Pamela S. Moy - Morgan Park High School

Surface Tension

Pamela S. Moy                  Morgan Park High School
                               1744 West Pryor 
                               CHICAGO IL 60643
                               (773) 535-2550 

Objective(s):

 This activity is written for third to eighth grades or as an introduction to 
  the topic.  Depending on how you choose to supplement the information this 
  miniteach may be used for higher or lower levels.
 Students will become familiar with surface tension.
 Students will determine if soap and heat will affect surface tension.
 
Materials Needed:

 For all to use:  One hot plate and a large beaker

 For each group you intend to have:
 Four small clear plastic cups
 Water
 Two boxes of gem clips (paper clips)
 Dishwashing liquid (just a few drops)
 Paper towels
 Black pen for labeling
  
Strategy:

 1.  Label four cups with A, B, C, and D.
 2.  Place a beaker of water on the hot plate and heat it until it reaches a  
     boil (be very careful it will be hot).
 3.  While waiting for the water to boil, fill Cup A to the brim with tap 
     water.  Do the same for Cup B.  Be sure the water in each cup is exactly  
     to the rim of the cup without spilling over the side.
 4.  Drop one gem clip at a time carefully into Cup A until you see the water  
     begin to seep over the side of the cup.  Count the number of gem clips it 
     takes to cause this to occur.  Record this number in a chart and describe  
     the dome of water building on top of the cup.
 5.  Now add five drops of dishwashing detergent to Cup B and allow about a    
     minute for it to disperse in the water.  Repeat the process you used with  
     Cup A.  Count the number of gem clips required to cause the water to seep  
     over the side of the cup.  Record this in a chart and describe the dome 
     of water building on top of the cup. 
 6.  Fill Cups C and D to the top with the water you have been heating on the 
     hot plate.  Be VERY careful not to burn yourself with the hot water or   
     the hot container.  Make sure you get the water level to the rim as you  
     did with Cups A and B.
 7.  Add five drops of dishwashing detergent to Cup D and allow about a minute 
     for it to disperse in the water.
 8.  Add gem clips to Cup C until water overflows.  Describe the dome. Record 
     this information.   Repeat this process for Cup D and record your results  
     in the chart.

Performance Assessment:

 Students will demonstrate the ability to work scientifically and accurately  
  in the lab.
 Students will answer questions as to why the water looked dome-like and took  
  so long to overflow.
 Students will make a hypothesis as to why and how the different conditions in
  the water affected the surface tension.
 Students should analyze error in technique that may have affected the results.

Conclusions:

Students explore the possibilities of surface tension.  They will see how 
detergent and heat lower surface tension.  Higher level students may explore 
bonds and polarity affecting surface tension.   

References:

Walker, Pam and Elaine Wood.
"Surface Tension." Hands on General Science Activities with Real-Life
Application. The Center for Applied Research in Education.