Surface Tension Of Water

Anita J. Smith            Joseph Warren School    
                          9239 South Jeffery
                          Chicago IL 60617 
                          (312) 535-6625

Objectives:

1. The students will learn some basic concepts about the surface tension of water.
2. The children will develop skills in observation.
3. The children will develop skills in performing science experiments.
4. To encourage imagination and invention in developing independent science
   investigations. 
5. The children will recognize patterns of behavior in the patterns of behavior
   in the physical sciences. 

Materials needed:

   Water                       Small jars             Scissors
   Droppers                    Clothes                Cooking oil
   Marbles or beans            Soap pieces            Talcum powder
   Paper clips                 Bubble blowers         Matches
   Aluminum foil               Bubble solution        Tagboard 
   Wire mesh                   Alcohol                Light wood scraps
   Cork                        Dish detergent         Soft bristle paint brushes
   Tin can with five holes in the middle of the can       
                                  
Strategy: 
  
   My strategy was to first give the definition of surface tension of water and 
then to describe some of the things that surface tension of water would allow us 
to do or what objects or substances could do to the surface tension of water.  
 
  The surface tension of water is caused by the attraction of water molecules to 
each other, just as a magnet is attracted to things of metal.  (Show the magnet 
attracting objects such as hair pins, paper clips, nail file, pins, needles, etc.) 

  A molecule is a single unit or a single part of something that goes in making 
up the completed whole. 
     
  Relate to the children the example of a house being built brick by brick to 
describe what a molecule is.  Each brick laid goes to make a whole house. 
                        
  This attraction that the molecules have for each other is particularly strong 
on the surface or the top of the water, because the molecules have nothing above 
them to be attracted to, they pull harder to the sides.  This pulling creates a 
"skin" on the surface of the water.  This "skin" allows us to do many things. 
 
  Using a full cup of water, overfill the cup with a dropper to show that the 
surface tension of water can create an oval shape above the rim.  Each child can 
do this at his or her desk.  A cup can be overfilled with marbles, rocks or beans. 
                                                                
  Strategy number two is to show that surface tension of water creates buoyancy.  
Let children find things on the table that float.  The children should find 
light pieces of wood, cork, wire mesh, aluminum foil, rubber bands, and so forth. 

  Strategy number three is to show that the surface tension of water can be 
shaped, or tied in knots.  Put a soft bristle paint brush in water.  What takes 
place?  Tie thick yarn on the handle of a pitcher, then bring the other end over 
the spout.  When the pitcher is full of water, slowly pour the water down the 
yarn.  The water takes the shape of the yarn.  Using the tin can with the five 
holes, pour water into the can or hold it under a faucet.  Pinch the water 
together with your fingers, the water should take the shape of the pinch. 

  Strategy number four shows that the surface tension of water can keep water 
out, just as an umbrella does.  Wet a cloth, put it over a jar filled with water 
kept tight with a rubber band.  Turn the jar upside down.  What happens? 

  Strategy number five shows that the surface tension of water can be stretched.  
Let the children shape their own bubble blowers.  Dip the blowers into the 
bubble solution.  Are the bubbles all the same shape?  How big can the bubbles 
be?  How long did they last?  What makes them pop? 

  Strategy number six was to show that the surface tension of water can be
broken.  Alcohol and soap or detergent can weaken the surface tension of water.
Let the children put the wire mesh in water.  Put a few drops of detergent on 
the mesh.  What happened?  Next, put water in a shallow dish, then  sprinkle
talcum powder on the water.  What happens when a child puts a soapy finger in
the middle of the dish?  Arrange large wooden matches in water of a shallow 
dish.  Put a sugar cube in the middle of the matches.  What happened?  Now dip 
soap in the middle of the matches.  What happened?  Using another container put 
oil on top of some water, then add detergent.  What happened? 

  Strategy number seven is to show that gravity can break the surface tension  
of water.  Using a dropper, put water on wax paper.  What happens? 

  Strategy number eight is to show that with water, oil and alcohol mixture,
each liquid can maintain its own surface tension.  Add some oil to water in a 
glass.  Then slowly pour rubbing alcohol down the sides of the glass.  The 
alcohol floats on top of the oil and water.  The buoyant effect of the alcohol 
on the oil tends to cancel out the flattening effect of gravity.  The oil drop 
appears to be a perfect sphere. 

Performance Assessment:

  I would hope to be able to see increased enthusiasm on the part of the 
children in their development of wanting to solve their own curiosity, by doing
experiments on their own relating to this unit.
 
Conclusions:

  The first graders will learn basic concepts about the surface tension of 
water.  They will want to go home and perform science experiments for mom or 
dad or other relatives. 

References:

  Smith, Robert W. Hands On Science, Copyright, 1989, Instructional Fair 
Publisher
  Walpole, Brenda,  175 Experiments to Amuse and Amaze Your Friends Copyright
1988, Random House Publisher