Their Changes and Properties

Matter exists in three states: solid, liquid, and gaseous. Water, for example, exists sometimes as a solid (ice) and sometimes as vapour (the gaseous state), although we are most familiar with its liquid state. Common salt, for example, exists normally as a solid; at a temperature of several hundred degrees, it can be liquefied; and at still higher temperature it is converted into vapour. Carbon, a solid under normal conditions, can be vaporized, but it has never been liquefied.

Changes from one state of matter to another are accompanied by changes in the energy content of the substance. When one gram of ice melts, 78 calories of heat are absorbed. When the same weight of water is changed into steam at the boiling point of water, 539 calories of heat must be absorbed. The transitions¹ in the opposite direction – vapour to liquid and liquid to solid – are accompanied², of course, by liberation of energy. It should be mentioned³ that some substances change from the solid to the vapour state as the temperature falls, without passing⁴ through the intermediate⁵ state. This change is called sublimation.

 

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 [ˌhɒməˈdʒiːnIəs], heterogeneous [ˌhetərəUˈdʒiːnIəs], sample ['sA: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.

 

Примечания к тексту

1. are not those of water – не являются свойствами воды

2. set of properties – ряд свойств

Запомните следующие слова и словосочетания:

admixture, amount, ash, boiling point, brittle, case, clouded, contain, distinguish, enumerate, feldspar, hardness, heavy, homogeneous, heterogeneous, melting point, mica, mixture, odour, property, pure, retain, sample, set, soluble, specific gravity, substance, transparent, varying, volatility

 

Упражнения

 

I. Найдите в тексте придаточные предложения: определительные и обстоятельства времени, цели, условия и следствия.

II. Дайте анализ следующего предложения:

 

Analytical chemistry has for its aim the determination of the constituents of which a substance or a mixture is composed by methods which are qualitative when the identification is to be carried out or quantitative when the quantity or proportion is determined.

 

III. а) Определите типы придаточных предложений, обращая внимание на союзы. б) Переведите предложения на русский язык:

1. Any element when it combines with oxygen forms an oxide. 2. The methods of determination of specific gravity are well known to everybody as they are used on a large scale. 3. That oxygen can be liquefied only under high pressure was proved by experiments. 4. The process oxygen takes part in is known as oxidation. 5. In order to learn the properties of a substance we must have it in its pure form. 6. Oxygen has been known since the 18^th century. 7. Oxygen can be liquefied provided that pressure is sufficiently high. 8. If sugar and water are mixed, crystals of sugar disappear, but those crystals form again as water evaporates. 9. Whether water or other liquid is used as a solvent depends on many factors.

 

IV. Напишите глаголы, от которых образованы данные существительные:

production, mixture, activity, difference, existence, application

 

V. Сгруппируйте антонимы, переведите их на русский язык:

 

similar, heterogeneous, soluble, different, transparent, colorless, pure, heavy, easily, hard, homogeneous, insoluble

 

VI. Заполните пропуски следующими словами и словосочетаниями и переведите предложения на русский язык:

 

one must, foreign, in order to, properties, turns brown, easily, pure

 

1. Substances are distinguished by their …. 2. Sugar is … soluble in water. 3. Sugar … when it is heated. 4. … learn the properties of a substance … have it in its … form. 5. Small admixtures of … substances change the properties of a substance.

 

VII. Выберите правильный вариант перевода:

 

1.	примесь	а)	brittle
2.	углерод	б)	enumerate
3.	образец	в)	distinguish
4.	полевой шпат	г)	transparent
5.	постороннее вещество	д)	specific gravity
6.	неоднородный	е)	property
7.	свойство	ж)	heterogeneous
8.	удельный вес	з)	foreign substance
9.	прозрачный	и)	feldspar
10.	различать	к)	sample
11.	перечислять	л)	carbon
12.	хрупкий	м)	admixture

VIII. Прочитайте следующие числа:

3.725, 13.819, 12/16, 3/125, ¼, ½, 0.115, 0.003, 5², 3³

 

IX. Ответьте на следующие вопросы:

1. What are the properties substances are distinguished by? 2. Is sugar easily soluble in water? 3. What colour is sugar? 4. Is sugar lighter or heavier than water? 5. What taste has sugar? 6. What is its specific gravity? 7. In what form must one have a substance in order to learn its properties? 8. What may change the properties of a substance? 9. What happens if a drop of milk is added to a glass of water? 10. What substances does granite consist of?

 

X. Проделайте парную работу на перевод с русского языка на английский:

 

А	B
Все окружающие нас предметы состоят из веществ. (All objects surrounding us consist of substances.)	All …
They …	Они состоят из одинаковых молекул. (They consist of similar molecules.)
Гранит состоит из нескольких веществ. (Granite consists of several substances.)
Therefore …	Поэтому гранит состоит из разных молекул. (Therefore granite consists of different molecules.)
Химия изучает вещества и их состав. (Chemistry studies substances and their composition.)	Chemistry …
It …	Она также изучает процессы и законы, по которым происходит изменение их состава. (It also studies processes and laws according to which the change of their composition takes place.)

XI. Прочитайте текст 5 В, не пользуясь словарем:

 

TEXT 5 B