Some Applications of Heat 117 



8. Do all metals when heated expand to the same degree? 



9. Describe the vacuum system of ventilation. 



10. Compare advantages and disadvantages of (a) stove and furnace 

 heating; (b) hot air and steam heating. 



11. Why does a fire "draw" better if the height of the chimney is in- 

 creased? 



12. Why is smoke from a newly kindled fire sometimes driven back 

 into the room instead of going up the chimney? 



13. How does a chimney protect health? 



14. Why may snow melt from a house roof while the outside tempera- 

 ture is below freezing? 



15. How is ventilation related to heat by convection? 



16. Why is it better to make stoves of iron than of stone? 



17. Describe the vacuum bottle. 



18. How does the vacuum bottle prevent the escape of heat? 



19. Why are furnaces and furnace pipes often covered with asbestos or 

 other slow-conducting material? 



PROJECTS 



1. Construct a labeled diagram of a steam heating system. 



2. Make a fireless cooker. 



3. Study and describe the heating system of your home. Show how it 

 distributes heat, and how it supplies fresh air and moisture. Experi- 

 ment with the drafts and determine their effects. 



OUTDOOR OBSERVATION 



Take a walk and record observations on the effects of low temperature 



in streams and in stone crevices. 

 Note effects of extreme heat on cement walks, on asphalt and on moist 



soil. 



REFERENCES 



Household Physics Butler 



Fireless Cooker Farmers' Bulletin 771, U. S. Dept. of Agriculture 



