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Examine the effects of atmospheric air pressure on both the filling of a large bottle with water and on the emptying of water from the bottle.
 

PERFORMING THE EXPERIMENT

Be careful not to spill any water outside of the tub while performing this activity.  Keep the bottle inside the tub during the entire filling process and over the tub during the entire emptying process.

1. Partially fill the glass bottle with water by holding the mouth of the bottle under the water level in the plastic tub.  What problems do you observe as you fill the bottle?  Why do they happen?  How could the problems that you observed be avoided?    (NOTE:  Keep these problems in mind as you later empty the bottle!)
   
   
2. Fill the bottle the rest of the way by dipping water from the tub using the tennis ball container.
   
   
3. Your task is now to empty the completely filled bottle into the tub as fast as you can.  Your adult partner will time you as you tip the bottle over and pour the water back into the tub.  (If the bottle is too heavy for you to handle, switch places with your adult partner.  Tell your adult partner how to hold the bottle, and let your adult partner empty the bottle while you be the timer.)
   
   
4. On the signal of "GO," pour the bottle as fast as possible into the tub. 
   
   
5. If you get an idea as to how to do it faster during the first trial, test your idea by trying the experiment a second time.
   
   
6. On the data sheet, write your first and last name neatly and the times you required for emptying the bottle. 
   
    

QUESTIONS TO THINK ABOUT

1. What is the problem in terms of emptying the bottle rapidly?  Does it only have to do with getting the water out?

2. When water empties from your bathtub, does it gurgle the way at least some of the water did as it was leaving your bottle?  Why not?

3. What causes the swirling motion of the water at the bathtub drain?  Does this help the tub empty faster? 
 

EXPLANATION

Air gurgles out of the bottle as you try to fill it by holding the mouth under the surface of the water.  In the same manner air gurgles into the bottle when you try to empty it.  The gurgling air should be a clue that the problem is getting air out of the bottle rather than getting the water in when you are trying to fill the bottle.  Likewise, the problem is getting air into the bottle rather than getting the water out when you are trying to empty the bottle.  (Gravity takes care of getting the water out!)  Therefore, when emptying the bottle, you must devise a method of getting air into the bottle while gravity pulls the water out.  A method may be demonstrated at the end of the program.
 

EQUIPMENT NEEDED

Plastic tub half-filled with water; 5-pint or similarly sized glass bottle (a plastic soda bottle collapses); smaller plastic container such as a tennis ball container for easy filling of the large bottle; cloth towel.
  

Kids Involved Doing Science is at http://www.kids.union.edu.

Modified 02/22/2001 by C. & P. Scaife