CONDUCTION OF HEAT 67 



poke as long as we wish and our hands will not be burned. 

 That is because wood is a poor conductor. Most metals 

 are good conductors of heat, although some metals do 

 not conduct heat as well as others. Water is a poor con- 

 ductor of heat. 



Experiment 34. Good and Poor Conductors of Heat. 



Apparatus: Alcohol or gas lamp, pieces of copper 

 and iron wires No. 12, 6"long, test tube. 



a. Hold the end of the copper wire in one hand and 

 the end of the iron wire in the other hand, and put the 

 free ends into the flame of a burner. Which one be- 

 came warm first? Which is the better conductor? Hold 

 the poor conductor in the flame and notice that it takes 

 a long time to become hot at the hand. 



b. Fill the test tube nearly full of water and place 

 as shown in the flame of a burner, so that the top of the 

 water is heated. Do not let the flame touch the glass 

 where there is no water, as 



it will break. When the 

 water boils at the top how 

 it the bottom? Is water a 

 food or a poor conductor oi 

 heat? If vou wanted tn 

 heat water where would you 

 heat it, at the bottom or 

 top? How does the ocean 

 become heated, at the top or 

 the bottom? 



