Свойства хлора

PROPERTIES OF CHLORINE

Теоретическая часть

В рамках предлагаемого практического занятия студенты работают с текстом практического занятия 21. Целью данного практического задания является закрепление лексики, предложенной в теоретической части практического занятия 21, развитие навыков работы со словарем, навыков перевода и составления монологического высказывания по теме.

Задания

Задание 1. Выберите соответствующие слова или группы слов и заполните пропуски, переведите предложения на русский язык:

1. Electrons are said ... (to be neutral, to be positively charged, to be negatively charged). 2. The hydrogen atom is stated ... (to contain a neutron, to contain a proton and a neutron, to contain one neutron and one proton). 3. Chlorine is never found ... (in a combined state,, in a free state). 4. Experiments showed chlorine ... (to be soluble, to be insoluble, to be only slightly soluble). 5. The positively charged atom of hydrogen is ... (a proton, a neutron, an electron). 6. Free sili­con is ... (widely used, not used, has few uses).

Задание 2. Из двух простых предложений составьте одно с объектным ин­финитивным оборотом:

1. They watched the reaction. The reaction proceeded violently. 2. We know chlorine. Chlorine is a typical non-metal. 3. M. Curie found the atomic weight of radium. The atomic weight of radium is 226. 4. We know amorphous silicon. Amorphous silicon consists of very small crystalls. 5. We observed that reaction. That reaction was accelerated by a catalyst. 6. The spectroscope shows the outer atmos­phere of the sun. The outer atmosphere of the sun consists largely of hydrogen.

Задание 3. Переведите следующие группы слов на русский язык:

most abundant natural compound, a vigorous oxidizing agent, poisonous soluble barium salts, a concentrated solution of hydrogen peroxide, the escaping transparent odourless gas, various widely distributed substances unaffected by oxygen

Задание 4. Дайте три основные формы следующих глаголов: to find, to show, to know, to do, to play.

Задание 5. Перескажите текст.

Практическое занятие 22

Полимеры

POLYMERS

Теоретическая часть

Данный лексический материал предназначен для того, чтобы студенты усвоили базовые термины, с которыми они сталкиваются при чтении текстов по специальности. Работа с представленным ниже текстом направлена на развитие навыков просмотрового чтения.

Задания

Задание 1. Выучите следующие слова и словосочетания:

to depend – зависеть

indeed – действительно

to supply – снабжать, поставлять

leather – кожа

rubber – резина

paint – краска

starch – крахмал

resin – смола

compound – соединение

to govern – управлять

fibre – волокно

coating – покрытие

adhesive – связывающее вещество; клеящий материал

to possess – обладать

weight – вес

resistant – сопротивляющийся, стойкий, прочный

solvent – растворитель

moisture – влага, влажность

to compete – соревноваться

ancient - древний

Задание 2. Прочитайте текст (6 – 8 минут) и сообщите о проблеме, которая в нем рассматривается.

POLYMERS

Life depends fundamentally on organic polymers. If it were not so, we wouldn't have food, clothing, shelter and transportation.

Indeed, nearly all of the material needs of man could be supplied by natural organic products. The list of these materials and things made of them might be very long: wood, fur, leather, wool, cotton, silk, rubber, oils, paper, paint and so on. The organic polymers which these things are made from include: proteins, cellulose, starch, resins, and a few other classes of compounds.

There would be no industry of man-made organic polymers, were it not for modern methods of physical and chemical analyses which un­covered the principles that govern the properties of the natural polymers. One could list the principal products such as fibres, synthetic rubbers, coatings, adhesives and a lot of materials called "plastics". Plastics and synthetic coating are already in common use. It is desirable that they should be used on a large scale, and get further developed.

Synthetic polymers now available already possess several of the properties required in a structural material. They are light in weight, easily transported, easily repaired, highly resistant to corrosion and solvents, and satisfactorily resistant to moisture. It would be necessary to add that they have long-lived durability and resistance to high tem­peratures. A very important question could arise over whether synthet­ic polymers could be made inexpensive enough to compete with the structural materials such as metals and ceramics. The answer could be — "yes".

It might seem odd that man came rather late to the investigation of organic polymers as the principal means of supporting life. The natu­ral polymers such as proteins, cellulose and others dominated his ex­istence and even in ancient times people used these materials.

Yet as late as the end of the 19th century polymer chemistry got lit­tle attention. Chemists attacked sugar, glycerol, fatty acids and other ordinary organic compounds — dissolving, precipitating, crystallizing and dis­tilling them to learn what these substances were composed of.

But only feeble efforts were made to investigate such common ma­terials as wood, starch, wool, and silk. The substances composing these materials couldn't be crystallized from solutions, nor could they be isolated by distillation.

It was only in the 20th century that the scientists began thorough investigation of these materials. Having used some powerful physical instruments, an electron microscope, viscosimeter, X-ray diffraction apparatus, they could have revealed the polymers in all their intricacy. Their molecules were incredibly large, the molecular weights running as high as millions of units, whereas simple organic substances such as, for instance, sugar and gasolene have molecular weights in the range of only about 50-500.

Giant molecules can be composed of a large number of repeating units, they being given the name "polymer" from the Greek word poly (many) and mews (a part). Many polymers have the form of long, flexible chains. If the chemists had not found that out, they wouldn't have been able to synthesize artificial polymers. This has led to the es­tablishment of industries producing synthetic fibres and numerous polymeric materials, many of which were less expensive and superior in various ways to the natural materials.

Задание 3. Выпишите и выучите незнакомые слова из последних четырех абзацев текста.

Задание 4. Внимательно прочитайте текст и ответьте на следующие вопросы:

1. What does the life depend on?

2. Why does life depend upon organic compounds?

3. What is the list of materials needed for life?

4. What do organic polymers include?

5. What have modern methods of physical and chemical analyses un­ covered?

6. What products appeared on the basis of the discovery of polymers?

7. What properties do synthetic polymers possess?

8. Did people use natural polymers in ancient times?

9. What were those polymers?

10. When did scientists begin thorough investigation of natural organic polymers?

10. What have they found out about polymers?

10. What are the molecules of polymers composed of?

Практическое занятие 23