18 



A YEAR IX SCIENCE 



The effect of a change of temperature upon gases. 



A change in the volume of gases is not so readily 

 observed as it is in solids or liquids, because gases are 

 invisible. With the same increase or decrease in tern- 



Fig. 10. When heated, the air in the test tube expands and bubbles 

 of air appear in the water at the open end of the tube. 



perature, gases expand or decrease much more than 

 liquids or solids. This fact is taken advantage of in 

 the construction of thermometers which are to be used 

 to register very slight changes in temperature. In 

 such thermometers air is used. 



Automobile and bicycle tires are not filled with so 

 much air on a hot summer day as they are on a cold 

 winter day. Allowance is made for the expansion of 

 the air in the tire. 



All gases expand at the same rate for the same 



