3 Part One. The Predicate

The Properties of Solutions
It is difficult to give a definition which tells clcarly and briefly how solutions differ from mixtures and compounds, in spite of the fact that solutions are among the most familiar substances to be found in nature.

However, it is often true that the most common concepts We use are the most difficult to define precisely. A solution is a homogeneous substance that has, over ccrtain limits, a continuously variable composition. The word “homogeneous” sets a true solution apart from a mechanical mixture, for mixtures have macroscopic regions which have distinct and different composition and properties. The properties and composition of a solution are uniform, as long as the solution is not examined at the molecular level.

There are substances, however, not to be clcarly classified as solutions or mixtures. A solution of soap in water has a cloudy appcaiancc due to particles which consist of many soap molecules collected together. Such a substance has properties and composition which might be described as either inhomogcncous or homogeneous depending on die experiment to be done. Therefore, there is no sharp dividing line between mixtures and solutions.

The requirement that solutions have continuously variable composition distinguishes them from most compounds. However, many solid materials We commonly think of as compounds actually show variable composition.

Cuprous sulphide and ferrous oxide are examples of compounds which might also be thought of as solutions. No matter how carefully We made our definitions of solution, mixture, and compound, We must expect to find certain substances not to be uniquely classified as one of these. There is no reason to expect nature to be cooperative and producc only substances which are easily classified, and since this is the case, the most useful definitions are often the shortest, rather than the most exhaustive.
Words and Word-Combinations to Be Memorized

actually, appcarancc, brief, briefly, this is the case, certain, classify, clearly, continuously, depending on, distinct, examine, familiar, ferrous, for, homogeneous, level, as long as, mechanical, no matter, precisely, requirement, to set, uniform, variable

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

to give a definition, to tell clearly and briefly, in spite of tlic fact, it is often true, the most common concepts, over certain limits, as long as, a cloudy appcarancc, the experiment to be done, a sharp dividing line, no matter how carefully, since this is the ease

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

farq qiladi, eritmalarning xossalari, tabiatda topilishi mumkin bo'lgan moddalar, bir hil moddalarni, o'zgaruvchan tarkibni aniq belgilash, molekulyar darajada o'rganish, aniq tasniflash, tajribaga qarab, taxmin qilish uchun asos yo'q.

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

1. It is rather difficult to give ... definition o f ... solution. 2.... word “homogeneous'* sets ... true solution from ... mechanical mixture. 3— ferrous oxide is ... example o f ... compounds We may consider as ... solution. 4. ... most useful definitions are often ... shortest. 5. At ... molecular level... properties o f ... solutions are not examined well enough.

Ex. 8. Give synonyms for the following:

precisely, distinct, different, examine, however, due to, consist of, many, do, material, commonly, actually, show, also, since difficult, familiar, often, apart, different, short, most, certain, variable

Ex. 10. Translate the sentences into Uzbek.

1. Professor N was the first to prepare this kind of glass electrodcs in our laboratory. 2. They stayed at the laboratory till 8 in the evening, because they had a lot of work to do. 3. There are two points to discuss. 4. Tins is the condition for everybody to observe. 5. There are some rules never to be forgotten. 6. Students who study chemistry must Icam to do experiments. 7. Here is the room where chemicals are stored. 8. The need often arises in chemical researeh to measure die concentration of a solution with a high degree of precision. 9. A student about to begin an experiment must get his supervisor’s permission. 10. The substance to be dissolved is called die solute.11. There are a lot of problems for chemists to solve. 12. Acids are chemicalsto be used carefully. 13. Not the least of D. I Mendeleyev’s services to chemistry was his publication of the first text-book of chemistry to be based throughout on the periodic system of classification. 14. John Dalton was by no means the first to speculate about an atomic theory. 1 S. Lavoisier was the first to realize the importance of the balancc for chemical investigation. 16. D. I. Mendeleyev was the first Russian chemist to receive widespread recognition in the West during his lifetime. 17. The first clement of the series of noble gases to be discovered was argon. 18. Oxygen is frequently chosen as one of the first elements to be studied in chemistry. 19. The rise of temperature gives more opportunity for the molecules to react. 20. There is usually a limit to how much solute a given volume of solvent can hold at a given temperature. 21. Compounds have properties that differ from those of the constituent elements. 22. We are living at a time when chemistry is used almost everywhere. 23. The periodic law D. I. Mendeleyev discovered created a new era in the history of chemistry. 24. The question whether a particular gas is lighter or heavier than air can be easily solved. 25. The state of ap substance depends usually on die temperature and pressure it is subjected to. 26. The elements water is composed of are hydrogen and oxygen. 27. The first element We shall study in detail is oxygen. 28. It is recommended that water We use for drinking should be boiled. 29. It often happens that the necessary condition for the reaction to begin is the presence of a catalyst. 30. It is the usual laboratory practice that the potassium chlorate oxygen is to be produced from is placed in a vessel and heated.

Ex. 11. Translate the sentences into English without using a dictionary.

1. Eritmalar aralashmalardan qanday farq qiladi degan savolga har doim ham javob berish oson emas. 2. Tabiatda topilishi mumkin bo'lgan moddalar orasida ko'plab yechimlar mavjud. 3. Bir hil xususiyatli aralashmadan haqiqiy eritmani ajratib olishga imkon beradi. 4. Eritmalarning ba'zi xususiyatlarini faqat molekulyar darajada tushuntirish mumkin. 5. Tabiatda topilgan moddalarni har doim ham tasniflash oson deb o'ylashga asos yo'q.

Ex. 9. Give antonyms for the following:

1. Why is it difficult to give a definition of a solution? 2. Solutions are among the least known substances, aren't they? 3. What is usually considered as the main property of solutions? 4. In what way can you characterize a solution of soap in water? 5. Can one easily classify substances to be found in nature? 6. What definitions are the most useful?