24 



Our Surroundings 



COLLECTING OXYGEN 



careful to keep the opening 

 of the bottle covered until it 

 is under the surface. Heat the 

 mixture in the flask and a gas, 

 oxygen, will be given off. This 

 gas will gradually fill the bottle, 

 replacing the water. Cover the 

 mouth of the bottle under water 

 and stand it right side up on the 

 table. 



Oxygen also is made by 

 bringing oxone (sodium perox- 

 ide) in contact with water. 

 Place a piece of oxone the size 

 of a hickory nut under water and collect the gas in a bottle. 



Chemical Action of Oxygen. Insert a glowing splinter into 

 the oxygen and observe the result. This result is oxidation by the 

 chemical union of oxygen with carbon, an essential part of the 

 splinter. The chemical union of any substance with oxygen is 

 oxidation. The most important chemical property of oxygen is 

 its power to make matter oxidize, or burn. 



Other Properties of Oxygen. By use of the senses of sight, 

 taste and smell, find other properties of oxygen. These are 

 physical properties. 



Hydrogen. Hydrogen is a gas. Its most important char- 

 acteristic is that it will combine with oxygen to form water. An 

 important physical characteristic is its extreme lightness, because 

 of which it is extensively used in airships to make them lighter 

 than the air. 



Experiments with Hydrogen. * 



Preparation of Hydrogen. Use a flask with a stopper having 

 two holes, through one of which passes the small end of a thistle 

 tube reaching nearly to the bottom of the flask, and through the 

 other of which passes a short bent glass tube. To the outer end 

 of the bent glass tube attach a rubber tube long enough to reach 

 beneath the surface of water in a tray. Place pieces of zinc in the 

 flask and pour through the thistle tube sufficient dilute hydro- 



