THE MEASUREMENT OF HEAT 107 



while being raised 1C. is called the SPECIFIC HEAT of that 

 substance. 



So it is evident that the heat an object possesses depends 

 upon three factors: (1) Its weight; (2) its temperature; (3) 

 the material or substance of which it is made. 



121. Units of Heat Quantity. 



DEFINITIONS. 1. One unit is the amount of heat necessary 

 to raise 1 gram of water lC. It is called the LESSER CALORIE 

 and this is usually abbreviated, thus: 1 cal. 



2. A second heat unit is the amount of heat necessary to 

 raise 1000 grams, or 1 Kg., of water 1C. It is called the 

 GREATER CALORIE and is usually abbreviated, thus: I Cal. This 

 is the unit generally used by European engineers in calculating 

 all large quantities of heat, such as are required in heating 

 buildings. 



3. A third unit is the amount of heat required to raise the 

 temperature of 1 Ib. of water 1F. This is called the BRITISH 

 THERMAL UNIT. In writing it is usually abbreviated, thus: 

 1 B.t.u. This is the unit commonly used by British and 

 American engineers. 



PROBLEMS 



1. How many lesser calories (cal.) of heat are absorbed when 20 

 grams of water are raised 5C.? 



2. 500 cal. of heat will raise 25 grams of water from 20C. to what 

 temperature? 



3. How many greater calories (Cal.) are absorbed when 50 Kg. 

 of water are raised from 15C. to 25C.? 



4. 800 Kg. of water are to be heated from 15C. to 100C. How 

 many Cal. of heat will be required? 



5. If 40 Ib. of water are raised from 18F. to 80F.; how many 

 B.t.us. are consumed? 



6. How many B.t.us. of heat are required to raise 50 Ib. of water 

 from the freezing point to the boiling point? 



7. How many B.t.us. are given off when 80 Ib. of water are cooled 

 from 180F. to the freezing point? 



122. How Heat is Measured. Calorimetry. Heat is 

 measured by means of an instrument called a CALORIMETER. 



