2 ELEMENTS OF GENERAL SCIENCE 



2. Questions for Discussion. 1. Why does smoke go up a chimney? 

 2. What are the reasons for placing furnaces in basements rather than 

 in upper rooms of buildings ? 3. What is the purpose of a chimney on 

 a house? 4. How should the dampers in a stove or furnace be arranged 

 when a fire is being started? 5. Why does a check draft in a range or 

 furnace cause the fire to burn more slowly? 6. After a fire is started in 

 a cookstove, what changes in the dampers should be made if the oven is 

 to be heated? 7. Why is the hot water in a heater drawn off from the 

 top of the heater instead of from the bottom, near the fire ? 8. Why does 

 "a cake of ice in a refrigerator thaw more rapidly at the top than at the 

 bottom? 9. Why does a paper balloon with a lighted candle at the base 

 tend to rise? 10. Why is a room cooled more quickly if a window is 

 opened at the top than at the bottom ? Would the change of air be 

 more rapid if the window were opened at both top and bottom? 11. If 

 a room is heated from a hot-air register in the floor at one side of the 

 room, why does the opposite side of the room feel warm before the 

 center? 12. If we press an inflated rubber ball and then release it, it 

 will resume its original shape. Why ? 13. When an empty bottle is sud- 

 denly submerged in water, air bubbles rise. Explain this fact. 14. Why 

 does a gas ball not bounce well after it has been punctured ? 15. If air 

 is a gas, why does it hold up the weight of an automobile ? 16. Account 

 for the report that follows the firing of a giant firecracker. 17. What 

 makes the air gun pop? 18. How do air brakes work? 19. Why is it 

 easier to cook food in a closed vessel than in an open one? 20. Can 

 you heat water to a temperature of 125 C. (or 257 F.)? If so, how? 

 21. How can the mercurial barometer be used in approximating the 

 heights of mountains? 22. Why do some people have a pain in the 

 head over the eyes and ears or nosebleed when going up a high moun- 

 tain? 23. A pupil in school is said to require about 2000 cubic feet of 

 air space per hour. Measure the schoolroom and determine the total 

 volume of air in the room. 24. How may the proper amount of fresh 

 air be secured in your schoolroom ? 



3. Air as material. Most of the time we are quite uncon- 

 scious of the air and, in fact, usually ign 0re its existence. 

 For example, if there is a glass tumbler on the table before 

 is does not contain either a liquid or a solid, we 

 it is empty. It is not empty, for it is filled with 

 air; but since air is not visible we ordinarily do not recog- 

 nize its presence (figs. 1 and 2). Similarly, we often say, 



