Surface property and hydrogen bonding

1. Surface property and hydrogen bonding Amber Sager

2. Purpose • To observe an unusual surface property of water that results from hydrogen bonding

3. 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

4. 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.

5. 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

6. 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.

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