EXPERIMENTS IN CHEMISTRY AND PHYSICS 17 



caused by the friction of the match head against the striking surface is 

 enough to cause the phosphorus to ignite; this in turn ignites the sulphur 

 and finally the wood of the match, composed largely of the element carbon, 

 is lighted and oxidized. If we could take out the different chemical ele- 

 ments of which the match is formed and oxidize them separately we should 

 find that the amount of heat needed to start the oxidation of the 

 substances would vary greatl3\ The element phosphorus, for ex- 

 ample, is kept under water in a glass jar because of the extreme 

 readiness with which it unites with oxygen. 



Experiment. — Oxidation may take place with very little heat 

 present, although heat is always a result of oxidation. 



Place an iron nail in a bottle of water, and cork and seal the bottle. 

 Place another nail in a saucer in which 

 is kept a little water. Note the for- 

 mation of rust on the nail in the 

 saucer and the absence of rust on the 

 nail in the bottle. Rust is iron oxide 

 and is formed by the union of iron 

 and oxygen. This kind of oxidation 

 is said to be o, slow oxidation. Slow 

 oxidations are constantly taking place 

 in nature and result in the process of 

 decay and breaking down of complex 

 materials into simpler materials. 





Oxyqen in the air 

 ^ 



3 



Diagram of combustion or rapid oxida- 

 tion in a stove. 



Heat given off as result of Oxidaticn. — One of the most im- 

 portant effects of oxidation lies in the fact that, when anything is 

 oxidized, heat is produced. This heat maybe of the greatest use. 

 Coal, when oxidized, gives off heat; this heat boils the water in 

 the tubes of a boiler; steam is generated, wheels of an engine 

 turn, and work is performed. The energy released by the burning 

 of coal may be transformed into any kind of work power. Energy 

 is the ability to perform work. 



Carbon. — Another chemical element of much importance to 

 us is carbon. This element makes up an important part of all 

 things that now have or at any time had life. Such matter we 

 call organic. Carbon is found making up part of the bodies of 

 plants and animals, of coal, and in a nearly pure state in the 

 diamond. The presence of carbon can often be detected by the 

 fact that the substance containing it turns black upon being 

 heated in a flame. 



Experiment. — Heat separately on a tin plate some leaves, sticks of wood, 

 gravel, sand, and rich black earth. Place them over a hot flame for some 

 minutes Which of the above materials contains carbon? 



If some substance that contains carbon, as a piece of wood, is burned in a 

 jar with a tight-fitting cover, the flame will be seen to go out after a short 



hunter's BIOL. — 2 



