Heat as a Quantity 165 



Temperature of water . . . . . . 10 



after putting in zinc 15' 2 

 Specific heat of glass 0'188 



The water-equivalent of the beaker is 56 x 0'188 

 = 10-5. Let S denote the specific heat of zinc. Then 



Heat supplied by zinc = 300 x S x (100 - 15' 2) cal. 

 Heat received by water and beaker 



= (515 - 56 + 10-5) x (15-2 - 10) cal. 

 Equating these quantities, we have 



300 x 84- 8tf = 469-5 x 5' 2, or 25,440$ = 2441 '4, 

 whence S = 0-096. 



107. EXPERIMENT 54. Weigh a porcelain dish. In 

 it place a few small lumps of ice, dried by wiping with 

 a duster. Quickly weigh the porcelain dish and ice. 

 Heat the dish over a small Bunsen flame, stirring the 

 ice and the water formed, and noting how long it takes 

 to melt the ice completely. Note the temperature 

 from time to time, and when the ice has all become 

 water, continue the heating till the water has reached 

 a temperature of 20. Make a note of the time required 

 to raise the temperature of the water from to 20. 

 Again weigh the dish and its contents. 



Some of the observations made will be 



(a) That it takes about four times as long to 

 change the ice at into water at the same temperature 

 as it does to heat the water formed from to 20. 



(b) That the water formed by the melting of the 

 ice has the same weight as the ice. 



Suppose the weight of the ice to be 58 g. In 

 raising the temperature of the water formed from 



