ELEMENTS, COMPOUNDS, AND MIXTURES 257 



gate a room with sulphur, it is only necessary to close 

 the room and burn sulphur in it. Sulphur is also used 

 as a bleaching agent for those fabrics and materials 

 which would be injured by chlorine. The fumes from 

 sulphur are poisonous and should not be breathed in large 

 quantities. 



Carbon. Of all the non-metallic elements carbon is 

 the most abundant. There are only three non-metallic 

 elements which are solids at ordinary temperatures 

 carbon, phosphorus, and sulphur. 



Carbon appears in many common forms in the impure 

 state, as coal, soot, or lampblack, charcoal and graphite, 

 or the black lead of our lead pencils. It is found in 

 considerable quantities in all vegetable and animal sub- 

 stances. When such substances are burned, the black 

 carbon is exposed to view. When wood is charred, when 

 toast is burned, or when meat is scorched, the black 

 which appears is carbon. If the combustion is complete, 

 the carbon disappears and only the mineral ash is left. 



Except in the case of the diamond, carbon is a black 

 solid. The diamond is so different in appearance and 

 properties from the other forms of carbon graphite, 

 charcoal, soot, and coke that it is hard to believe that it 

 is the same element. However, if these substances are 

 burned in pure oxygen, they all form the same product, 

 carbon dioxide. This proves conclusively that they are 

 the same element. 



QUESTIONS 



1. Give four examples of physical change. 

 Give four examples of chemical change. 



2. What is oxidation ? 



3. What is an element? A compound? A mixture? 



4. How do you know iron to be an element? 



