mixtures. A solution of soap in water has a cloudy appcaiancc due to particles
which consist of many soap molcculcs collected together. Such a substancc
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
wc commonly think of as compounds actually show variable composition.
Cuprous sulphide and ferrous oxide arc examples of compounds which
might also be thought of as solutions. No matter how carefully wc made
our definitions of solution, mixture, and compound, wc must expect to
find certain substanccs not to be uniquely classified as one of these. There
is no reason to cxpcct nature to be cooperative and producc only substanccs
which are easily classified, and sincc 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 Russian 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, sincc this is the ease
Ex. 6. Give the English equivalents for the following:
отличаться от, свойства растворов, вещества, которые можно найти
в природе, точно определить,
гомогенное вещество, переменный со*
став, исследовать на молекулярном уровне, четко классифицировать,
в зависимости от эксперимента, нет оснований ожидать
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 i s ... example o f ... compounds wc may consider as ...
solution. 4. ... most useful definitions arc often ... shortest. 5. At ...
molccular 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, sincc
180
1.
Why is it difficult to give a definition of a solution? 2. Solutions arc
among the least known substanccs, 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
substanccs to be found in nature? 6. What definitions arc the most useful?
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