326 HELPS IN LESSON PREPARATION 



meaning of on the average and purification, page 112. 

 30. About how much air will the cells of the lungs hold on 

 the average ? About how much space would the surface of 

 the air cells of the lungs cover if spread out flat? 31. De- 

 fine inspiring or inhaling, expiring or exhaling, respiration. 



32. What exchange of gases should take place every time 

 we breathe? What is meant by the capacity of the lungs? 



33. Why is it that oxygen is not all used up? 34. Tell 

 how you know oxygen is a wonderful supporter of combus- 

 tion. 35. Give three proofs of the fact that carbonic 

 acid gas will not support combustion. 36. What effect has 

 lime-water on pure air? On carbonic acid gas? What 

 proof have we that burning a splinter in a bottle produces 

 carbonic acid gas? That breathing into a bottle also pro- 

 duces carbonic acid gas? 37. Describe the experiment with 

 the mouse and the glass receiver. 38. State the three 

 facts proved by these experiments. 



CHAPTER XIV 



1. Give antonyms of heavy, deepest, simple, essential, 

 page 118. 2. Describe the experiment with a bladder 

 or toy balloon. 3. How can we tell that warm air is 

 lighter than cold air? 4. Name some conditions that 

 cause differences in temperature in the atmosphere. 5. Tell 

 how the fact that warm air rises helps us to get pure air to 

 breathe. 6. How will the temperature in the upper part 

 of an occupied room usually compare with the temperature of 

 the air in the lower part? 7. Why are we usually sure 

 of pure air when out of doors? 8. Define ventilation. 

 State what openings are necessary for the good ventilation 

 of a room. 9. Compare the components of the air breathed 

 out with those of the air breathed in. 10. Tell about the 

 watery vapor that is given out from the lungs and the skin. 

 11. Give the meaning of disagreeable, odorless, fetid, page 



