Formation of Calcium Carbonate

1. Formation of Calcium Carbonate Investigation 5: Limestone Earth History Grade 6

2. Quick Write • In your ISN on page 74, titled “Limestone Fizz Quick Write”, please respond to the following question: • How do you think limestone forms? What process of sedimentation might produce a rock that fizzes with dilute acid?

3. Fizzing of Limestone • Limestone fizzes in acid because they contain calcite. • Calcite is one form of calcium carbonate. • The fizzing is CO2 (Carbon Dioxide) being releases.

4. Think About This… • Scientists want to know… • “Where does calcium carbonate come from, and how does it get into the limestone?”

5. Formation of Limestone • Calcium carbonate does not dissolve in water (H2O). • If calcium carbonate forms in the sea or falls into the sea, it will sink to the bottom forming a layer. • The layer turns to rock and the rock is limestone.

6. Where Does Calcium Carbonate Come From? • Calcium Carbonate forms in the sea in two main ways:

7. Where Does Calcium Carbonate Come From? • Type1: • Some animals use calcium to make their bones, shells, and scales. • The calcium in shells combines with carbon and oxygen to make CaCO3 (calcium carbonate). • When the animal dies, the calcium settles to the bottom and can be incorporated into the forming rock. • Example: Oyster shells can be a main component of limestone.

8. Where Does Calcium Carbonate Come From? • Type 2: • Calcium carbonate also forms when CO2 (carbon dioxide), exhaled by organisms living in the sea, reacts with calcium in the water. • Calcium carbonate forms right in the water and precipitates to the bottom. • Example: the reside at the bottom of our cups.

9. Calcium Carbonate Chemical Equation • Ca(OH)2 + CO2 CaCO3 H20