CLASSES OF SUBSTANCES 191 



QUESTIONS 



1. What class of elements are commonly called negative? 

 What are positive elements ? Name some elements in each class. 

 What is a radical ? Name two radicals. 



2. Define an acid. What properties do acids generally pos- 

 sess? Name any acids that you can. Name any substances that 

 you think may contain an acid. 



3. What is a base ? Name four common bases. For what are 

 these sometimes used ? What is an alkali ? 



4. Name several metals. Are they elements, compounds, or 

 mixtures ? How are the metals generally obtained ? 



5. Under what conditions is a salt formed? Name any salts 

 that you can. Are salts very numerous ? Are they important ? 



6. In what ways are salts obtained ? Name uses of salts. 



7. What is an oxide? Name any oxides that you know of. 



8. What sort of substances compose minerals? Are minerals 

 compounds or mixtures ? 



9. What is an ore ? Does the metal in an ore occur in a free 

 state or combined with other elements? Name metals that are 

 obtained from ores. 



10. What is an alloy? Name some common alloys. 



11. Name the elements that compose hydrocarbons. Name 

 any common hydrocarbons. 



12. What elements combine to form carbohydrates? Name 

 any such compounds, telling where they commonly occur. 



13. What is a solution? Is it a confound or a mixture? 

 Name some common solvents. What is a soluble substance ? 



14. When is a solution saturated ? What condition in the sol- 

 vent may assist the dissolving ? Of what use are proteids ? 



15. What sort of substance is a tincture ? What is an essence ? 

 What is an amalgam ? 



16. Name the class of substances to which each of the follow- 

 ing belongs : iron ; copper sulphate ; sugar ; mercury ; kerosene ; 

 common salt ; gelatin ; household ammonia ; starch ; iron rust ; 

 lead; brass; gasoline. 



