140 ELEMENTARY SCIENCE 



molecular motion, but what we commonly cell heat is 

 simply that degree of molecular motion which we happen 

 at the time to feel, but there are vast amounts of heat all 

 about us which we never feel at all. Heat is a great 

 phenomenon of nature of which our senses alone enable 

 us to perceive only a tiny fraction. 



QUESTIONS 



1. What is cold? 



2. Explain conduction of heat. 



3. Explain how ice-cream is frozen. 



4. Why does the water of the ocean not freeze at the same tem- 



perature as the water of the Great Lakes freezes? 



5. Why is Chicago warmer in winter than cities farther away from 



the lake? 



