№ 4. Magnets and magnetic fields
Words to be remembered:
piece – кусочек
iron ore – железная руда
to suspend – подвешивать
position – положение
to point – указывать
approximately – приблизительно
behavior – поведение
loadstone – магнетит, магнитный железняк
artificial – искусственный
magnetic field – магнитное поле
steel rod – стальной стержень
to hit – ударить
partially – частично
to repel – отталкивать
compass needle – стрелка компаса
pole – полюс
The ancient Chinese knew that pieces of certain natural iron ores, when suspended by a string, take a definite position with one end pointing approximately north and the other approximate south. It is clear from the behavior of the magnetic compass of loadstone and other magnets both natural and artificial.
We can use the magnetic field of the earth to magnetize steel rods if we hold them in the direction of the magnetic field of the earth and hitting them repeatedly with a hammer. The violent impacts shake the tiny particles of the rod and orient them, at least partially, in the direction of the field.
If we bring two magnetized steel rods close together, we find the ends pointed the same way during the magnetization process, to repel each other and if one of the rods is turned around, the ends of the rode attract one another.
This behavior shows that a long piece of magnetized material - or a compass needle - shows its magnetic properties most strongly in the region near its end, known as the poles of the magnet. Poles that point toward this same direction repel each other.
Questions on the text:
1) What did the ancient Chinese know? 2) What can we use the magnetic field of the earth for? 3) How can we magnetize steel rods? 4) What happens if we bring two magnetized steel rods together? 5) Where does a long piece of magnetized material show its magnetic properties most strongly?
№5 . SOME FACTS ABOUT ATOMS
Words to be remembered:
to exist – существовать
arrangement in molecules – расположение в молекуле
to determine – определять, устанавливать
investigation – исследование
essentially – по сути
be referred to – (зд.) называться
to believe – считать, полагать
to revolve – вращаться
central core – центральное ядро
positively charged – положительно заряженный
to form – формировать, образовывать
compound – соединение
nucleus – атомное ядро
number – количество
a number of – ряд
An atom may be spoken of as the smallest particle of any substance. If atoms cannot be seen it does not necessarily mean that they do not exist. It indicates that any particle, if present, must be extremely small. There are methods by means of which the sizes of atoms and their arrangement in molecules can be determined. One of these methods uses X-ray diffraction.
In the course of many investigations, chemists came to a conclusion that the atoms of different elements are all made essentially of three simple types of units, which were referred to as protons, neutrons, and electrons. We now believe that an atom is composed of a cloud of electrons that revolve about a central core of protons or of protons plus neutrons. Repeated experiments show that every atom has the same number of electrons as well as protons. The positively charged protons form the nucleus of the atom. The neutrons are also found in the nucleus of the atom.
It was also found that many elements and compounds are composed of small numbers of atoms which are held together in a regular arrangement. These groups of atoms are referred to as molecules.
It is known that ninety-two elements occur in nature, and a number of others have been made by man in the laboratory. Every element is a special combination of protons, neutrons, and electrons. Each element is identified by the number of protons in its nucleus and is designated by a name and a symbol.
Element Number 1 is a combination of one proton and one electron. Long before its atomic structure was known this element was referred to as hydrogen, or "water-former", because water forms when hydrogen burns in air. Its symbol is H.
Questions on the text:
1) What is an atom? 2) Can we see atoms? 3) How can we determine the sizes of atoms? 4) What are atoms made of? 5) What forms the nucleus of the atom? 6) What are molecules? 7) How many elements occur in nature? 8) How is each element identified? 9) What is element number 1?
№ 6. LIQUIDS
Words to be remembered:
liquid – жидкость; жидкий
solid – твердое тело; твердый
state – состояние
volume – объем
definite shape – определенная форма
vessel – сосуд
in contrast to – в отличие от
to fill – заполнять, наполнять
to compress – сжимать
close – близкий, тесный
to increase – увеличивать, повышать
to occur – происходить, случаться
depend upon – зависеть от
transition temperature – переходная температура
to place – помещать
layer – слой
dense – плотный
soluble – растворимый
to disturb – беспокоить, нарушать
it is to be taken into consideration – нужно учитывать, нужно помнить
to flow (flew, flown) - течь, фильтроваться
friction – трение
to generate – (зд.) возникать
to vary – меняться, изменяться
vapour – пар
evaporation – испарение
recondensation – последующая конденсация
The liquid state occupies an intermediate position between the gaseous and solid states, liquid having a definite volume but no definite shape.
Like a gas, a liquid can take the shape of any vessel in which it is put, but in contrast to a gas, a definite quantity of liquid is required for filling the vessel. A liquid can not be compressed so much as a gas because its molecules are already close together, large pressure producing small changes in volume.
Increasing the temperature increases the kinetic energy of all molecules.
The change of a liquid into a gaseous or solid states being dependent upon the kinetic energy of the molecules, which in turn is dependent upon the temperature, there are definite temperature characteristics for most liquids at which these changes occur. They are known as transition temperatures.
