48 HEAT 



Review Questions, 11. 



1. What are the advantages of a sunny house? 



2. How does heat come to us from the sun, in 

 curves or in straight lines? What makes you think so? 



3. Why do you cover your head when you look at 

 the image in a pin-hole camera? 



4. When you are reading at night should you have 

 the light shining directly into your eyes? How should 

 you light your books? 



5. Can you really see a sunbeam ?What do you see? 



6. What color of clothes should we wear in sum- 

 mer? Why? 



7. What is expansion and what causes it? 



8. Do all things expand the same amount? 



19. The Thermometer an Application of Expansion. 



It is warm today? How do you judge? If you have 

 been running it may seem warmer to you than to some- 

 one who has been sitting quietly. The best way to learn 

 about the warmth is by means of a thermometer. This 

 is merely a tube with a large end called a bulb, and is 

 much like the bottle and tube which was used in Experi- 

 ment 24, c. In fact, we can use that apparatus in the 

 place of a thermometer, but the change in the height of 

 the water would be too little to measure easily for ordi- 

 nary changes of warmth. We saw, however, that as th? 

 water became warmer it expanded and ran up the tube. 

 When anything is hot we say that it has a high temper- 

 ature, and when it is cold we call the temperature low. 

 Thus we can make this statement: When the temper- 



