) :
| 1) century 2) nature 3) machine 4) mechanism 5) metal 6) application 7) element 8) property 9) strength 10) plasticity 11) brittleness 12) ductility 13) rubber 14) characteristic 15) definition 16) substance 17) significance 18) heat 19) conductivity 20) engineering 21) compound 22) stone 23) alloy 24) luster | a) b) c) d) e) f) g) h) i) ; j) k) l) m) n) ; o) p) q) r) ; s) t) u) v) w) x) |
b) :
| 1) useful 2) old (= ancient) 3) rich 4) interesting 5) wide 6) high 7) plastic 8) strong 9) brittle 10) great 11) bad 12) main 13) scientific 14) metallic (= metal) 15) pure | a) b) c) d) e) f) g) h) i) , j) k) l) m) n) o) |
c) :
| 1) to serve man 2) to conquer nature 3) to create machines 4) to find wide application 5) to possess properties 6) to make metals so useful 7) to combine strength and plasticity 8) to exclude antimony and mercury from the list of metals 9) to discover the Periodic System 10) to give a scientific definition 11) to lose scientific significance 12) to comprise two main characteristics of metals 13) to consist of many elements 14) to be called alloys | a) b) c) d) e) () f) g) h) i) j) k) l) m) n) |
Read Text A and answer the following questions.
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A
METALS AND MEN
Fr 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.
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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 ( ) in 1763. wrote: Metals are light color bodies which can be forged ( , ). 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 luster, 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.
