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
Walpole, Brenda, 175 Experiments to Amuse and Amaze Your Friends Copyright
1988, Random House Publisher
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