IX. HOUSEHOLD CHEMISTRY 

 A REVIEW OF SOME CHEMICAL CHANGES 



1. So common are chemical changes in everyday life, 

 and so important are these to our well-being and comfort, 

 that it will be profitable to recall some already studied in 

 connection with others more or less familiar in home 

 affairs. 



What in general is the nature of the chemical change 

 that occurs in stoves and furnaces in warming our houses? 

 What explanation is there for the heat produced in our 

 bodies ? What are the products of the oxidation (a) of car- 

 bon; (6) of hydrogen? 



2. How is it that low temperatures, lack of moisture, use 

 of preservatives, and the common processes of canning, 

 hinder or prevent the decay of organic foodstuffs? Name 

 some preservatives of foods that are (a) wholesome; (6) 

 prohibited because they may be harmful. 



3. What is the significance of the term fermentation? 

 What is the general purpose of the changes in the processes 

 of digestion? Into what stage of chemical change in foods 

 does fermentation lead if unchecked? What in some cases 

 is the nature of the ailment called indigestion? Why in 

 the fermentation of cider to make vinegar, and in the sour- 

 ing of milk, does the increase of acid cease after a time? 

 Explain the destructive action on the teeth of decaying food 



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