Примечания к тексту

1. transition – переход

2. accompany – сопровождать

3. it should be mentioned – следует упомянуть

4. without passing – не переходя

5. intermediate – промежуточный

X. Расскажите, что вы знаете о различных формах материи и о их свойствах.

LESSON 5

Грамматика. Обстоятельственные придаточные предложения причины, места, условия, цели и уступительные.

Предтекстовые упражнения

I. Определите типы придаточных предложений. Переведите следующие предложения на русский язык:

A.

1. Since aluminium is light and strong, it is widely used in industry. 2. One must be careful with mercury as it is poisonous. 3. Because carbon monoxide is odourless, its presence is not easily detected.

B.

1. I found the book where I had left it. 2. He put the test-tube where the teacher told him. 3. Wherever she lived, she always found friends.

C.

1. If a piece of tin is warmed, it melts. 2. Water freezes at 0⁰ unless it contains salt. 3. Oxygen can be liquefied provided that pressure is sufficiently high. 4. You will finish your experiment in time provided you work hard.

D.

1. We heat ice so as to melt it. 2. In order to know what happens when a metal rusts we must study the properties of metals before and after rusting occurs. 3. I shall give you the article immediately so that you may be able to translate it in time. 4. You must put down the words lest you should forget them. 5. The vessel was closed in order that the liquid might not evaporate.

E.

1. He finished the experiment in time though (although) it was very difficult for him. 2. However busy he may be, he will prepare his report.

II. Переведите предложения, обращая внимание на значение следующих слов и словосочетаний:

to turn + black (прилагательное) – чернеть, становиться черным

Acids are substances that turn blue litmus red.

to learn – учить

All the students of our University learn chemistry.

to learn – узнавать

We learned the news from the newspapers and the radio.

III. Прочитайте следующие многосложные слова:

property, enumerate, century, particle, energy, possible, chemical, general, quantity, physical, molecule, molecular, similar, oxygen, visible

IV. Запомните произношение следующих слов:

admixture [ədˈmɪkstʃə], transparent [trænsˈpærənt], granite [ˈɡrænɪt], homogeneous [ˌhɒməˈdʒiːnəs], heterogeneous [ˌhetərəˈdʒiːnəs], sample ['s:mpl]

TEXT 5 A

Substances

Substances are distinguished by their properties – colour, smell, taste, specific gravity, greater or less hardness, melting and boiling points, volatility, etc. For example, in describing the properties of sugar, one can state that sugar is a hard, brittle substance, white in colour, sweet to the taste, without odour, easily soluble in water, heavier than water and it turns brown when it is heated, etc.

In order to learn the properties of a substance one must have it in its pure form. Even small admixtures of foreign substances may change the properties of a substance. For example, pure water is both colourless and transparent, but if a drop of milk is added to a glass of water, the water becomes clouded; if a drop of ink is added, the water becomes coloured. All the enumerated properties are not those of water¹ but they are properties of admixtures.

In some cases, one may see at once that a substance is heterogeneous, that is, a mixture of different substances.

Granite, cement, petroleum are examples of non-homogeneous materials; they consist of mixtures of substances. Thus, granite is a mixture of varying quantities of silica, feldspar, and mica, each of which possesses its own set of properties². Coal is not a substance too because different samples contain different relative amounts of ash, water, carbon, and other components.

Every material, therefore, consists of a single (pure) substance, or it is a mixture of two or more substances, each of which retains in the mixture its own characteristic properties.