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LIME-STONE
What is Limestone? Limestone is made up of the shells of millennia old dead sea creatures. Layers of these built up over millions of years, and were squashed together until they formed limestone. This means it is a sedimentary rock.
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Types of Limestone There three different types of limestone: Chalk is a very soft form of limestone which
has had less pressure put on it whilst it was being formed. Marble is the hardest form of limestone, as it was subjected to lots of pressure when it was formed This is a metamorphic rock. Limestone is the third type and is formed at a medium pressure. http://www.frontdesk.co.in/forum/
Chemical Stuff Chalk, Limestone and Marble are different
forms of the same compound – calcium carbonate. Calcium carbonate is made from carbon, oxygen and calcium and has the formula CaCO3. Calcium carbonate is an insoluble chemical, and is also a base. (Bases neutralise acids).
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The chemistry of limestone The limestone cycle (next slide) shows how 3 very important chemicals can be made from limestone: Lime Slaked lime and Limewater
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Key
Limestone Cycle
Added to substance Taken away from substance
Calcium Hydroxide (AQ) Ca(OH) 2
Limestone CO2
CO2
H2O
Heat
Lime Water H2O
Calcium oxide (CaO)
Lime
Slaked Lime
H2O
Used to detect for the Calcium hydroxide presence of CO2. Turns cloudy if CO2 is bubbled Ca(OH)2 through it http://www.frontdesk.co.in/forum/
Uses of limestone Limestone also has many other uses: to make glass in the production of paper and iron as a building material to make cement and to neutralise acidic soils and lakes.
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Glass Glass is made by heating a mixture of sand,
limestone and soda (sodium carbonate) until it melts. When the mixture cools it comes out as glass. Glass is used for many everyday things such as windows, glasses and mirrors.
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Neutralisation Ordinary limestone, ground into a powder,
can be used to neutralise acidity in lakes and soils caused by acid rain. The calcium carbonate is a base (an insoluble alkali), and so can neutralise the the acid. Slaked lime works in the same way but is much faster.
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Cement ď Ž When limestone is heated with clay it forms
cement, a substance that sets gradually when it reacts with water. ď Ž Cement can be made into mortar by adding sand and water. Mortar is used to set the bricks in walls, as when it dries it acts as an adhesive between the bricks.
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Cement (cont) ď Ž Cement can also be made into concrete by
adding water, sand and small stones or gravel. ď Ž Concrete is used for all kinds of building work, including paths, walls and large buildings.
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Summary ď Ž Limestone (CaCO3) is formed from seashells
by a process that takes millions of years. ď Ž Limestone is used to make many things in
our everyday lives, such as glass, cement, paper and buildings.
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