THE NATURE AND NEEDS OF LIVING MATTER 19 



Conclusions. 1. How could you determine the presence of 

 oxygen in some substances ? 



2. How account for any differences in the oxidation of the 

 splinter in air and in oxygen ? 



Note. The burning of the splinter, accompanied by flame, 

 is an example of rapid oxidation or combustion. 



Method b (Home Exercise). Place an iron nail in a small 

 bottle filled with water. Cork and seal the bottle. Place 

 another iron nail in a shallow vessel containing a little .^vater. 

 Examine the nails from time to time. Which nail is most 

 exposed to oxygen ? 



Observation. Which nail has changed in appearance the 

 most ? In what way ? 



Note. The rusting of iron 

 means its union with oxygen to 

 form iron oxide, etc. Since no 

 flame is present, this is an ex- 

 ample of slow oxidation. 



Conclusions. 1. What is the 

 process of rusting ? 



2. If heat is one result of 

 oxidation, where does the heat 

 of your body come from? Is 



this rapid or slow oxidation? FIG. 3. -Diagram of rapid oxidatiou 

 TT . _ ,_ T1 or combustion in a stove. 



Heat is a torm ot energy. Why 



oxidize coal in a locomotive furnace ? 



3. What is the relation between rapid oxidation and the 

 release of energy ? Would slow oxidation be satisfactory in 

 a locomotive ? Is rapid oxidation necessary in our bodies ? 

 Explain. 



c. Hydrogen (H) (Optional) 



Note. This element is present in all foods, and composes two thirds of 

 water by volume. 



Apparatus. Iron nails or tacks, weak sulphuric acid, wide-mouth 

 bottle, small glass tube drawn to a point and placed in a 1-holed rubber 

 stopper that fits the bottle. 



Oxygen in the air 



V 



