4. Прочтите еще раз внимательно текст "Classification of metals". Постарайтесь ответить по-английски на вопросы, не заглядывая в текст

1) Into what groups may we divide metals according to their chemical purity?

2) What are a simple metals?

3) What is an alloy? What does it consist of?

4) Into what groups do we usually divide metals in modern industry?

5) How will you call metals consisting of iron combined with some other elements?

6) Into what groups may we divide ferrous metals?

7) What is the most important ferrous metal?

8) How are cast irons classified (into what groups)?

9) How are metals divided according to their density?

10) What are the densities of light metals (of heavy metals)?

11) What alkali and alkali earth metals do you know?

12) What is the lightest (heaviest) metal?

13) Into what two groups may non-ferrous metals be subdivided?

14) Can metals be classified according to their melting point?

15) What metals and alloys are called refractory? Are they easy to produce?

16) What are the low melting point metals?

17) What can you say about potassium and chromium?

18) What are a semimetals?

Самостоятельная работа студентов

5. Перепишите в свои словари все новые для Вас слова и словосочетания из урока 3. Выучите их к следующему занятию.

6. Переведите письменно следующие определительные группы из 2-х и 3-х слов (2-х и 3-х компонентные терминологические сочетания)

atomic energy; useful machines; the old friends; wide application; high strength; ancient Romans; the great scientist; bad ductility; the main characteristic; his Periodic table; the first scientific definition; its scientific significance; metallic luster; high electron conductivity; pure metal; physical properties; a high density; low melting point; a poor conductor; this good conductor; a basic oxide; these metallic oxides; the chemical properties; a non-metal; acidic oxide; the soluble oxide; a dilute acid; simple metals; the pure metal; old time; ferrous metals; a positive ion; the negative ion; a solid metal; the liquid metal; carbon steel; alloy steel; stainless steel; the alkali metals; the alkali earth metals; their industrial application; their chemical purity; modern industry; two main groups; their chemical composition; rare metals; precious metals; their melting point; a refractory metal; non-ferrous metals; poor corrosion resistance; hard metal; heavy metals; true metals; these light metals.

7. Прочтите самостоятельно дополнительные тексты и передайте их содержание на русском языке silver

Silver, like gold, as you know is one of the precious metals. It was first used for ornament and later for coins (монеты). Silver is a white shining metal. It is harder than gold and will, in time, tarnish (тускнеть) and lose its lustre. The use of silver for making mirrors (зеркала) is very interesting. The first metal mirrors were made of polished bronze. Later on, a mixture (смесь) of lead, silver and copper was used. There were no glass mirrors in Roman times, though the Romans knew how to make glass (стекло), but they did not know how to apply silver or tin to glass. Polished metal mirrors of silver, bronze came into common use only in the sixteenth century.

LEAD

Lead, probably, followed (сменить кого-либо, что-либо) silver as a useful metal. Sometimes it was mixed with bronze. The more common use of lead was for roofs, pipes, paints. After the invention of gunpowder (порох) lead served for several centuries for the bullets (пуля). We also use lead nowadays. It is used in making glass and especially paints.