116 Our Surroundings 



SUMMARY 



Heat tends to diffuse and thus equalize the temperature of 

 all places and objects with which it comes in contact. 



Heat is transferred by radiation, by convection, and by con- 

 duction. 



In radiation heat passes from its source in straight lines. 



In convection heat moves from place to place by the flow of 

 a liquid or a gas. 



In conduction heat passes from one object to another by con- 

 tact. 



There are five important modern ways of heating buildings : 

 by the fireplace, the stove, the hot air furnace, the steam heater 

 and the hot water heater. 



The fireplace heats by radiation and by some convection. 



The stove heats by radiation, by convection and by conduc- 

 tion. 



The efficiency of heating buildings by hot air depends upon 

 convection currents. 



The efficiency of steam heating depends largely on convection 

 currents, but radiation and conduction also aid. 



In the hot water method of heating, all three ways of heat 

 transference are employed. 



Ventilation includes the introduction of fresh air into a build- 

 ing and the removal of foul air. 



There are two general methods of ventilation, the gravity 

 system and the forced system. 



A fireless cooker is a device into which hot food is placed to 

 cook without the further use of fire. 



A vacuum bottle is a device for keeping hot liquids hot and 

 cold liquids cold. 



FACT AND THOUGHT QUESTIONS 



1. In what ways is heat transferred? 



2. Why do teakettles often have copper bottoms? 



3. What substances transfer heat by convection? 



4. Explain the hot air method of heating buildings. 



5. Explain the steam method of heating buildings. 



6. Describe the structure of the hot water system of heating. 



7. Describe the plenum system of ventilation. 



