Surface TensionSurface Tension

Challenge to ExcellenceChallenge to Excellence

2009 Science Fair2009 Science Fair

Big QuestionBig Question

What is the Surface Tension of Water?What is the Surface Tension of Water?

I chose this experiment because I was I chose this experiment because I was curious of what the surface tension of water curious of what the surface tension of water was with different solutions.was with different solutions.

HypothesisHypothesis

I think the surface tension of I think the surface tension of water will be less with soap in the water will be less with soap in the water.water.

I think this because when the I think this because when the smaller bubbles pop, they’ll pop smaller bubbles pop, they’ll pop the big bubble.the big bubble.

Interesting factsInteresting facts

With salt in the water, the surface tension With salt in the water, the surface tension is much higher.is much higher.

With soap in the water, the surface tension With soap in the water, the surface tension was much less.was much less.

The tails side of the penny had a lower The tails side of the penny had a lower surface tension when tested.surface tension when tested.

Experiment-MaterialsExperiment-Materials

• PennyPenny

• WaterWater

• Eye dropperEye dropper

• SaltSalt

• Liquid dishwashing detergentLiquid dishwashing detergent

• Clean glass jarsClean glass jars

• Pencil and paperPencil and paper

• TowelTowel

Experiment-StepsExperiment-Steps

1.1. Take the eye dropper with Take the eye dropper with plain water and drop water on plain water and drop water on the the heads heads side of the penny.side of the penny.

2.2. Count the number of drops Count the number of drops until it popped. (Don’t count until it popped. (Don’t count the drop that popped the the drop that popped the bubble of water.) Repeat steps bubble of water.) Repeat steps one and two one and two 44 more times. more times.

3.3. Record data after each test.Record data after each test.4.4. Then repeat steps one, two Then repeat steps one, two

and three on the and three on the tailstails side of side of the penny.the penny.

5.5. Add 1 teaspoon of salt to 100 Add 1 teaspoon of salt to 100 mL of water. Test solution mL of water. Test solution 55 times on the times on the headsheads side of the side of the penny. Test same solution penny. Test same solution 55 times on the times on the tails tails side of the side of the penny.penny.

6.6. Record data after each test.Record data after each test.7.7. Take new water and mix in 1 Take new water and mix in 1

drop of dishwashing detergent drop of dishwashing detergent into 500 mL of water. Test that into 500 mL of water. Test that solution solution 55 times on the times on the headsheads side of the penny, and side of the penny, and 55 times times on the on the tailstails side of the penny. side of the penny.

8.8. Record data after each test. Record data after each test.

Experiment-Control/Experiment-Control/VariablesVariables

Control GroupControl Group

My control group My control group would be my would be my plain water plain water solution.solution.

VariablesVariables

My variables My variables would be my would be my saltwater saltwater solution, and my solution, and my soap-water soap-water solution.solution.

ObservationsObservations

The soap-water seemed to have thinned The soap-water seemed to have thinned out.out.

The saltwater had a very high surface The saltwater had a very high surface tension.tension.

The plain water had a higher surface The plain water had a higher surface tension than I thought.tension than I thought.

The soap-water solution had a lower The soap-water solution had a lower surface tension that I thought.surface tension that I thought.

DataData  Plain Water Solution    

  Heads Tails  

1 23 21  

2 21 20  

3 20 20  

4 26 18  

5 27 28  

  Salt water Solution    

  Heads Tails  

1 32 31  

2 27 42  

3 26 24  

4 29 26  

5 26 25  

  Soap Water Solution    

  Heads Tails  

1 10 15  

2 10 10  

3 13 12  

4 11 12  

5 17 11  

Analysis of DataAnalysis of Data

Yes my experiment did test my hypothesis .Yes my experiment did test my hypothesis .

I know because I tested the surface tension I know because I tested the surface tension of water with three solutions; plain water, of water with three solutions; plain water, water with salt, and water with soap.water with salt, and water with soap.

ConclusionConclusion

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

ReferencesReferences

http://www.sciencebuddies.org/science-fair-http://www.sciencebuddies.org/science-fair-projects/project_ideas/Chem_p021.shtmlprojects/project_ideas/Chem_p021.shtml

http://hyperphysics.phy-astr.gsu.edu/hbase/http://hyperphysics.phy-astr.gsu.edu/hbase/surten.htmlsurten.html

http://www.ksvinc.com/surface_tension1.htmhttp://www.ksvinc.com/surface_tension1.htm

http://en.wikipedia.org/wiki/Surface_tensionhttp://en.wikipedia.org/wiki/Surface_tension