84 THE SUN'S GIFT OF HEAT 



perature of equal quantities of different substances also 

 varies. If a pound of water and a pound of olive oil are 

 placed side by side in similar dishes on a stove, it will be 

 found that the olive oil increases in temperature about 

 twice as fast as the water, i.e. it takes about twice as much 

 heat to raise water as it does to raise the same weight of 

 olive oil one degree. In fact, it takes more heat to raise 

 a given weight of water one degree than it does to raise 

 the same weight of almost any other known substance. 



In Experiment 29, the resulting temperature from the 

 water mixture was much higher than from the water and 

 shot mixture. The shot has much less capacity for heat. 

 The quantity of heat required to raise the temperature of a 

 certain mass of a substance one degree compared to the 

 quantity of heat required to raise the same mass of water 

 one degree is called the specific heat of that substance. 

 The specific heat of olive oil is .47, of shot .03. That is, 

 it takes .47 as much heat to raise a given mass of olive oil 

 and .03 as much heat to raise a given mass of shot one 

 degree as it does to raise a corresponding mass of water 

 one degree. In order to compare different quantities of heat, 

 physicists have taken as the unit of measure the quantity 

 of heat required to raise the temperature of one gram of 

 water through one degree C. This unit is called a calorie. 



The Effect of Heat upon the Condition of a Substance. 



Experiment 30. Having filled two tin cups or beakers of the same 

 size to an equal height, one with water and the other with a mix- 

 ture of water and ice, place them side by side on a stove or over 

 Bunsen burners so adjusted as to give approximately the same 

 amount of heat. (Figure 39.) Stir each with a chemical thermom- 

 eter, and make a note of its temperature. 



After heating a few minutes, stir again and note the tempera- 

 ture. Have there been like changes in the temperatures of the 



