8o 



GENERAL SCIENCE 



more active, so when a substance is heated it will expand 

 and occupy more space without its weight being increased. 

 This can be illustrated by taking a flask completely full 

 of water, closing it with a rubber stopper having a glass 

 tube through it, and heating the water. As the water 

 increases in temperature it will expand up the tube, 

 (if it was 4 C. or warmer at the 

 start) . If a substance will expand 

 when heat is added, what will it 

 do when heat is taken from it? 

 Prove your answer by watching 

 the water in the tube as the 

 water in the flask cools. 



The air expands when heat is 

 applied to it. This can be proved 

 by taking an empty flask (but 

 full of air) and closing it with a 

 cork with a glass tube through it. 

 Hold the flask in both hands with 

 the end of the tube under water. 

 The heat of the hands will warm 

 the air in the flask, and as the air 

 expands it will escape from the 

 water in the form of bubbles. More air can be made to 

 escape by applying a Bunsen flame to the flask. Remove 

 the heat and permit the flask to cool. The water will 

 now flow up the tube into the flask, because the air in the 

 flask contracts as it loses heat. A drop of ink can be 

 made to flow up and down the tube by alternately heat- 

 ing and cooling the flask a few degrees. 



A brass ball which will just slip through a brass ring 

 when both are at ordinary room temperature will not 

 pass through the ring when it is heated. If the ring is 



SHOWING How WATER EX- 

 PANDS WHEN IT is HEATED 



