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Calcium carbonate has the chemical formula, CaCO 3 PowerPoint PPT Presentation


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Limestone. Limestone is a type of sedimentary rock that is mainly made up of a substance called calcium carbonate. Calcium carbonate has the chemical formula, CaCO 3. Because it has many uses and can be used to make other products, limestone is a valuable resource.

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Calcium carbonate has the chemical formula, CaCO 3

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Calcium carbonate has the chemical formula caco 3

Limestone

Limestone is a type of sedimentary rock that is mainly made up of a substance called calcium carbonate.

Calcium carbonate has the chemical formula,CaCO3

Because it has many uses and can be used to make other products, limestone is a valuable resource.


Calcium carbonate has the chemical formula caco 3

Basic properties of limestone

The appearance of limestone can vary tremendously.

Limestone is calcium carbonate and like any carbonate, it reacts with acids producing carbon dioxide gas.

Because it reacts with acids, it is sometimes added to lakes to remove acidity caused by acid rain.

Carbon dioxide turns limewater milky.

bubbles of CO2


Calcium carbonate has the chemical formula caco 3

Limestone, chalk and marble are all forms of calcium carbonateCaCO3.

Marble

Limestone

Chalk

Limestone is a sedimentary rock and most of it

(especially chalk) was formed from the remains of tiny sea creatures.

This process took millions of years.

Limestone and chalk often contain fossils.


Calcium carbonate has the chemical formula caco 3

Where is limestone found in the British Isles?

limestoneareas

There are also limestone cliffs on the coast in the Vale of Glamorgan


Calcium carbonate has the chemical formula caco 3

Sedimentary rocks at Llantwit Major in the Vale of Glamorgan

Layers of limestone and shale

fossils from rocks on left

prepared specimen – a Jurassic oyster (180 million years old!)

fossils in the fallen limestone blocks


Calcium carbonate has the chemical formula caco 3

More fossils found in limestone.

A Jurassic ammonite from

North Yorkshire.

180 million years old.

A Silurian gastropod (snail) from Shropshire.

400 million years old.


Calcium carbonate has the chemical formula caco 3

Important uses of limestone

1.

As a building material

Limestone has been used for thousands of years for buildings and roads.

However, since it is attacked by acids it is easily weathered and eroded.


Calcium carbonate has the chemical formula caco 3

2.

For making glass

Glass is made by heating a mixture of limestone , sand and sodium carbonate (soda).


Calcium carbonate has the chemical formula caco 3

3.

For making cement

Cement is made by heating together powdered limestone and clay in a rotary kiln.

Limestone and clay

Rotating kiln

Gas burners

Cement

Crusher


Calcium carbonate has the chemical formula caco 3

Cement

Mix with sand and water and chippings

concrete for buildings etc.

Mix with sand and water

mortar for joining bricks together


Calcium carbonate has the chemical formula caco 3

Summary – the uses of limestone

Buildings and roads

Mortar (cement + water + sand)

Cement (heat with clay)

Glass (heat with sand and sodium carbonate)

CaCO3

Neutralise acidic soils and lakes

Concrete (cement + sand + gravel + water)


Calcium carbonate has the chemical formula caco 3

Limestone Quarrying

The quarrying of limestone can have major effects on the environment.


Calcium carbonate has the chemical formula caco 3

Limestone quarrying provides the raw materials for making many important substances such as glass and cement etc. It also provides employment for people and benefits the local economy.

But what exactly are the disadvantages?


Calcium carbonate has the chemical formula caco 3

Limestone Quarrying – some disadvantages

An ‘eyesore’ in areas of the countryside

Noise from blasting

Loss of habitat for wildlife

Dust etc. from lorries


Calcium carbonate has the chemical formula caco 3

Heating limestone

The thermal decomposition of limestone

When limestone is strongly heated is begins to glow (limelight!)

It decomposes to form calcium oxide (quicklime) and carbon dioxide gas.

We can write a word equation:

calcium carbonate

calcium oxide + carbon dioxide

or a symbol equation:

CaCO3 CaO + CO2

This type of reaction, where a substance is broken down by heat is called a THERMAL DECOMPOSITION


Calcium carbonate has the chemical formula caco 3

Calcium oxide (quicklime) is produced industrially using a lime kiln

Kiln rotates to ensure that the limestone is mixed with the hot air

Air + carbon dioxide

Hot air in

Limestone in

Lime out

heat

calcium carbonate

calcium oxide + carbon dioxide

A thermal decomposition reaction

a lime kiln


Calcium carbonate has the chemical formula caco 3

Adding water to quicklime

‘slaking’ lime

When water is added to quicklime (calcium oxide), the reaction produces much heat and slaked lime (calciumhydroxide) is formed.

A reaction that produces heat is called an exothermic reaction.

We can write a word equation:

calcium oxide + water

calcium hydroxide

or in symbols

CaO + H2O Ca(OH)2

Calcium hydroxide solution is limewater which turns ‘milky’ with carbon dioxide.


Calcium carbonate has the chemical formula caco 3

Slaked lime (calcium hydroxide) also has uses:

  • to neutralise acidic soil

  • to make lime mortar (often used to restore old buildings


Calcium carbonate has the chemical formula caco 3

Heating other carbonates

A number of other carbonates are decomposed in the same way as calcium carbonate when heated e.g.

CuCO3 CuO + CO2

heat

copper carbonatecopper oxide + carbon dioxide

(green)

(black)

heat

zinc carbonate zinc oxide + carbon dioxide

(Zinc oxide is yellow when hot, white when cool)

ZnCO3 ZnO + CO2

Both these reactions are again examples of a thermal decomposition.


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