Oxygen

OXYGEN

1. Oxygen is a most interesting as well as useful substance. We depend upon it for life as in its absence we suffocate; for heat because wood, coal and gas do not burn without it; and for light when oil, gas, or a candle is used.

2. Nearly 50% of a terrestrial  matter is oxygen. Water contains about 80 % , the human body over 60 % , and common  materials like sandstone, brick, limestone more than 50 %  of this element. One-fifth by volume (nearly one-fourth by weight) of the air is free oxygen.

It is known that oxygen  is a colourless gas, without taste or odour. Compared with hydrogen, the lightest of all gases, however, it is nearly 16 times as heavy. It can  be liquefied by compression, provided  its temperature is first brought down below  - 118 o (its critical temperature). The critical temperature of a gas is the temperature below which it must be cooled before it can be liquefied by any pressure, no matter how great.

3. Oxygen dissolves slightly in water: 3 volumes of oxygen in 100 volumes of water at 200..  This solubility of oxygen in water is, in some ways, its most important physical property. Fish  obtain the oxygen for their blood from  that dissolved in the water. Man (and breathing animals) cannot take oxygen of the air into the system, if it does not first dissolve in the moisture contained in the walls of the air sacs of the lungs, and then pass inward in a dissolved state to the blood.

4. Liquid oxygen has a pale- blue tint. In an  open vessel (that  is, at the pressure of one atmosphere) its boiling point is 182.50. When more strongly cooled, it freezes to a snow-like solid.

5. In chemical work there are only six physical properties usually mentioned for each  gas: colour, odour, taste, density (referred to some common gas such as air, oxygen, or hydrogen as a standard), liquefiability (whether it is easy or difficult; with oxygen it is difficult), defined by the critical temperature, solubility (usually in water only).

6. All the familiar metals (excepting silver, gold, and platinum) combine , when heated, with oxygen to give oxides. Compound  substances, if they are composed of elements which combine with oxygen, are able themselves to interact with oxygen. Usually, they produce a mixture of the same oxides which  each element separately would give. For example: carbon disulphide burns readily, giving carbon dioxide and sulphur  dioxide, just as carbon  and  sulphur, separately.

1. Прочтите текст и выпишите ключевые слова и словосочетания.

Oxygen, we depend upon it for life, oxygen  is a colourless gas, oxygen dissolves slightly in water, important physical property, liquid oxygen, In chemical work, six physical properties, colour, odour, taste, density, liquefiability, solubility, metals combine, to give oxides.

2. Прочтите предложения и укажите, соответствуют ли они содержанию текста:

а)We don’t depend upon oxygen for life. – No.

b) Oxygen is a colourless gas, without taste or smell. – Yes.

c) It can be liquefied by fusion. – No.

d) Fish obtain the oxygen for their blood from that dissolved in the water. – Yes.