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This element is most widely distributed in nature; 49.85 per cent of the solid crust of the earth, 88.89 per cent of water and 20.8 per cent of air is oxygen. In nature it exists in limestone, sand, marble, clay, quartz, iron, and many other substances. It is prepared by heating certain of oxygen containing compounds, some of which are mercuric oxide, potassium chlorate and manganese dioxide; it may be obtained by the decomposition of water by electrolysis.
Oxygen is at ordinary temperature a colourless, odourless and tasteless gas, heavier than air and slightly soluble in water. 100 volumes of water, at 0º can dissolve 4 volumes of oxygen under the normal pressure of 760 mm. At a low temperature and a high pressure it is converted into a liquid which boils at -181ºC.
1. Answer the following questions:
1. Is oxygen widely distributed in nature?
2. In what state does oxygen exist in air?
3. Where does oxygen exist in a combined state?
4. In what way is oxygen
5. What are the substances oxygen may be prepared from?
6. What are the properties of oxygen?
7. Is oxygen lighter than air?
8. Is oxygen readily soluble in water?
9. How many volumes of water can dissolve 4 volumes of oxygen at 0º?
10. Under what conditions is oxygen converted into a liquid?
11. At what temperature does liquid oxygen boil?
2. Pick antonyms:
1) to exist in a free state
4) to combine
5) low pressure
3. Put the verbs in brackets into the desired shape of the passive voice:
1) Oxygen ....... widely ....... (Distribute) in nature.
2) In a combined state it ....... (Include) in limestone, sand, marble, clay and
3) Oxygen ...... .. (prepare) by heating certain of its compounds.
4) Decomposition of water by electrolysis ...... .. (use) for obtaining oxygen.
5) Oxygen ... (contain) in air in a free state.
6) 4 volumes of oxygen can ...... (dissolve) in water at 0 and the normal pressure.
7) Oxygen ...... (convert) into a liquid at a low temperature and at a high
4. Move the syllables in a word, to get new words:
Tunare, soldi, denoxy, tonelimes, deoxi, rwate, lesscolour, vesoldis, liidqu,
5. Put questions to the selected words:
1) Oxygen is most widely distributed in nature.
2) It contains in limestone, sand, marble, clay, quartz and many other
3) Oxygen is at ordinary temperature a colourless, odourless and tasteless gas.
4) In air it exists in a free state.
5) It is prepared by heating certain of oxygen containing compounds.
6) Oxygen is slightly soluble in water