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SILVER

People have always loved silver (Ag) jewelry, containers, and other objects. Museums have beautiful silver objects made in Egypt in 4000 B.C. Persia and other Asian countries have made beautiful silver objects for centuries. The Romans learned from them and they greatly advanced the art and science of working with silver. Spanish explorers found that the Indians in Central and South America knew how to make silver objects 

Silver is one of the most valuable metals in the world. It is valuable for four principal reasons. There isn't very much of it compared with most metals. It is a beautiful white, shiny color. It is easy to work with, so people can make many things from it. The oxygen in the air does not cause silver to rust or oxidize

The value of silver has often led to the destruction of silver objects. People steal silver, especially during wars. Governments have melted it down to pay for wars. People sell it to pay for the necessities of life during bad times

Silver is widely distributed throughout the world, but in small amounts. The leading producer is Mexico. The world's largest silver mine is in Hidalgo, Mexico. Other important producers are the United States, Canada, Peru, The Soviet Union, and Australia. There are other smaller mines in many countries

Only gold is easier to work than silver. Silver can be beaten into a sheet less than 0.00025 millimeters thick. It is too soft to use by itself for jewelry or coins, so it is mixed with copper ( Cu ) . This increases the hardness, but it does not change the color

Governments have made silver coins for centuries. This has always been its main use. Jewelry, dishes, and other containers have also been important uses of silver. Silver on the back of glass changes the glass into a mirror.

Today silver is also used in chemical and electrical engineering because electricity travels well through it, and it doesn't rust. Silver is used in airplanes and train engines. It is used in film and even in some medicine. In fact, industry uses more silver than mines can produce. There has been a worldwide shortage since the 1960s

Metals are very important to a society. Each time people discovered a new metal or invented new ways to use metals they already had, their society advanced. Modern society could not exist without metals

Silver is a very special metal. It has many uses for people in the simplest and the most complex societies. It is also very beautiful and has enabled people to make objects that have lasted for hundreds of years. Today we can enjoy modern silver objects and things made thousands of years ago

Source : Concepts and Comments

دسته ها : English Readings
شنبه بیستم 12 1390 20:45
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