THE WONDER METALS

Date: 2015-10-07; view: 894.

The study of metals began in the Middle Ages when scientists searched for a technique “to convert” base metals like lead to gold. They never succeeded in making gold but at least by experimenting with metals (in contrast to ancient Greeks who only speculated about them), they made many discoveries.

All but 20 of the over of 100 elements identified to date are metals but only 7 of these are common in the Earth's crust. One can't find iron, which is the most widely used metal, in the free state (not combined with other metals) and must extract iron from naturally occurring compounds (ores) such as hematite, magnetite, and pyrite. The beautiful colors of rocks are due almost entirely to these iron compounds. In fact, the color of iron pyrite is very similar to the color of gold. Iron is very strongly magnetic, and the fact that the Earth is a magnet itself tipped scientists off to the fact that iron is a major component of the Earth's core, or center.

Pure iron is a relatively soft, silvery metal that is very active chemically (that is, it combines with oxygen to corrode or form rust). It often combines with other elements or compounds to form alloys such as steel or stainless steel or cast iron, which are more durable and rust resistant than pure iron.

Aluminum is the most abundant metal, but people didn't use it until a century ago because it's so active chemically and it's difficult to extract it. Like iron it's soft but in contrast to iron and steel, aluminum is very light and very resistant to corrosion. These qualities make it useful for airplanes, trains, automobiles, rockets and house siding.

In the space age the extraordinary properties of titanium have made it the new wonder metal. Lighter and stronger than steel, it is more resistant to corrosion and able to withstand heat.

The remaining major metals are sodium, potassium, and calcium, all too active chemically (they react violently with water) to be used in construction.

13. Agree or disagree with the following statements:

a) The study of metals began in the Ancient Greece.

b) In the Middle Ages many scientists searched for a technique “to convert” base metals like lead to gold.

c) People didn't use pure iron it until a century ago because pure iron is active chemically and it's difficult to extract it.

d) The beautiful colors of rocks are due almost entirely to hematite, magnetite, and pyrite which are iron compounds.

f) Aluminum is a absolutely soft metal that isn't active chemically.

g) Though aluminum is the most abundant metal, it was not used until a century ago.

h) Steel and stainless steel are types of alloys.

i) In the age of space flights titanium has become the new wonder metal.

j) Steel or cast iron aren't as durable and rust resistant as pure iron.

l) Sodium, potassium, and calcium are too active chemically as they react violently with water.

14. Retell the text “The Wonder Metals.”