Symbol O. Atomic Weight 15,9.

Priestly, in England, discovered oxygen on the first of August 1774, when he heated oxide of mercury by means of the sun’s rays concentrated by a burning glass. It was afterwards discovered independently by Scheele, in Sweden, in 1775.

Properties of Oxygen. Oxygen is at an ordinary temperature a colourless, odourless and tasteless gas, heavier than air and slightly soluble in water. 100 volumes of water at 0⁰ can dissolve 4 volumes of oxygen under the normal pressure of 760 mm. It is converted into a liquid at a low temperature and a high pressure. It boils at ­­–– 181⁰C.

Occurrence. Of all the elements, which occur on our planet, oxygen either free or combined is the most widely diffused and is found in the largest quantity. Oxygen occurs in the free state in the atmosphere, of which it forms one fifth by volume. In combination with hydrogen it forms 8/9 of the total weight of water on the earth’s surface. It occurs very plentifully in a state of combination in all rocks and is an essential constituent in all animal and vegetable structures.

Preparation. It is prepared by heating certain of its compounds, some of which are mercuric oxide, potassium chlorate and manganese dioxide; it may be obtained by the decomposition of water by electrolysis.      

 

XII. Translate the following word-combinations into Russian:

occur on the planet, free or combined, widely diffused, largest quantity, in a free state, in the atmosphere, combinations with the hydrogen, an essential constituent, heavier than air, under the normal pressure, at a low temperature.

 

XIII. Find in the text the English equivalents to these word-combinations.

увеличительное стекло, горная порода, при обычной температуре, тяжелее, чем воздух, при низкой температуре, превращаться в, широко распространенный, в свободном состоянии или в соединении, общий вес,  электролизом.

XIV. Translate the following sentences into Russian:

1.The experiments show that oxygen does not act upon sulphur and carbon when brought in contact with them at an ordinary temperature.

2. Oxygen is an essential constituent of air and water.

3. Oxygen is made by heating a mixture of potassium chlorate and manganese dioxide.

4.It is absorbed from the atmosphere by animals and plants during respiration.

5. Oxygen is at ordinary temperature a colourless, odourless and tasteless gas.

 

XIV. Translate the following word-combinations into English:

самая высокая температура, самый большой объем, самая низкая температура, тяжелее, чем воздух, легче, чем вода, самое большое количество, самый широкий.

 

XV. Tick the sentences that are true and change the false ones.

1. Firstly discovered oxygen on the first of August 1972.

2. Oxygen is at ordinary temperature a colourless, odourless gas.

3. Oxygen is easier than air.

4. It is converted into a liquid at a high temperature and low pressure.

5. It boils at 171 C.

6. Oxygen either free or combined is the most widely diffused and is found in the largest quantity.

 

XVI. Make up a plan of retelling.

XVII. Retell the text.

 

Lesson V

Nitrogen

Rules of reading: Letters Ii, Yy

Word formation: suffix -ly

Grammar: construction neither...nor, either...or...

Text: Nitrogen

                                                   

Assignments to do:

Remember:

a) Ii,Yy are pronounced as followings:

    

                  1st type of reading            2nd type of reading

                           [ai]                                       [i]

                 life, my                                              in, introduce

                 tie, type                                        it, infinitive

                                                                                   

b) adverbs are formed with the help of the suffix - ly:

     usual - usually

     bad - badly