Text e . Gases

As we have seen above, when a solid or a liquid is heated, there comes a time when the molecules have got enough energy to break away from the intermolecular attraction forces and become free. Now they can move in all directions and will continue to do so until stopped by a collision, and continue to move in another direction until the next collision takes place. This means that the gases have no fixed volume, they fill all the space that is available and there will be a continual bombardment of the walls of the container by the molecules of gas. Since many millions of molecules are continually carrying out this bombardment a considerable force is brought to bear on the walls, and the force per unit area is known as the pressure exerted by the gas.

Unit V. Polymeric materials.

I. Language.

Exercise 1. Read and memorize the words.

clothing - одяг, обшивка

durability – стiйкicть , тривалicть

fibre -волокно

wool –вовна , шерсть

coating – обшивка , покриття

leather - шкiра

adhesive – липкий , клейкий

fatty -жирний

to repair –лагодити , ремонтувати

resin – смола

to precipitate –осаджувати

starch – крохмаль

intricacy –складнiсть

Exercise 2 . Guess the meaning of the following international words :

structural , instrument , products , apparatus , alcohol , to dominate , polymer , organic ,protein , cellulose , corrosion , synthetic .

Exercise 3. Find the pairs of synonyms and remember them:

to provide, due to, lately, to supply, clothing , because of, recently, artificial, a lot of, use , principal, man-made, many, to learn, for example, to find out, for instance, various, coating , application , main , different.

Exercise 4. Find the pairs of antonyms and remember them:

natural, long, artificial, satisfactory , short, organic, involve, appear, modern, evolve, heavy, disappear, old, light, cheap, expensive , unsatisfactory , inorganic .

Exercise 5 . Define the part of speech of the words below paying attention their suffixes .

fundamentally , transportation , complexity , molecular , desirable , further , development , satisfactorily , durability , resistance , investigation , existence , structural , powerful , viscometer , incredibly , establishment , numerous , Ukrainian .

Exercise 6 . Translate the following word combinations .

man-made organic polymers , powerful physical instruments , electron microscope ,X-ray-diffraction apparatus , giant molecule , flexible chains , numerous polymeric materials .

II. Reading.

Exercise 7 . Read and translate text A “The nature of polymeric materials.”

Text A.

The nature of polymeric materials

Life depends fundamentally on organic polymers. These polymers provide not only food but also clothing, shelter and transportation.

Indeed nearly all 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, paints and so on. The organic polymers from which such things could be made include proteins, cellulose, starch, resins, and a few other classes of compounds.

Because of the complexity and fragility of their mole­cules, the natural organic polymers, although known and used for ages, defied attempts to analyse their molecular structure until very recently.

Modern methods of physical and chemical analyses have uncovered the principles that govern the properties of the natural polymers.

On the basis of the discovery involved a new industry of man-made organic polymers has appeared. 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 development.

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 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 other 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, alcohol 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, silk. The substances composing these materials couldn't be crystallized from solu­tion, 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, vis­cometer, 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 gasoline have molecular weights in the range of only about 50—500.

The giant molecules can be composed of a large number of repeating units, they being given the name "polymer" from the Greek words "poly" many and "meros" a part. Most poly­mers have the form of long, flexible chains. Having found out that, chemists began synthesizing 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.

Now it's quite clear that the production of synthetic polymers is very important.

Ukrainian scientists work hard at this problem. It is quite clear that Ukrainian science will continue to create new polymers and our industry and agriculture will receive cheap new mate­rials with valuable properties.