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Useful Products from Rocks |
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Limestone
Limestone is a very useful type of sedimentary rock.
It is a naturally occurring form of calcium carbonate, CaCO3.
Limestone is used as a building material.
In powdered form, it can be added to lakes and soils to neutralise acidity, because it is a base.
When limestone is heated strongly in a kiln, it breaks down to quicklime (calcium oxide) and carbon dioxide.
calcium carbonate |
—› |
calcium oxide |
+ |
carbon dioxide |
(limestone) |
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(quicklime) |
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This type of reaction is called thermal decomposition. Other carbonates also undergo thermal decomposition.
Quicklime reacts with water to produce slaked lime (calcium hydroxide).
calcium oxide |
+ |
water |
—› |
calcium hydroxide |
(quicklime) |
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(slaked lime) |
Slaked lime is also used by farmers to neutralise acidic soils.
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Cement, Concrete and Glass
Cement is made by roasting powdered limestone with powdered clay in a rotary kiln.
When water is added to powdered cement, a series of chemical reactions take place to form a hard interlocking mass of crystals.
Concrete is made by mixing cement with water, sand and crushed rock.
A slow chemical reaction occurs which eventually forms hard, stone-like concrete that is used for building.
Reinforced concrete is made by allowing the concrete to set around steel rods. This makes it stronger.
Glass is made by heating a mixture of limestone, sand and soda (sodium carbonate).
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