18 THE NATURE AND NEEDS OF LIVING MATTER 



3. Does nitrogen support burning (combustion) ? 

 Note. The air is composed mostly of oxygen and nitrogen, 

 plus small amounts of water vapor, carbon dioxide, argon, etc. 



b. Oxygen (0) and Oxidation 



Apparatus. Test tubes, potassium chlorate, black oxide of 

 manganese, alcohol lamp or Bunsen burner, bent glass tube, 

 1-holed rubber stopper to fit test tube, wide-mouth bottle, dish 



of water. 



General Method. 

 Heat half a teaspoon- 

 ful of the chlorate of 

 potash with slightly 

 less than the same 

 amount of black oxide 

 of manganese. The 

 resulting gas may be 

 collected over water 

 as indicated in Figure 

 2, or the tests may be 

 made in the test tubes 

 in which the oxygen 

 is made. 



Method a. Light a 

 splinter of wood, blow 

 out the flame, but see that the end is still glowing. Plunge 

 the glowing end in a test tube in which oxygen is being set 

 free. 



Observations. 1. What happens to the glowing coal ? 

 2. What difference between the burning of the splinter in 

 air and in oxygen ? 



Note. When oxygen combines with any substance, heat is 

 always released. The process is named oxidation. The sub- 

 stance with which the oxygen unites is said to be oxidized. 

 The element or substance oxidized in this case is carbon. 



FIG. 2. Making and collecting oxygen, t, test 

 tube; e, delivery tube; n, chemicals; 0, oxy- 

 gen collecting. 



