Find the predicate in the sentences and define its grammar tense and voice

6. 
   Look! The wheels are rotating.
   
7. 
   All the mice are caught.
   
8. 
   The drilling machine performed perfectly last week.
   
9. 
   The books were brought to the library yesterday.
   
10. 
    These lathes will be checked tomorrow.
    

6. 
   She works in the machine shop.
   
7. 
   The building was fire-proof.
   
8. 
   Modern building materials have been used for this house.
   
9. 
   There’s a kid in the room.
   
10. 
    The lecturer held the discussion yesterday.
    

5. 
   This device was first used in South Africa. ( alternative, special, disjunctive)
   
6. 
   There were plenty of students at the conference. ( general, special, disjunctive)
   
7. 
   The path to the Olympic medal has been easy. (general, alternative)
   

5. 
   He uses the unique equipment. (general, special)
   

1. 
   Study the diagram of this mechanical device. Choose its correct function.
   

1. 
   farming
   
2. 
   exploding mines
   
3. 
   travelling on the Moon
   
4. 
   filming in dangerous places
   
5. 
   carrying things
   

2. 
   List some of the components of this device in the table.
   

Item Quantity

5-metre metal or bamboo poles_______________3

_______________________________________

_______________________________________

_______________________________________

3. 
   Now read the description of how the device works to find the answer to these questions.
   

1. 
   What is the device called?
   
2. 
   What does it do?
   
3. 
   Why is it suitable for the developing world?
   
4. 
   Why do the wheels have steel teeth?
   
5. 
   How often does a wheel have to be changed?
   
6. 
   Why does the machine not miss any mine in its path?
   

The device is called a Dervish. It is a mine-detonating vehicle for clearing anti-personnel mines from farmland in developing world countries. It has a very simple design and uses inexpensive parts. The United Nations estimates that 24,000 people die each year because of mines.

The Dervish has three wheels. Each wheel has steel teeth to create more pressure. When the teeth pass over a mine, it explodes. The wheels can explode around 1,500 mines before they have to be changed.

A motorbike engine powers the Dervish. The device rotates. As each wheel passes a certain point in the rotation, it slows down. This makes the machine advance in tight circles, about 30 mm apart. For this reason no mine in its path is missed.

Liquids are characterized by possessing a definite volume but no fixed form; they take the shape of the vessel containing them, except when in minute quantities, as drops, they assume a form more or less spherical. According to the kinetic theory, the molecules of a liquid are packed close together and attract one another; the attraction is not great enough, however, to prevent their motion. There is not much free space between the molecules, because liquids are very incompressible — a great pressure has little effect in decreasing the volume of a liquid.

Solids possess a definite form. According to the kinetic theory the molecules are closely packed, and the attraction between them is great enough to prevent free motion. It is possible in a solid, therefore, to have a definite arrangement of the molecules which remains fixed; this is seen in the fact that many solids assume definite forms which are characteristic. For example, when sodium chloride separates from a solution in water, it appears as cubes. Other substances appear in other geometric forms. The study of the forms of crystals has developed into a science called crystallography, a knowledge of which is of service to the chemist.
I. Get ready to answer the following questions!
1. What is the characteristic property of a gas? 2. What are liquids characterized by? 3. What form do solids possess? 4. Why has a great pressure little effect in decreasing the volume of a liquid? 5. What science deals with the study of the forms of crystals?
II. Form sentences using the following word combinations:
to prevent motion; the volume of a liquid; a relatively small change in volume; to appear as cubes; according to; to be of little value; the development of science


MATTER AND ENERGY
Before considering the modern views in regard to composition of atoms, it is advisable to review briefly the concepts of matter and energy which are fundamental in all branches of science. A strictly accurate definition of matter is difficult to formulate. Our experience and common sense furnish us with a conception of matter. Matter occupies space; it has inertia, it requires force to set it in motion; it is the stuff of which the universe is made. Energy, on the other hand, is nonmaterial; we become conscious of it only when it is associated with matter.
PHYSICAL PROPERTIES OF PETROLEUM
The colour of petroleum varies from light yellow to red, while some very dark grades are opaque. The higher the specific gravity, the darker the oil.

