OXYGEN AND OXIDATION 49 



filled with oxygen gas it can be removed from the shelf 

 by slipping a glass plate under its mouth while still in 

 the water; it can then be placed on the desk in an up- 

 right position. Leave the bottle covered to prevent any 

 possible mixture of the oxygen with the air. This will 

 permit the filling of as many bottles as desired. To pre- 

 vent the breaking of the test tube, remove the delivery 

 tube from the water before you take the flame away from 

 the test tube. Why? 



Properties of Oxygen Gas. Put into a bottle of oxygen 

 gas a splinter of wood with a glowing spark on the end, 

 and note the result, (i) Oxygen supports combustion 

 or burning. (2) It will stay in the upright uncovered 

 bottle, and will flow out if the bottle is inverted; hence 

 it is heavier than air. (3) It is tasteless, colorless, and 

 odorless. Try it and see. 



35. Oxidation. Oxidation is a process in which the 

 atoms of oxygen unite with the atoms of other substances 

 to form new compounds. Oxidation liberates a great 

 amount of heat. The heat energy necessary to draw 

 trains, drive automobiles, keep our houses and bodies 

 warm, all comes from the burning of carbon or carbon 

 compounds. When oxidation occurs so rapidly that a 

 flame is produced, it is commonly called burning, as coal 

 or gas burns in a stove or furnace. 



We saw in 34 that oxygen supports combustion or 

 burning. The great quantity of oxygen in the air is one 

 source of its supply. The earth itself is composed of about 

 45 per cent of oxygen. With all of the great fires that we 

 have in factories, in machines, and in buildings to produce 

 heat energy, the per cent of oxygen and carbon dioxide 

 of the out-door air does not change much. The reason for 

 this is that plants use carbon dioxide and liberate oxygen 



