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Unit IV gases

I. Language.

Exercise 1. Read and memorize the words:

abundant - рясний, багатий

except - крiм, якщо не

approximately – приблизно, майже

main - головний

negligible - незначний

combustion - горiння, згоряння

odour- запах , аромат

compress - стискувати , здавлювати

crust - cкоринка, кiрка

dust - пил

pale - блiдий prepare - готувати(ся), пiдготувати

remove - видаляти, усувати

taste - смак

respiration - дихання

vapour - пара slightly – злегка

adjacent – сусiднiй, сумiжний

Exercise 2 . Guess the meaning of the following international words

temperature , tendency , crystal , metal , magnet , gas , inert , activity , combine, element , compress , form , ton , condensation .

Exercise 3. Find the synonymic pairs.

to occur, to combine, several, odour , because of, to compress, approximately , due to, some, to unite, to happen, to contract , perfume , almost .

Exercise 4. Form the antonomic pairs.

abundant, to combine, metal, coloured, tasty, to cool, heavy, to in­crease, non-metal, to disintegrate, rare, colourless, light, to heat, to decrease , tasteless .

Exercise 5 . Define the part of speech of the words below paying attention their suffixes .

supporter , colourless , slightly , heavier , activity , tasteless , greatly , mixture , percentage , approximately , respiration , burner , cheapness , dangerous , inflammable , purity , larger .

II. Reading.

Exercise 6. Read and translate text A “Oxygen “

Text a oxygen

Oxygen is the most abundant element on our planet. In nature, it may occur in a free state or it may occur combined with other elements. Because of its chemical properties, it has been called the most important of all elements to man. It is a supporter of combustion and forms oxides with both metals and non-metals.

Oxygen is a colourless, odourless, tasteless gas. It is slightly heavier than air and is slightly soluble in water. If it were com­pressed and cooled, it would form a pale blue liquid which would boil at - 192.98°C and which would be slightly magnetic. Were it cooled further, it would become a pale blue crystalline solid at a temperature of - 218.7 C.

The outstanding chemical property of oxygen is its activity, that is, its tendency to combine with other substances. It will combine with all the elements except the inert gases. An increase in temper­ature would greatly increase the activity of oxygen. Oxygen, silicon, aluminium and hydrogen together constitute approximately 80 per cent of the Earth's crust, sea and atmosphere. Nitrogen is the main gas in the air, but it is not one of the most common elements. Nitrogen forms only a small percentage of the crust and oceans, and the mass of the atmosphere is negligible compared with the total mass of the Earth.

Air is a mixture of gases. Its composition varies and depends to a large extent1 on plants and animals which control the amounts of oxygen and carbon dioxide by photosynthesis and respiration. Air usually also contains water vapour and dust. If the dust is removed, the approximate composition by volume is the following: nitrogen -78%, oxygen - 21%, argon - 0.93%, carbon dioxide - 0.03% plus small quantities of other gases.

Oxygen combines with metals to form oxides. In this way oxygen can be removed from a sample of air and the amount present in the sample can be measured.

Welding and cutting. In these processes oxygen is used in combination with such gases as hydrogen, acetylene and propane. Much heat is produced during the combustion and metals can be melted to allow either welding or cutting. Oxygen can be used to increase the temperature of the burning hydrogen in the oxyhydrogen burner and of propane in oxypropane burner. Provided burners of this type were used, the temperature would increase up to 3,000°C. Demands for propane are increasing; its advantages over hydrogen and acetylene are its cheapness, its being not as dangerous as the highly inflammable hydrogen and acetylene.

Steelmaking. Oxygen is produced by the ton to convert pig-iron into steel. A plant producing several hundred tons of high pu­rity oxygen per day has to be built adjacent to some of the larger steelworks