XI. Прочтите вопросы перед чтением текста и ответьте на них
What is your attitude to Chemistry? Chemistry is often referred to as the central science – do you agree with this statement? What do you mean by “Pharmaceutical chemistry”? Why is development of this science extremely important? Do you know who described the first periodic table of the elements that ordered the elements by increasing atomic weight and according to trends in their properties? (It was not Dmitri Mendeleev. The actual inventor of the periodic table is someone rarely mentioned in chemistry history books).
XII. Прочтите текст и скажите, какие химические элементы упоминаются в тексте:
Text A. Pharmaceutical chemistry
Chemical Elements
At present there are 110 known chemical elements. (The discovery of element 110, reported in 1987 by Soviet scientist, remains unconfirmed, however, and is still considered extremely tentative.) Elements can combine with one another to form a wide variety of more complex substances called compounds. The number of possible compounds is almost infinite; perhaps a million are known, and more are being discovered every day. When two or more elements combine to form a compound, they lose their separate identities, and the product has characteristics quite different from those of the constituent elements. The gaseous elements hydrogen and oxygen for example, with quite different properties, can combine to form the compound water, which has altogether different properties from either oxygen or hydrogen. Water clearly is not an element because it consists of and actually can be decomposed chemically into the two substances - hydrogen and oxygen; these two substances, however, are elements because they cannot be decomposed into simpler substances by any known chemical process. Most samples of naturally occurring matter are physical mixtures of compounds. Seawater, for example, is a mixture of water and a large number of other compounds, the most common of which is sodium chloride, or table salt. Mixtures differ from compounds in that they can be separated into their component parts by processes; for example, the simple process of evaporation separates water from the other compounds in seawater. Mendeleyev's periodic table of 1869 contained 17 columns, with two nearly complete periods (sequences) of elements, from potassium to bromine and rubidium to iodine, preceded by two partial periods of seven elements each (lithium to fluorine and sodium to chlorine), and followed by three incomplete periods. In an 1871 paper Mendeleyev presented a revision of the 17th group, the principal improvement being the correct repositioning of 17 elements. He, as well as Lothar Meyer, also proposed a table with eight columns obtained by splitting each of the long periods into a period of seven, an eighth group containing the three central elements (such as iron, cobalt, nickel; Mendeleyev also included copper, instead of placing it in Group I), and a second period of seven. The first and second periods of seven were later distinguished by use of the letters "a" and "b" attached to the group symbols, which were the Roman numerals.
|
|
|
TASKS
Read the text B and comment on the figures.
Text B. Water
About 3 quarters of the earth surface are covered with liquid water. Water can be in liquid, solid and vapour condition. As it can change its condition it constantly moves and influences everything on the Earth.
In vapour form, water is also an important constituent of the earth’s atmosphere. It occurs in animals and vegetable tissues. It constitutes some 70 % of the human body and over 90 % of some vegetables. So water is very important to all living things. In the living body water carries foodstuffs from 1 part of the body to another.
Man gets one half of his water in the food he eats, especially in fruit and vegetables.
More than 70 % of the body is composed of water. Daily we lose some water. The human body gives off about 5 pints of water every 24 hours through the lungs, sweat glands and kidneys. We must replace it. If 10% of the body is lost without replacements, there will be serious signs of illness. Water losses greater than 15% are usually fatal. A person can go without water about 7-10 days.
Potable water is water which is fit to drink. Since water dissolves a part of nearly everything with which it comes in contact, absolutely pure water does not occur in nature. The water for drinking and domestic purposes is generally supplied by rivers, lakes, wells, and springs. Such waters commonly contain salts of calcium, iron, magnesium, potassium, and sodium, organic matters from falling leaves and twigs; and traces of carbon dioxide, oxygen, nitrogen, ammonia, and other gases from the atmosphere.
|
|
|
There is also a variety of suspended matter in natural water such as fine particles of clay, sand, microscopic organisms including bacteria, and fragments of vegetation. Waters having appreciable amounts of dissolved salts are always more acceptable for drinking than those free from solids. But good drinking water must be free from toxic salts, disease producing organisms, and from harmful organic and sewage contamination.
Words:
vapour-пар; constituent- составная часть, элемент; to occur- встречаться, иметь место; foodstuff- продукты питания; to compose- составлять; to dissolve- растворять; sweat – пот; replacement- замещение; pint- пинта, ≈ 0,5 л.; potable water- питьевая вода; contamination- загрязнение
II. Finish the sentences using the following words:
for drinking, free from toxic salts, acceptable, average, salts, calcium, microscopic organisms, fine particles, natural waters, pure, magnesium, potassium, bicarbonate, clay, sand, sodium
1. We have mineral waters in which the total mineral content is significantly above the … . 2. Alkaline waters contain unusual quantities of … . 3. The water for drinking and domestic purposes commonly contains … . 4. There is also a variety of suspended matter in … . 5. Waters having appreciate amounts of dissolved salts are more … . 6. Good drinking water must be … .
III. Answer the questions:
1. Is water distributed in nature?
2. In what states of aggregation does water occur in nature?
3. How many quarters of the earth’s surface are covered with liquid water?
4. Where does water occur?
5. What is the composition of water?
6. What kinds of water do you know?
7. What water is fit to drink?
8. Does water play a vital part in the nutrition of animals and plants?
9. Where is water employed by man?
10. Does absolutely pure water occur in nature?
LESSON 6
Грамматика:пассивный залог; слова – заменители
Дата добавления: 2018-02-28; просмотров: 1581; Мы поможем в написании вашей работы! |
Мы поможем в написании ваших работ!