96 A YEAR IN SCIENCE 



3. Can you suggest any reason why practically all 

 the oxygen of the earth is locked up in water and in the 

 compounds which make up the rocks ? 



4. What keeps up the amount of oxygen in the 

 air when it is constantly being used up by burning ? 



5. A flame is a burning gas. Why do not pure 

 charcoal and iron wire burn with a flame in pure 

 oxygen ? 



6. Name three different ways to obtain free oxygen 

 in the laboratory. 



7. What is burning? Oxidation? An oxide? 



8. What is the significance of opening the draught 

 in the furnace? 



9. What oxidations are valuable? What oxidations 

 does man cause to occur for his comfort ? Mention others 

 which man wishes to prevent. 



10. Describe as well as you can the condition of 

 things if the atmosphere were pure oxygen. Judge 

 from your knowledge of the activity of oxygen. 



11. How is the balance of oxygen in the air 

 maintained ? 



