46 NATURAL RESOURCES OF HOME ENVIRONMENT 



There is dust in practically all the air we 

 breathe. 



Impurities in the air. 

 If you allow a beam of 

 sunlight to pass through 

 a small crack into a 

 darkened room, you will 

 see thousands of tiny 

 specks floating in the air. 

 These little particles are 

 perhaps soot, dust, or 

 other bodies. In some 

 cities, like Pittsburgh, 



the smoke is always a constant factor, although it does 



not seem to harm people very much, but where factories 



are numerous, we sometimes get poisonous fumes or gases 



as part of the air we 



breathe. 



Combustion. We 



have seen from the 



experiments we have 



performed that when 



the gas oxygen is 



present, wood or a 



candle may be 



burned. Heat and 



light always accom- 

 pany this burning. 



Combustion or burn- 

 ing in pure oxygen 



is much more intense 



than it is in air. 



Iron and other metals 



can be burned in 



What kinds of oxidation are shown here ? 



