Surface Tension Challenge to Excellence 2009 Science Fair

Big Question  What is the Surface Tension of Water?  I chose this experiment because I was curious of what the surface tension of water was with different solutions.

Hypothesis I think the surface tension of water will be less with soap in the water. I think the surface tension of water will be less with soap in the water. I think this because when the smaller bubbles pop, they’ll pop the big bubble. I think this because when the smaller bubbles pop, they’ll pop the big bubble.

Interesting facts With salt in the water, the surface tension is much higher. With soap in the water, the surface tension was much less. The tails side of the penny had a lower surface tension when tested.

Experiment-Materials Penny Penny Water Water Eye dropper Eye dropper Salt Salt Liquid dishwashing detergent Liquid dishwashing detergent Clean glass jars Clean glass jars Pencil and paper Pencil and paper Towel Towel

Experiment-Steps 1.T ake the eye dropper with plain water and drop water on the heads side of the penny. 2.C ount the number of drops until it popped. (Don’t count the drop that popped the bubble of water.) Repeat steps one and two 4 more times. 3.R ecord data after each test. 4.T hen repeat steps one, two and three on the tails side of the penny. 5.A dd 1 teaspoon of salt to 100 mL of water. Test solution 5 times on the heads side of the penny. Test same solution 5 times on the tails side of the penny. 6.R ecord data after each test. 7.T ake new water and mix in 1 drop of dishwashing detergent into 500 mL of water. Test that solution 5 times on the heads side of the penny, and 5 times on the tails side of the penny. 8.R ecord data after each test.

Experiment-Control/Variables Control Group My control group would be my plain water solution. My control group would be my plain water solution.Variables My variables would be my saltwater solution, and my soap-water solution. My variables would be my saltwater solution, and my soap-water solution.

Observations The soap-water seemed to have thinned out. The saltwater had a very high surface tension. The plain water had a higher surface tension than I thought. The soap-water solution had a lower surface tension that I thought.

Data Plain Water Solution HeadsTails Salt water Solution HeadsTails Soap Water Solution HeadsTails

Analysis of Data  Yes my experiment did test my hypothesis.  I know because I tested the surface tension of water with three solutions; plain water, water with salt, and water with soap.

Conclusion Yes my hypothesis was correct. The only things I would change would to be to use a bigger coin, and to use more solutions. New questions: Why was the surface tension so high with the saltwater solution? What is the surface tension of other liquids? Yes my hypothesis was correct. The only things I would change would to be to use a bigger coin, and to use more solutions. New questions: Why was the surface tension so high with the saltwater solution? What is the surface tension of other liquids?

References projects/project_ideas/Chem_p021.shtml projects/project_ideas/Chem_p021.shtml astr.gsu.edu/hbase/surten.html astr.gsu.edu/hbase/surten.html