If we place one liquid layer carefully on top of a layer of a more dense liquid in which it is soluble, and set the vessel where it won't be disturbed, we shall see that two liquids begin gradually mixing. It is also to be taken into consideration that all liquids do not flow with the same ease, water, alcohol, gasoline flowing easily, while heavy oil glycerine flowing very slowly.
When a liquid flows, layers of molecules begin rubbing over each other, friction is generated by this rubbing of layers of particles. The greater the friction, the slower is the flow.
The molecules of a liquid are much closer together than they are in a gas, because of the greater relative strength of attraction. The density of liquids is much greater. Naturally as the volume of a liquid begins varying with temperature its density will also start varying with temperature.
The escape of the molecules from a liquid into its vapour is called evaporation. After a sufficient number of molecules have collected in the space above the liquid, their haphazard wanderings bring them back to the surface as fast as other molecules escape. Thereafter, there is a balance between evaporation and recondensation.
Questions on the text:
1) What is a liquid state? 2) What is the difference between a liquid and a gas?
3) What does the change of a liquid into a gaseous or solid state depend on? 4) What are transition temperatures? 5) What liquids flow easily? 6) What liquid flows very slowly? 7) Why do some liquids flow very easily and some flow very slowly? 8) How is friction generated? 9) What is evaporation?
№ 7. SOLID STATE
Words to be remembered:
paper clip – скрепка для бумаги
to bend (bent, bent) – сгибать, гнуть
to break (broke, broken) – ломаться
ductile – упругий
glass rod – стеклянный стержень
brittle – хрупкий
to conduct electricity – проводить электричество
electrical transmission lines – линии электропередач
insulator – изолятор
opaque – непрозрачный
reason – причина
to behave – вести себя
behavior – поведение
to reveal – открывать, обнаруживать
to assume – предполагать
to turn out – оказываться, выясняться
If you take a paper clip and bend it, it would stay bent, it wouldn't spring back and it wouldn't break. The metal of which the clip is made is ductile. Some other materials are not ductile at all. If you tried to bend a glass rod, (unless you are holding it in a flame), it would simply break. It is brittle. In this respect as in many others, glass behaves quite differently from a metal. The difference must lie either in the particular atoms of which metals and glass are made up or in the way they are put together, probably both. There are of course many other differences between metals and glass.
Metals, for example, conduct electricity and therefore are used for electrical transmission lines, glass hardly conducts electricity at all and can serve as an insulator. Glass being transparent, it can be used in windows whereas a sheet of metal even more than a millionth of an inch thick is quite opaque. It is of course interesting to understand the reasons of these differences in behavior.
We should remember that metals conduct electricity well and most materials do not.
Only the discovery of an electron helped the scientists to understand some of this fact well. With the discovery of an electron it was assumed that in metals some or all of the atoms had lost an electron and that in insulators such as glass they had not. It turned out that electrons in a metal move freely, whereas the electrons in insulators do not. Why did this happen in metals? This very question had to await the discovery of quantum mechanics. The next question was «How are the electrons arranged?»
As far as this question is concerned we can say that solids can be divided into two clasps: crystalline and amorphous. In the crystalline group, which is the largest and includes the metals and most minerals, the atoms are arranged in a regular way.
Questions on the text:
1) Why wouldn’t a paper clip spring back or break if you bend it? 2) Why wouldn’t a glass rod bend? 3) Why does glass behave differently from a metal? 4) Do we use glass for electrical transmission lines? Why? 5) Can we use a sheet of metal in windows? Why? 6) What did the discovery of an electron help the scientists understand? 7) Why do some material conduct electricity and some don’t?
№ 8 . CHEMISTRY
Words to be remembered:
to deal with – иметь дело с чем-либо
property – свойство
composition – состав
to take place – происходить, случаться
goods – товары
manufacture – производство
homogeneous – гомогенный, однородный
heterogeneous – гетерогенный, разнородный
to consist of – состоять из
to decompose (into) – разлагать (на)
alloy – сплав
common – обычный, распространенный
in order to – для того, чтобы
standard of living – уровень жизни
phenomenon, phenomena (pl)– явление, явления (мн.ч.)
descriptive – дескриптивный, описательный
in part – частично
separation – сепарация, разделение
at present – в настоящее время
to maintain – поддерживать
definition – определение
Chemistry is the science which deals with materials, their properties and the transformations they undergo. So chemistry is the study of the composition and properties of matter, their changes, the conditions under which such changes take place, and the energy changes which accompany them.
Chemistry is concerned with the nature of fire and the structure of water, it deals with colours, catalysis and crystal structure, with physical properties and chemical reactivity.
Chemistry is one of the fundamental sciences. It plays an important part in the development of biochemistry, physics, geology and many other goes of science. Chemistry's origin goes back to ancient times, with the manufacture of bronze, iron, ceramica, glass.
Everyone now understands the importance of chemistry. The future of chemistry is practically unlimited. Rapid development of chemical industry will make it possible to create many new goods, machines, plastics, polymers, it will help to understand many new phenomena.
It is to be remembered that:
1. Chemistry is the study of substances, their structure, properties, and their
reactions.
2. Matter exists as solids, liquids, or gases.