SURFACE PROPERTY AND HYDROGEN BONDING Amber Sager

PURPOSE  To observe an unusual surface property of water that results from hydrogen bonding

MATERIALS  shallow dish or Petri dish  water  paper clip  rubber band, approximately 5 cm in diameter  micropipets or droppers (2)  vegetable oil  liquid dish detergent

PROCEDURE  Thoroughly clean and dry the dish.  Fill the dish almost full with water. Dry your hands.  Being careful not to break the surface, gently place the paper clip on the water. Observe what happens.

 Repeat Steps 1 and 2.  Gently place the open rubber band on the water.  Slowly add oil drop by drop onto the water encircled by the rubber band until that water is covered with a layer of oil. Observe for 15 seconds.  Allow one drop of dish detergent to fall onto the center of the oil layer. Observe the system for 15 seconds

CONCLUSION  While doing this lab I had a few challenges. I couldn’t get the exact ingredients and the paper clip was hard to get to float. When I did get it to float the oil made it sink. The soap made all the oil break up. A source of error was having to replace the Petri dish with a container.  The paper clip in step 3 floated. If the paper clip becomes wet I believe it can still float because of the surface tension. The rubber band became an oval because the oil spread it out.

 When the detergent was dropped into the oil it made the oil disperse and leave the rubber band circle.