Текст a metals and men

Fоr many centuries metals have served man helping him to conquer nature, to create useful machines and mechanisms.

The world of metals is rich and interesting. Among metals are the old friends of a man: Iron (Fe), Copper (Cu), Lead (Pb), Mercury (Hg), Gold (Au), Silver (Ag), Tin (Sn). At present out of 104 elements of the Mendeleyev's Periodic Table about 60 are metals. Metals have found wide application because they possess properties which made them so useful: for example, they combine high strength and plasticity. Some other materials, stone for example, possess strength, but are brittle. Rubber is highly plastic, but it is not strong.

Ancient Romans knew only 8 metals: gold, silver, copper, tin, lead, mercury, antimony, iron.

In 1763 the great scientist Lomonosov knew only 6 metals: gold, silver, copper, tin, lead, iron. He excluded antimony and mercury from the list of metals because of their bad ductility (forgeability) as ductility was considered to be the main characteristic of metals.

In 1869 Mendeleyev discovered his Periodic System, 50 metals being known by that time.

The first scientific definition of metal was given by M.V. Lomonosov in his book «The first foundation of metallurgy and mining» («Первые основания металлургии и рудных дел») in 1763. Не wrote: «Metals are light color bodies which can be forged» («Металлы – светлые тела, которые можно ковать»). This definition does not lose its scientific significance even now. It comprises the two main characteristics of metal: plasticity and metallic luster.

Besides, metals possess high electrical conductivity and heat conductivity.

In engineering metals are defined as substances possessing the following properties: metallic lustre, plasticity (ductility), high electrical and heat conductivity and high electron conductivity which rises with the decrease of temperature.

Not only pure metals (elements) possess these properties but also compounds consisting of many elements. Such substances are called alloys.

4. Найдите в тексте предложения, соответствующие данным

1) В течение многих столетий металлы служили человеку, помогая ему покорять природу, создавать полезные машины и механизмы.

2) Металлы нашли широкое применение, потому что они обладают свойствами, которые сделали их такими полезными.

3) Он (Ломоносов) исключил сурьму и ртуть из списка металлов из-за их плохой ковкости, так как считалось, что ковкость является характерной основной особенностью металлов.

4) В 1869 году Менделеев открыл свою Периодическую систему (элементов), причем к тому времени было известно 50 металлов.

5) В технике металлы определяются как вещества, обладающие следующими свойствами.

6) Не только чистые металлы (элементы) обладают этими свойствами, но также и соединения, состоящие из многих элементов.

5. Постарайтесь ответить по-английски на вопросы, не заглядывая в текст

1) Why have metals found such wide application?

2) What properties does stone possess?

3) What properties does rubber possess?

4) How many metals did ancient Romans know?

5) How many metals did Lomonosov know in 1763?

6) Why did Lomonosov exclude antimony and mercury from the list of metals?

7) When did Mendeleyev discover his Periodic System?

8) What was the first scientific definition of metals given by Lomonosov?

9) What two main characteristics does the first scientific definition comprise?

10) How are metals defined in engineering?

11) What is an alloy?