The nature and composition of crude oil usually determines its odour. Unsaturated hydrocarbons, sulphur and certain nitrogen compounds are responsible for disagreeable odours. Crude petroleum from Russia, Ru­mania and California has an aromatic odour. Pennsylvania petroleum has an agreeable gasoline-like odour. Other oils vary in odour depending on the quantity of light hydrocarbons present in the oil, and of the impurities present. The petroleum from South Texas and Mexico has a strong disagreeable odour, due to hydrogen sulphide and other sulphur compounds. Petroleum is lighter than water. The specific gravity is influenced by physical factors and by the chemical composition of the crude oil. It varies from 0.7684 to 0.992.

The viscosity, or the measure of the resistance to flow, is an important factor with lubricating oils. It is usually stated in terms of the time¹ necessary for a definite volume of oil at a definite temperature to flow through a small opening. The actual work is carried out in an instrument known as a viscosimeter, of which there are several standard makes in use at the present time. Crude petroleums are quite different in viscosity. Some are very mobile, while others, like Mexican crude, are quite viscid. The viscosity increases with the density. The viscosities of oils of the same specific gravity, but from different sources, are not always the same. This is due to the difference in chemical composition.
Get ready to answer the following questions:

1. 
   What is the colour of petroleum? 2. What does its colour depend on? 3. What is responsible for the odour of crude oil? 4. What is the specific gravity of petroleum influenced by? 5. What is the viscosity of crude petroleum?
   

Compressors are used to increase the pressure of gases and vapours for many purposes, e. g. conveying, cleaning, refrigeration, etc. They can be classified as reciprocating, rotary, jet and turbo-compressors.

When the two ends of a conductor are connected to two points at different potentials, such as the terminals of a battery, we say that there is an electric current in the conductor. What actually happens?

The conductor has equal numbers of positive and negative charges in its atoms, and we want to know how the charges can be made to produce a current. The atoms in metals are packed so closely that they overlap to some extent, so that it is comparatively easy for the outer electrons to pass from one atom to another if a small force is applied to them. The battery causes a potential difference between the ends of the wire, and thus provides forces that make the negative electrons in the wire move toward the point of higher potential. This electron flow toward the positive electrode is the electric current. Naturally materials differ considerably in the ease with which electrons can be made to migrate from atom to atom.

The current will not flow unless there is an electric circuit. The magnitude of the current depends simply on the rate of flow of electrons along the conductor.

Electricity is completely intermingled with magnetism. We must know these fundamental properties of a magnet well: a magnet attracts pieces of iron, nickel and cobalt; the magnetic property is concentrated more in the poles: if freely hung the magnetic needle sets itself with one pole toward the north; like poles repel each other, unlike poles attract each other; magnetism can be induced; a magnetic line of force is the path along which an independent north pole would tend to move; a magnetic field is a space in which there are magnetic lines; permeability refers to the ease with which lines of force may be established in any material, and reluctance is the resistance which a substance offers to magnetic lines of force, i. e., to magnetic flux.

Many practical applications have resulted from the utilization, of the magnetic effects of electric currents. These effects are employed in motors, in most electric meters (ammeters, voltmeters and galvanometers), in electromagnets, and in practically all electromechanical apparatus.
BRANCHES OF ELECTRICITY
The study of electricity may be divided into three branches: magnetism, electrostatics and electrodynamics. Magnetism is the property of the molecules of iron and some other substances to store energy in a field of force. Electrostatics is the study of electricity at rest. Rubbing glass with silk produces static electricity. Electrodynam­ics is the study of electricity in motion, or dynamic electricity. The electric current which flows through wires is a good example of the latter type of electricity.

