LIVING IN AN OCEAN OP AIR 



2. Pour 50 cc. (about 2 oz.) of limewater into the jar. Close 

 and shake. There is only one common gas, carbon dioxide, that 



causes limewater to become milky. 1 If we find a change from 

 clear to a milky liquid, what does it prove? 



What substances does this demonstration suggest are produced 

 when oxygen of the air combines with the candle? 



It may seem strange to you to find that water comes 

 from the burning of a candle. But if you know that 

 oxygen in the air is a gas that supports 

 the burning of the candle, then it is 

 easily understood. The candle con- 

 tains hydrogen and carbon. Both of 

 these elements will burn. The hydro- 

 gen unites with oxygen and forms 

 I water (H 2 0). The carbon unites with 

 oxygen to form carbon dioxide (CC^). 

 These two compounds also result from 

 the burning of other substances con- 

 Where will water appear taining hydrogen and carbon, such as 



in the jar after the candle & J 



bums for a short time? gasoline, oil, coal, and wood. They 

 HOW do we know it comes are therefore, always present in the 



from the candle ? , . ' , . 



smoke coming from chimneys. 



The Air Is Useful in Many Ways. The air of the at- 

 mosphere was just as useful to Columbus as was the 

 water of the ocean, for while the ocean buoyed up his 



1 To show that it is carbon dioxide that turns limewater milky, generate 

 the gas by adding hydrochloric acid to marble chips in a test tube and 

 conduct the gas through a delivery tube, making it bubble through lime- 

 water in another test tube. 



