Chemical Change and Energy 313 



which you move come entirely from the burning (oxida- 

 tion) of materials in your body; and that is why you 

 have to breathe ; you need to get more and more oxygen 

 into your body all the time to combine with the carbon 

 and hydrogen in the cells of which your body is made. 

 Plants breathe, too. They do not need so much oxygen, 

 since they do not keep warm and do not move around ; 

 but each plant cell needs oxygen to live ; there is burn- 

 ing (oxidation) going on in every living cell. Fishes 

 breathe oxygen through their gills, absorbing the oxygen 

 that is dissolved in the water. They do not take the 

 water apart to get some of the combined oxygen from 

 it; there is always some free oxygen dissolved in any 

 water that is open to the air. It is clear that fires would 

 all go out and everything would die if burning (com- 

 bining with oxygen) stopped. 



The reason things would not decay is that decay 

 usually is a slow kind of oxidation (burning). When 

 it is not this, it is the action of bacteria. But bacteria 

 themselves could not live if they had no oxygen; so 

 they could not make things decay. 



Not only would the dead plants and animals remain 

 in good condition, but the clothes people were wearing 

 when they dropped dead would stay unfaded and bright 

 colored through all the storms and sunshine. And the 

 iron poles and car tracks and window bars would remain 

 unrusted. For bleaching and rusting are slow kinds 

 of oxidation or burning (combining with oxygen). 



Here are two experiments which show that you can- 

 not make things burn unless you have oxygen to com- 

 bine with them : 



