Page 41 - Curriculum Visions Dynamic Book

Copper
alloy: a mixture of a metal and various other elements.
Tin
 A bronze bell in Fort Sutter, Sacramento, California, USA.
 Snail-eating utensils cast in pewter.
Bronze is an alloy of copper and tin. Up to 10% of tin is normally used. Bronze has been used for decorative metal objects and also for coins. It was one of the earliest metal alloys made, giving rise to the first metal-working age, known as the Bronze Age, over three thousand years ago. Bronze Age people, however, did not know about alloying metals but used copper ores that contained tin impurities.
Bronzes are important because they are strong, they do not wear away easily (when used, for example, in gear wheels), and they resist saltwater corrosion. The rule is, the more tin there is in the alloy, the harder and more brittle it becomes. Bronzes with up to one-twelfth tin are used mainly for sheets, wire and coins; those with one-eighth tin are used mainly for gears, bearings and ships in exposed locations. When bronze contains up to one-fifth tin, it is used for gear wheels; and with up to one-quarter tin, bronze is used to make bells.
Also... special bronzes
A wide range of specialised bronzes are used, each with its own distinctive properties. These are produced by alloying with more elements. Phosphor bronze, for example, is commonly used for bearings in machines or engines where shafts continually rotate. Phosphor bronze is made by adding one-third of 1% of phosphorus to the alloy.
Silicon bronze is a strong metal, used in places where there is a great danger of corrosion, such as a chemical works. This alloy contains up to 3% silicon.
Bronze
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