Heat as a Quantity 



163 



0-237 



0-142 



0-033 



0-188 



0-5 



0-906 



0-397 



0-550 



3-41 



0-214 



1 calorie to be supplied to raise its temperature by 

 1 C., the specific heat of water is 1. 1 g. of mercury 

 only requires 0"033 heat-units to raise its temperature 

 by the same amount, hence the specific heat of mercury 

 is 0'033. The specific heats of some common substances 

 are given in the table below : 



Copper . .. 0'094 Air 



Zinc .. . .. 0-094 Copper oxide 



Iron .. . .. 0'114 Mercury 



Lead 0'031 Glass 



Tin .. . .. 0-055 Ice 



Aluminium . .. 0'219 Blood 



Alcohol . .. 0-615 Stearic acid (solid) . 



Olive oil . .. 0-471 (liquid) . 



Turpentine . . . 42 Hydrogen 



Petroleum . . . 0*511 Sodium chloride 



Paraffin wax . .. 0'694 



Note. In all cases where the scale of temperature is not 

 definitely mentioned in the following pages, the Centigrade scale is 

 to be understood. 



105. The method of working simple examples in 

 which the specific heats of the substances used must 

 be considered is shown below. 



Example 1. Suppose an iron cylinder weighing 

 100 g. to be used in Experiment 53. What will be 

 the temperature of the water after the iron has been, 

 placed in it ? 



Let this temperature be denoted by n. 



In cooling from 60 to n, the iron will lose 

 100 x (60 n) x 0*114 calories. To raise the tempera- 

 ture of the water from, say 15 C., to n C., will require 

 400 x (n 15) calories to be supplied. Supposing no 

 heat to be lost in heating the beaker and its surround- 

 ings, these two quantities of heat must be equal, i.e. 

 100 x (60 - n) x 0-114 = 100 x (n - 15). 



Solving this as a simple equation in n, we have 

 11T4 = 2184, or n = 19'6 C. 



11-2 



