PART II. WATER AND ITS USES 



CHAPTER X 

 ICE, WATER, AND STEAM 



130. Questions for Discussion. 1. Why is it that your breath can 

 be seen in cold air and not in warm? 2. How hot is boiling water? 

 Can you heat it past the boiling point? 3. Why do campers on high 

 mountains experience difficulty in cooking food ? By what methods 

 can foods be cooked in such places? 4. Can water possibly be made 

 to boil at less than 100 C.? Is there any advantage in this? 5. Will 

 water boil at the same temperature if something is dissolved in it? 



6. In cooking potatoes by boiling, can the time of cooking be mate- 

 rially shortened by using a hotter fire after the boiling has started? 



7. What common animals are cooled by perspiration? Name several 

 that are not cooled by this means. 8. May there be evaporation from 

 a snow bank during cold weather? 9. Why is hot weather less oppres- 

 sive in dry regions than in moist ones? 10. Why is it undesirable to 

 sit in a draft of air immediately after vigorous exercise? 11. Why are 

 alcohol baths used in cases of fever? 12. How does a thermos bottle 

 keep hot things hot, and cold things cold? 13. What advantages from 

 cold-storage plants have resulted to city populations? to country 

 populations? 14. Why are your feet colder when you are standing in 

 melting snow than when you are standing in freezing snow? 



131. When water freezes. What happens when water 

 freezes? Perhaps most of us have observed nothing more 

 than that when water gets cold it changes into a solid, and 

 when it becomes a solid it may break the containing vessel. 

 The temperature at which water freezes is, under ordinary 

 circumstances, always the same. In making the centigrade 

 thermometer the freezing point of water is taken as the start- 

 ing point in making the scale, and that point is called zero. 

 What is the freezing point on the Fahrenheit thermometer? 



113 



