Fire and Heat 101 



Exercise. Take equal weights, as one hundred grams, each of 

 water, iron, lead, aluminum. Heat these in a vessel of boiling water 

 until they have a temperature of 100 C. Then put each into a vessel 

 containing one hundred grams of water at zero Centigrade. Stir each 

 mixture with a thermometer until it gives a stationary temperature 

 for two or three readings. Assuming that the loss of heat in transfer 

 and the heating of the vessel is negligible, the results will be approxi- 

 mately these : The one hundred grams of water at 100 C. raises an 

 equal mass of water from zero to 50 C., that is, the quantity of heat 

 given up by hot water is approximately equal to the quantity of heat 

 taken up by the cold water. The results for the other substances 

 are quite different. 



The mass of lead, one hundred grams, at the temperature of 100 C., 

 raises one hundred grams of water from 0C. through about 3. 

 The heat given up by the lead in cooling from 100 C. to 3C., or 

 about 97, is just enough to raise the temperature of the water 3. 

 The same weight of aluminum raises the temperature of the water 

 about 17.6 C., or nearly six times as many degrees as the lead. One 

 hundred grams of iron effects a rise of temperature in the water of 

 about 11.3 C., or just about one half as many degrees as effected by 

 the aluminum. This is a point worth noting regarding aluminum 

 cooking utensil's. 



From these facts it is evident that water is five times better 

 as a receiver and deliverer of heat than aluminum, the best 

 of the substances considered, and is many times superior 

 to 'the others. Indeed scientists have proved that water, 

 weight for weight, takes up a larger amount of heat, holds it 

 better, and gives it up more gradually and in far greater amount, 

 than any other of the ordinary substances. Because of these 

 properties water is not only useful as a medium of heat transfer 

 in warming our homes and public buildings, but is also selected 

 as the standard for measurement of heat capacities of all known 

 substances. 



Exercise. Compare the advantages of hot-water heating with 

 those of the hot-air furnace and steam ; as to cleanliness, ease of con- 

 trol, quietness of operation, fire risk, maintenance of uniform tem- 

 perature, and influence upon the humidity of the air of the room or 

 building. 