This flow of electricity through a conductor is analo­gous to the flow of water through a pipe. A difference of pressure at the two ends of the pipe is necessary in order to maintain a flow of water. A difference of electric pressure is necessary to maintain a flow of electricity in a conductor. Different substances differ in electrical conductivity because of the ease with which their atoms give up electrons. Electrical energy has intensity and quantity. Instruments have been devised which can be used to measure it in amperes and volts.

From the point of tonnage produced and used, iron is the world's most common metal, followed in turn by copper, zinc, lead and aluminum.

Cast iron is a general term applied to iron-carbon al­loys containing more than 1.7 per cent of carbon. Cast iron without the addition of alloying elements is weak in tension and shear, strong in compression and has low resistance to impact. Grey cast iron has the carbon present in the free or graph­ite state and is soft, easily machined, and only moderately brittle. White cast iron has most of the carbon in the combined state and is therefore hard and brittle.

Steel is a ferrous material with carbon content from 0.1% to 1.0%. Semisteel is a name to a metal made by melting 20 to 40% of steel scrap with cast iron in the cupola. Steel castings are more expensive but stronger and tougher.

Wrought iron is quite ductile and can be easily rolled, drawn, forged and welded. It has high resistance to corrosion. The carbon content is generally less than 0.1% and the material must contain not less than 1% slag.

Cast steel normally contains about 0.5% of carbon, and is used to replace cast iron when castings of considerable, strength are required. Forged steel is steel that has been hammered, drawn, pressed or rolled in the process of manufacturing of a particular part.

Among non-ferrous metals copper is the most important. Because of its high electric conductivity about 60 % of all the copper produced is used in electrical work. Three chief groups of copper alloys used in machine design are brasses (copper-zinc alloys), bronzes (copper-tin alloys), and nickel-copper alloys.

Aluminum is one of the lightest metals used for machine construction. It is commonly used alloyed with copper, silicon or magnesium, the world's lightest structural metal.

Intensive chemical research has created a large num­ber of nonmetallic synthetic materials grouped under the general term of plastics, e. g. bakelite, Plexiglas, textile fibres, synthetic rubber and several protective coatings.

Heat-treatment is the process of controlled heating and cooling of metals to change their structural arrangement and to ensure certain desirable properties.

Annealing consists of heating the metal to a temperature slightly above the critical temperature and then cooling slowly to produce an even grain structure, reduce the hardness, and increase the ductility.

Normalizing is a form of annealing in which the material is cooled in the air.

Quenching or rapid cooling from above the critical temperature by immersion in cold water or some other cooling, medium, is a hardening treatment.

Tempering consists of reheating the quenched metal to restore ductility to some extent and reduce the brittleness.
1. Get ready to answer the following questions:
1. What is the most important non-ferrous metal? 2. What is the difference between brass and bronze? 3. What nonmetallic synthetic materials do you know? 4. What is quenching? 5. What is the difference between annealing and normalizing?
II. What are the opposites of:

Low-carbon steel, strong, tough, stiff, ductile, elas­tic, resistant, brittle, hard, rough, heating, ferrous, mild, steel, tight
PLASTICS
Synthetic plastic materials are now being used in almost every type of industry. They are available in practically all colours and for almost all purposes where metal can be used, except where a very high degree of strength is required. They are lighter in weight than any common metals and are sufficiently hard to take the place of metal parts for most purposes.

Plastics are synthetic in the sense that they do not occur naturally. The molecules are composed principally of carbon, hydrogen, nitrogen and oxygen, which are derived from petroleum, coal, salt, air and water. Their properties depend, to some extent, on size of the molecules of which they are composed.

In early stages of manufacture most plastics are mono­mers composed of small single molecules, but under the influence of heat, or of heat and pressure, or of chemical catalysts these small molecules combine to form long-chain molecules which make up solid or semisolid structures. This process is called "polymerization".

The modern plastics industry deals chiefly with materials manufactured from organic compounds.