202 COMMON SUBSTANCES 



8. In what form does iron occur in the earth ? What is the 

 symbol for iron ? How is iron obtained from its ores ? What is 

 pig iron ? How is steel made ? 



9. Name salts of Na that are important ; also salts of K. 

 Explain the action of these elements upon water. 



10. Name important salts of Ca that occur in the earth, and give 

 common names for each. What is lime ? For what is lime used ? 



11. Describe the element Hg. Name some of its uses. Name 

 two of its common salts, stating the use of each. 



12. In what form does each of these metals occur : Cu, Ag, 

 Au, Pb, Sn, Zn ? Name uses of each. 



13. Describe the element Al. In what forms does it occur? 

 What familiar compounds does it form? 



14. In what form does Si largely occur? What is its most 

 common compound? What is a silicate? 



SECTION II 

 COMPOUNDS 



235. Water. Water is a compound of hydrogen and 

 oxygen; its molecule contains two atoms of H and one 

 atom of O, its symbol therefore being H 2 O. Water is a 

 most important compound, occurring not only in rivers, 

 lakes, and oceans, but in the earth and the atmosphere 

 (as vapor). Water is evaporated from the ocean, etc., 

 and taken into the air as vapor; here it is condensed 

 and falls to earth as rain. Some of this water sinks 

 into the earth, flows along on hard rock as underground 

 streams, and later comes to the surface again through 

 springs or wells. Mineral waters are found in streams 

 that dissolve some of the rock through which they flow. 

 Rivers carry much material from the surface of the land 

 to the ocean ; this has been going on for so long that 



