Formation of Formation of Calcium Calcium

CarbonateCarbonateInvestigation 5: LimestoneInvestigation 5: Limestone

Earth HistoryEarth History

Grade 6Grade 6

Quick WriteQuick Write

In your ISN on page 74, titled In your ISN on page 74, titled “Limestone Fizz Quick Write”, please “Limestone Fizz Quick Write”, please respond to the following question:respond to the following question: How do you think limestone How do you think limestone

forms? What process of forms? What process of sedimentation might produce sedimentation might produce a rock that fizzes with dilute a rock that fizzes with dilute acid?acid?

Fizzing of LimestoneFizzing of Limestone

Limestone fizzes in acid because Limestone fizzes in acid because they contain calcite. they contain calcite.

Calcite is one form of calcium Calcite is one form of calcium carbonate. carbonate.

The fizzing is COThe fizzing is CO22 (Carbon Dioxide) (Carbon Dioxide) being releases. being releases.

Think About This…Think About This…

Scientists want to know… Scientists want to know…

““Where does calcium Where does calcium carbonate come from, and carbonate come from, and how does it get into the how does it get into the limestone?”limestone?”

Formation of LimestoneFormation of Limestone

Calcium carbonate does Calcium carbonate does notnot dissolve dissolve in water (Hin water (H22O).O).

If calcium carbonate forms in the If calcium carbonate forms in the sea or falls into the sea, it will sink sea or falls into the sea, it will sink to the bottom forming a layer. to the bottom forming a layer.

The layer turns to rock and the rock The layer turns to rock and the rock is limestone. is limestone.

Where Does Calcium Where Does Calcium Carbonate Come From?Carbonate Come From?

Calcium Carbonate Calcium Carbonate forms in the sea in two forms in the sea in two main ways:main ways:

Where Does Calcium Where Does Calcium Carbonate Come From?Carbonate Come From? Type1Type1: :

Some animals use calcium to make their Some animals use calcium to make their bones, shells, and scales. bones, shells, and scales.

The calcium in shells combines with carbon The calcium in shells combines with carbon and oxygen to make CaCOand oxygen to make CaCO33 (calcium (calcium carbonate). carbonate).

When the animal dies, the calcium settles to When the animal dies, the calcium settles to the bottom and can be incorporated into the the bottom and can be incorporated into the forming rock.forming rock.

Example: Oyster shells can be a main component of Example: Oyster shells can be a main component of limestone.limestone.

Where Does Calcium Where Does Calcium Carbonate Come From?Carbonate Come From?

Type 2Type 2:: Calcium carbonate also forms when COCalcium carbonate also forms when CO2 2

(carbon dioxide), exhaled by organisms (carbon dioxide), exhaled by organisms living in the sea, reacts with calcium in living in the sea, reacts with calcium in the water.the water.

Calcium carbonate forms right in the Calcium carbonate forms right in the water and precipitates to the bottom. water and precipitates to the bottom.

Example: the reside at the bottom of Example: the reside at the bottom of our cups.our cups.

Calcium Carbonate Calcium Carbonate Chemical EquationChemical Equation

Ca(OH)Ca(OH)2 2 + CO+ CO2 2 CaCO CaCO33 H H2200