CHAPTER IV 



BURNING OR OXIDATION 



35. Why Things Burn. The heat of our bodies comes 

 from the food we eat ; the heat for cooking and for warming 

 our houses comes from coal. The production of heat through 

 the burning of coal, or oil, or gas, or wood, is called com- 

 bustion. Combustion cannot occur without the presence of 

 a substance called oxygen, which exists rather abundantly 

 in the air ; that is, one fifth of our atmosphere consists of 

 this substance which we call oxygen. We throw open our 

 windows to allow fresh air to enter, and we take walks in 

 order to breathe the pure air into our lungs. What we need 

 for the energy and warmth of our bodies is the oxygen in 

 the air. Whether we burn gas or wood or coal, the heat 

 which is produced comes from the power which these various 

 substances possess to combine with oxygen. We open the 

 draft of a stove that it may " draw well " : that it may secure 

 oxygen for burning. We throw a blanket over burning ma- 

 terial to smother the fire : to keep oxygen away from it. Burn- 

 ing, or oxidation, is combining with oxygen, and the more 

 oxygen you add to a fire, the hotter the fire will burn, and the 

 faster. The effect of oxygen on combustion may be clearly 

 seen by thrusting a smoldering splinter into a jar containing 

 oxygen ; the smoldering splinter will instantly flare and blaze, 

 while if it is removed from the jar, it loses its flame and again 



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