232 ELEMENTARY GENERAL SCIENCE CH. xv 



QUESTIONS ON CHAPTER XV. 



1. Describe experiments which prove that air is composed of at 

 least two gases. 



2. How would you show by experiments that only one part of the 

 air is concerned in (a) burning, (b) rusting ? 



3. Describe experiments indicating that rusting and burning are 

 essentially similar operations. 



4. Describe briefly the sequence of experiments which .indicate 

 the existence of oxygen in air, and give a mode of preparation of 

 this gas. 



5. How is oxygen most conveniently prepared ? Give an account 

 of its characteristic properties. 



6. What are oxides, and how may they be obtained ? 



7. How can nitrogen be obtained from the air, and what are its 

 chief properties ? 



8. By what experiments may the presence of (a) aqueous vapour, 

 (b) carbon dioxide, in the air be indicated. 



9. Describe experiments which prove that during rusting and 

 burning an increase of weight occurs. 



10. How would you find the quantity of oxygen and nitrogen 

 present in a given volume of air ? ~ 



11. By the combustion of different substances various oxides may 

 be produced. Point out how by the action of water these oxides 

 may be divided into two classes, and give examples. 



12. Describe (a) a direct, (b) an indirect method of finding the 

 weight of a litre of oxygen. 



13. What is argon ? How has it been obtained ? 



14. To what are flames due ; what is a reducing flame, and what 

 is an oxidising flame ? 



15. On what does the luminosity of a flame depend ? 



16. The gas obtained by burning a mixture of coal gas and oxygen 

 is not very luminous. How may it be utilised as a source of intense 

 light ? 



17. What is meant by incandescence? What is the cause of the 

 incandescence jn (a) an electric lamp, (b) an incandescent gas light ? 



18. What is the difference between an ordinary flame and that of 

 a Bunsen burner ? 



19. Oxygen and nitrogen are the two chief ingredients in common 

 air. State reasons for the usual belief that they are not combined 

 together chemically. 



