If equal amounts of copper and water are heated, it becomes evident that it takes a great deal more heat to raise 1 lb. of water 1° F. than to raise 1 lb. of copper. The unit of heat has already been defined as the amount of heat necessary to raise the temperature of 1 lb. of water 1 F. The quotient obtained by dividing the amount of heat required to raise the temperature of the substance one degree Fahrenheit and that required to raise the temperature of an equal mass of water one degree is called the specific heat of the body. To illustrate: The specific heat of lead is .031 while the specific heat of water is 1. This means that it would require 31 times as much heat to raise 1 lb. of water one degree in temperature as it would to raise the temperature of 1 lb. of lead one degree.

The following table gives the specific heat of the different substances in which the mechanic and engineer are most interested.

Table of Specific Heat

 Water at 39.1° F...... 1. 000 Ice at 32° F.......... 504 Steam at 212° F...... 480 Mercury............. 033 Cast ron...................... .130 Wrought Iron........ 113 Soft Steel............ .110
 Copper........... 0.095 Lead..................... 31 Coal.............. 0.24 Air............... 238 Hydrogen............... 404 Oxygen........... 0.218 Nitrogen.......... 0.244