Chemical Change and Energy 



307 



FIG. 166. The iron really burns in the jar of oxygen. 



heated. If you stop heating the test tube even for a couple 

 of seconds, take the cork out ; if you do not remove the cork, 

 the cooling gas in the test tube will shrink and allow the 

 water from the pan to be forced through the rubber tube 

 into the test tube, breaking it into pieces. 



When enough gas has bubbled up into the bottle to force 

 all the water out, and when bubbles begin to come up out- 

 side the bottle, uncork the test tube and lay it aside where it 

 will not burn anything ; then slide the cardboard under the 

 mouth of the bottle and turn it right side up; leave the 

 cardboard on the bottle. 



Light a piece of charcoal, or let a splinter of wood burn a 

 few minutes and then blow it out so that a glowing coal will 

 be left on the end of it. Lift the cardboard off the bottle 

 and plunge the glowing stick into it for a couple of seconds. 

 Cover the bottle after taking out the stick, and repeat, using 

 a lighted match or a burning piece of wood instead of the 

 glowing stick. If you dip a piece of iron picture wire in 



