THIC SUUSTAXCES OF Till-: KARTII. 25 



Explain the (liU'crencL' between eombustible and incombustible matter. 

 Mention some common substances Avliicli are partly combustible. 

 Mention some whieli are entirely combustible. Name some that 

 are entirely incombustible. 



How much o.\yii,"en is there in the earth? What is an oxide? Ex- 

 plain the process of burninj:;- AV hat is heat ? Why does a fire burn 

 better in a draft of air ? AVliy has decayed wood lost a part of its 

 value for fuel ? Why do we seal fruit to preserve it ? How does 

 breathing; keep the body warm? 



What are the peculiarities of hydrogen ? Why is water produced by 

 burning; hydroi2;en ? Where is nitrogen to be found? Why is it 

 so difficult to obtain it for practical purposes ? 



Name some objects that contain carbon. What proportion of the 

 earth is silicon ? Name some forms in which it is found. Name 

 some of the uses of sulphur. Describe phosphorus. Name some 

 useful forms of chlorine. 



Describe potassium. Name some of the salts of potash. ]\Iention 

 some useful forms of sodium Where is calcium found? How 

 may magnesium be distinguished? Name some forms of aluminium. 

 AVhere does iron exist? 



