44 Our Surroundings 



FACT AND THOUGHT QUESTIONS 



1. Where is air found? How can you tell there is air all about you? 



2. Of what does air consist? In what proportions? 



3. Of what special value to life is the oxygen in the air? Could one 

 breathe pure oxygen? 



4. What is the value of the nitrogen in the air? 



5. Why is carbon dioxide dangerous in large quantities? How can you 

 determine if it is present in dangerous amounts? Name some situation 

 in which it would be wise to employ this test. 



6. Mention an important use of carbon dioxide. 



7. What would happen if you poured a glassful of carbon dioxide gas 

 into a glassful of air? Why? 



8. When is air good, and when bad? 



9. Illustrate and explain the proper method of breathing. 



10. Mention several general properties of air. 



11. Describe simple experiments to illustrate two properties of air. 



12. What is a barometer ? 



13. Complete, orally, these statements : 



(a) Breathing is more difficult as we ascend to great heights, because. 



(b) At sea level, the column of mercury in a barometer stands at 

 about inches. 



14. Name several toys which depend on properties of air. 



15. Name several machines or appliances which make use of air pressure. 



16. If you had a tank of carbon dioxide gas and a tank of oxygen, which 

 should you draw on to put out a fire ? Why ? 



PROJECTS 



1. Make a popgun out of the bark of a tree. Use it, and explain the 

 action of the air in it. 



2. Make a siphon. Use it, and explain its action. 



3. Take apart a hand air pump. Show how it works to compress air. 

 Make labeled drawings to illustrate its workings. 



OUTDOOR OBSERVATION 



1. Fly a kite and observe the effect of air upon it under different con- 

 ditions. 



2. In the course of a walk, list your observations and impressions of air 

 as given you by your senses. 



REFERENCES 



The Wonder Book of the Atmosphere Houston 



Fresh Air and How to Use It 



National Association for Study of Tuberculosis 



