24 THE PRINCU^LES OF AGIUCL'LTURE. 



QUESTIONS. 



How many different elementary sii1)?tanees are there in tlie cartli? 

 Xame those which are most common. Name as many others as 

 vou can thinlv of. What is meant by the symbol of a substance ? 

 Name the symbols of the most comuion substances. 



What is an atom ? Have atoms ever been seen? llovf do we know 

 that they exist? How are atoms represented? Give an idea 

 of the size of an atom. Can an atom be divided? Can it be 

 destroyed ? 



What is a molecule? W^hat causes atoms to form molecules? How 

 is a molecule represented ? How are the atoms of a molecule 

 arranged ? 



Upon what does the nature of matter depend? ]\Iust all substances 

 composed of carbon, hydi-ogen, and oxygen be alike? Can the 

 molecules of a body be broken or dividt'd? How can this l)e done? 

 W^hat effect does this have uj)i)n a body ? AVhat would be the 

 effect of making a different arrangement of the atoms in the mole- 

 cules of a substance ? 



W^iat is chemical action ? Give an example of chemical action, and 

 explain it. 



What are acids? Bases? Salts? Name some of each. 



Give a chemical equation showing how bases are fo.-med. 



What is cohesion ? What is adhesion ? Why does your hand become 

 wet when dipped in water? AVhy are the feet kept dry by greas- 

 ing the boots? How is water purified by leaching through char- 

 coal ? Whv are not two pieces of wood touching each other held 

 together l)y cohesion ? 



How many porous substances are there? How do we know that iron 

 is jiorous? Why can salt lie nddcd to a glass full of water without 

 causing it to run over? Why may two gases appear to occui»y the 

 same space at the same time ? 



Explain the difference beween solids, liquids, and gases? Why is a 

 substance melted bv heating it? How is it that heat expands and 

 cold contracts? Why does water expiind in freezing? 



W^liat is the difference between organic and inorganic matter? Is 

 hay organic or inorganic? A polato? AYater? Milk? Sand? 

 Ordinarv soil ? 



