3 Part One. The Predicate

Factors Affecting the Boiling Point
The temperature at which a liquid boils, is dependent not only upon the nature of the liquid itself, but also upon the pressure prevailing at the time the boiling point is determined. An increase in the atmospheric pressure causes a rise in the boiling point of a liquid; a decrease results in a lowering of the boiling point.

Each individual substance capable of existing in the liquid state has its own definite boiling point. Consequently, this property is used for identifying or characterizing a substance in the same way that density and other physical properties are employed.

Inasmuch as the boiling point of a substance is affected by changes in pressure, it has been found necessary to set up a standard pressureat which all boiling points can be compared. A pressure of 760 mm Hg has been selected as the standard. Thus, if the boiling point of water is given as 100°C, the measurement is understood to have been made at a pressure of 760 mm Hg. Nevertheless, il is quite true to say that the boiling temperature of water is 70°C at a pressure of 233.8 mm Hg; it is also correct to say that carbon tetrachloride boils at a temperature of 70°C, but in this case the pressure is 620 mm Hg. Boiling temperature should not therefore be used for distinguishing one substance from another unless the values used have been determined at the same pressure. Unless otherwise stated*, a boiling point value is understood to be the temperature at which a substance boils under a pressure of 760 mm Hg.

One atmosphere(standard atmospheric pressure) is equal to 101.325 kNm^-2:. It is not an approved SI (International System) unit of pressure, but it is especially important in chemistry because many properties of substances have been measured and recorded at 1-atm pressure. An approved SI unit of pressure is the pascal(1 Pa = 1 H/m²).

Another unit of pressure that has been much used in the past is the torr,which is the height in millimetres of a column of mercury that balances the pressure. The symbol mmHg is sometimes used for torr. The name of the unit is taken from the name of the Italian physicist Evangelista Torricelli (1609-1647), known for having invented the mercury barometer. One atmosphere is equal to 760 torr.
Words and Word-Combinations to Be Memorized

approve, balance, boiling point, capable, consequently, decrease, be dependent upon, employ, height, invent, lower, otherwise, record, select, set up, therefore, at the time, unless

Ex. 5. Give the Uzbek equivalents for the following:

be dependent on (upon), determine the boiling point, exist in the liquid state, consequently, in the same way, be afTcetcd by, set up, nevertheless, distinguish one substance from another, unless, be equal to, unit of pressure, be recorded at 1 -atm pressure, invent a barometer

Ex. 6. Give the English equivalents for the following:

ta'sir qiladi, suyuqlikning o'ziga ta'sir qiladi, qaynab turgan joyning ko'payishiga olib keladi, har bir alohida moddaga, o'z qaynash haroratiga ega bo'ladi, taqqoslang, me'yor sifatida tanlang, o'lchovlarni o'tkazadi, to'g'ri, atmosfera bosimi, italyan fizigi, simob barometri

Ex. 7. Fill in the blanks with prepositions where necessary.

1. The boiling point... a liquid is dependent... the nature of the liquid itself and the pressure. 2. A change... the atmospheric pressure results... a changing... the boiling point. 3. There was a need ... set... a standardpressure. 4. Usually measurements are made... 1-atm pressure. 5. Standard pressure is taken to b e ... a pressure... 760 mm. 6. Boiling points should be used ... distinguishing one substance ... another only ... the same pressure. 7. Another unit ... pressure is the torr. 8. One atmosphere is equal... 760 mm.

Ex. 8. Translate the sentences into Russian, paying attention to the constructions to do and to have something done.

1. The student translated an English articlc. 2. The student had an English articlc translated. 3. The student had translated an English articlc yesterday by 5 o’clock. 4. She sent the letter to her mother. 5. She had her letter sent two days ago. 6. She typed the paper. 7. She had the paper typed for her. 8. Each chemical element has been given its own name. 9. Each chemical clement has its own name given to it. 10. Each chemical element has its own name.

Ex. 9. Translate the sentences into Uzbek.

1. He likes reading. 2. He avoids making complex calculations. 3. There is no need doing it at once. 4. The teacher suggested going on an excursion.5. Don’t use this apparatus, it wants repairing. 6. Excuse my being late.7. Now I am very careful in the laboratory, 1 can’t forget my having burnt my left hand with an acid. 8. They were sorry for having missed the last lecture. 9. The student denied the laboratory assistant having helped him with the experiment 10.1 don’t mind my sister’s taking my notes. 11. Under ordinary conditions the precipitate may fail to begin forming. 12. It is neccssary to practise identifying the constituent elements of a sample. 13. The fundamental chemical laws are worth studying. 14. The conference is going to be very interesting, we cannot help going there. IS. Mendeleyev’s wide interests in various sciences did not prevent him from taking part in social life. 16. Alkali metals are capable of reacting with a number of the non- metals, forming binary products, c. g., chlorides, bromides, etc. 17. Before working in the laboratory, students must Icam what measures should be taken against being poisoned by chemicals. 18. Everybody knows of D. I. Mendeleyev’s having organized the Chamber of Weights and Measures in Russia. 19. Alchemists succccdcd in both preparing a number of new elements and inventing useful pieces of apparatus. 20. S. V. Lebedev succeeded in making the first synthetic rubber in the world.

Ex. 10. Translate the sentences into English.

1. Moddani qaynab ketishiga ta'sir qiluvchi omillarni bilish kerak. 2. Ushbu omillarning asosiysi: moddaning o'zi, harorat va bosim. 3. Atosfera bosimining oshishi, ma'lumki, suyuqlikning qaynash nuqtasini ortishiga olib keladi. 4. Taqqoslanadigan natijalarni olish uchun o'lchovlar bir xil bosimda olinishi kerak. 5. 760 mm simob ustuni 1 atmosfera standart bosimi sifatida qabul qilinadi. 6. Ilgari ishlatilgan va ba'zida hozir ishlatiladigan yana bir bosim birligi - torr.

7. 1 torr ¹/₇₆₀ atmosferaga teng, nomi italyan fizigi E. Torrielli nomidan kelib chiqqan.
Ex. 11. Answer the following questions:

1. What factors is the boiling point of a liquid dependent on? 2. How does the atmospheric pressure affect the boiling point? 3. What was the need of setting up a standard pressure? 4. What pressure was selected as a standard? 5. In what way can the boiling point be used in comparing the substances? 6. What do We mean if the pressure is not pointed out in the description of an experiment? 7. What other units o f pressure do you know?