EXERCISE 39 



We learned that air is a mixture of several odorless, tasteless, colorless gases, of different specific 

 gravities. Instead of forming layers with the heaviest at the bottom and the lightest at the top, gases 

 in contact spread through each other in all directions, or diffuse. 



Problem. How readily can gases spread and mix (diffuse) ? 



What to use. Several volatile substances with distinct odors for example, carbon bisulfid, perfume, 

 chloroform, ether, alcohol, acetic acid. 



What to do. Open a bottle of one of the substances in the middle of the room ; as soon as pupils in the 

 farthest parts of the room detect the odor, make a note of the time. Repeat with each of the other substances. 



Record. Make a table showing the time required for each of the gases to diffuse a given distance. 



Questions. 1. What kind of gases seem to diffuse most quickly? 



2. How does an electric fan affect the diffusion of gases ? 



3. What would be the practical effect if the gases in the air were not evenly diffused ? 



