxide – Ca(OH)2 (aq) Calcium carbonate – CaCO3 (aq) Ca H + C + 2O  CaCO3(s) + H2O(l)