138 GENERAL SCIENCE 



mass of water through a number of degrees as to raise 

 the same mass of mercury the same number of degrees. 

 Water has a greater capacity for heat than mercury. 

 The ratio of the heat capacity of any substance to the heat 

 capacity of water is called its specific heat. For example, 

 the specific heat of iron is about , or in other words a 

 pound of water in cooling from 100 to will give out as 

 much heat as a pound of iron in cooling from 900 to 0. 



Experiment 40. In one beaker put 200 grams of water at 15 

 and in another beaker put 200 grams of water at 35. Now pour 

 the two together and take the temperature. What temperature 

 would you expect ? Substitute 200 grams of lead shot for the water 

 in the second beaker and repeat the experiment. 



Table of Specific Heats 



Water 1.000 Copper 095 



Alcohol 610 Silver 057 



Ice 504 Tin . . .056 



Aluminum 218 Mercury 033 



Iron . . .-. . . . . .113 Lead 32 



Latent Heat. It was noticed that when heat was 

 continuously applied to a mixture of melting ice and water 

 the temperature did not change but remained near 

 until all the ice was melted. What becomes of the heat? 

 Evidently it represents the work which has been done in 

 effecting the change of state from a solid to a liquid. 

 Eighty calories of heat are required to change a gram of 

 ice at to water at the same temperature. Thus water 

 is said to have a latent heat of eighty calories. Since this 

 heat disappears .when ice or other substances melt and 

 reappears when they solidify, it has been called latent or 

 hidden heat. Although the name is not appropriate it is 

 the one which is commonly used. Heat of fusion is a 

 better name. 



