10 SMITH'S INTERMEDIATE CHEMISTRY 



Iron (100) -f Oxygen (43) - Ferric oxide (143). 

 Lead (100) + Oxygen (7.72) -> Oxide of 'ead (107.72). 



The following numbers, which represent the same proportions 

 by weight, are the ones commonly used by chemists : 



Iron (223.36) + Oxygen (96) - Ferric oxide (319.36). 

 Lead (414.4) + Oxygen (32) -> Oxide of lead (446.4). 



Summary. Thus far, we have learned that chemistry deals 

 with substances and their specific properties, and with the changes 

 which substances undergo. We have discussed and defined a 

 number of important words expressing fundamental chemical 

 ideas. Finally, we have touched upon the weights of the ma- 

 terials used in chemical change, a subject of great importance 

 which will be more fully developed in a later chapter. 



Exercises. 1. Describe the following, by mentioning some of 

 their specific properties-: (a) water, (b) wool, (c) cotton (pp. 1-3). 



2. If any of the following are mixtures, mention the facts which 

 show them to contain more than one substance (p. 3) : (a) muddy 

 water, (b) an egg, (c) milk. 



3. State and illustrate the first two laws of chemistry (pp. 6, 7). 



4. Make definitions of " pure " and " impure " as applied to a 

 sample of a substance (p. 6). 



5. Give a list of specific properties mentioned in this chapter. 



6. In recognizing a specimen to be quartz, does the chemist 

 consider (a) the weight, (b) the temperature, (c) the length of the 

 specimen (p. 7 )? If not, why not? 



7. Take one by one the words or phrases printed in black type 

 and the titles of the sections in this chapter, and endeavor to 

 recollect what you have read about each. In each case try, 

 (a) to recall the meaning and to state it in your own words; (6) to 

 recall the facts associated with, and the reasoning which lead up to 

 the point in question; (c) to recall examples illustrating the con- 

 ception and to apply the conception in detail to each example. 



