PAPERS ON CHEMISTRY AND PHYSICS 239 



along which his high school training taught him to tread. 

 Although the ^Yeather Bureau records will show that the 

 entire week from Januaiy 20 to 28 showed zero weather, 

 still it evidently never occurred to him that it was possi- 

 ble for him experimentally to answer his own query. His 

 attitude of mind was not exceptionally remarkable. A 

 fair length of life and constant observation leads me to 

 believe that many other high school graduates are as de- 

 pendent upon authority in all scientific matters as he ap- 

 pears to be. 



Naturally, I read this letter to an advanced class in 

 physics, and the pedagogy of physics teaching was dis- 

 cussed. In that class no one appeared in doubt as to 

 whether the hot water or the cold water would freeze the 

 sooner. One of my physics students carried the question 

 into an advanced class in pedagog^^ That class was di- 

 vided in judgment as to whether the hot water or the cold 

 water would freeze first. Not being a science class, judg- 

 ments were based necessarily upon knowledge of physical 

 laws and upon reasoning formulated upon the remem- 

 bered laws and princiiiles of physics. I was told that 

 the discussion was animated and the conclusion was about 

 fifty-fifty in favor of the hot and the cold water. 



One member of that pedagogy class, a man of middle 

 age, a high-school graduate and a man of many years ex- 

 perience as a teacher, was much interested in the question. 

 Like the writer of the letter, he wanted a statement from 

 some authority. He could not find it in textbooks and so 

 he appealed to me. I questioned him as to his own con- 

 clusion. He readily gave it together with his reasons for 

 drawing that conclusion. He said the hot water would 

 freeze first for two reasons: First, '^Physics teaches 

 that the molecules of hot water are in rather rapid mo- 

 tion, while the molecules of cold water are not. There- 

 fore, the molecules of the boiling water would come rapid- 

 ly and frequently in contact with the sides of the contain- 

 ing vessel or to the surface. Therefore, the molecules of 

 the hot water would lose their heat much faster than the 

 molecules of cold water." Second, ''Hot water evapo- 

 rates much faster than cold water and every gram of 

 v^ater which evaporates carries off 5.36 calories of heat. 



