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Bubble-ologyBubble-ologyBubble-ologyBubble-ologyBubble-ologySURFACE TENSIONSURFACE TENSIONSURFACE TENSIONSURFACE TENSIONSURFACE TENSION

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� Liquids have surface tension.� You can learn about surface

tension by experimentingwith soap film.

� Surface tension causes soapbubbles to always formspheres.

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Molecules of water arestrongly attracted to one another.Molecules on the surface of watercling to those below the surface, cre-ating a force called surface tension.Surface tension creates a kind ofthin skin on top of the water. It�ssurface tension that allows an in-sect like a water strider to walk onwater.

As with water, surface ten-sion makes soap film stick to itselfand pull itself together. Because ofsurface tension, soap bubbles al-ways form spheres. Why? A sphereholds the most air with the smallestsurface area.

Kids can learn about surfacetension by experimenting with it.After all, experimentation is part ofscience!

vocabulary: soap film, surface tension, cohesion, sphere, molecules

SCENE 3 The Tension�s Building! 1:15Stephanie continues to experiment withsoap film and surface tension. Herexperiments don�t always pan out, butshe keeps on trying out her ideas.

SCENE 4 Simply Spheres 5:00Back at the Bubble Festival inPhiladelphia, chemist David Katz explainsbubble chemistry and surface tension toTodd and Hopey. The kids learn whyingredients other than soap and waterare used in bubble demonstrations andwhy bubbles always end up as spheres.

SCENE 5 Square Bubbles? 1:50Stephanie isn�t convinced all bubbles areround, so she sets out to become thefirst person ever to make a non-sphericalbubble. But will Stephanie�s bubblestrategy work?

SCENE 1 A FILM Star! 1:00Cast member Stephanie �faces up� tothe facts about soap film. She examinesthe bubbly stuff and explains what�sholding it all together�surface tension.

SCENE 2 Bubble Festival 4:15At a Bubble Festival at the Franklin In-stitute in Philadelphia, �bubbleologist�Richard Faverty shows fancy ways soapbubbles behave. Backstage he sharesbubble-making secrets with cast mem-bers Todd and Hopey.

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Stephanie�s ChallengeStephanie�s ChallengeStephanie�s ChallengeStephanie�s ChallengeStephanie�s Challenge

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1. Put the glass on a table, then tell kidsto gather around so they can see theglass from the side.

2. Pour water into the glass to about 3 cmfrom the top.

3. Very carefully lay a dry paper clip on topof the water. (HINT: Use a bent paper clipas a tool to lower the paper clip flat on thewater.) It floats!

4. Ask kids what they think is keeping the paper clip on top of thewater. (Once they�ve viewed the video, kids will understand thatwater molecules pull together and form surface tension on top ofthe water. The surface tension creates a kind of thin film to holdthe paper clip.)

5. Touch a finger to the top of the water near the paper clip. Whathappens? (clip sinks) Why? (Your finger broke the surface ten-sion.)

6. Let students try the clip-floating experiment.

MATERIALS:� clear plastic glass� water� small metal paper clip

Tell students they can learn about the force that kept thepaper clip afloat by playing with soap and water. Theninvite kids to watch the video to see how.

1. Mix the solution at least 1 hour before class soit has time to settle. (You can even mix it a day ortwo ahead of time if you wish.) Do not shake orstir vigorously.

2. Select volunteers to dip the different hangersinto the solution, then blow some bubbles. Doany bubbles keep the shape of the hanger instead of becoming round? (no) Why? (Surfacetension in the soap film pulls it into a sphere.)

3. Let others try to blow unround bubbles.

MATERIALS:� 1 cup dishwashing liquid� 1 gal. water� 6 oz. glycerine (available

at any drug store)� large bowl or pan� 3-4 wire coat hangers bent

into different shapes

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MATERIALS:(per 4 students)� 4 pennies� 4 medicine droppers� 4 paper towels� 1 cup of water

To have studentsobserve the effectsof surface tensionon water.

1. Divide the class into groups of 4 to share water.2. Distribute pennies, droppers, water, paper tow-

els, and the activity sheet, �Penny Pile-On,� tokids.

3. Ask each student to place her/his penny in thecenter of the paper towel, then predict howmany drops of water can be placed on the pennywithout any water spilling over the edge. Haveher/him record the prediction on the activitysheet

4. Have kids test their predictions by carefully drop-ping water onto the tops of the pennies. Besure students keep count of the drops.

5. Ask students to observe the shape as waterbuilds up on the pennies. What is holding thewater droplets in that shape? (surface tension)

6. When water spills over the edge, tell kids torecord on their activity sheets the number ofdrops and illustrate how the water-covered pen-nies looked.

7. Have kids dry off the pennies and do the experi-ment again. Did they place more drops or fewerdrops on the coins the second time?

Kids may do the S.S. Tension Breaker experiment(bottom of the activity sheet) at school or at home. Afterkids do the experiment, be sure to discuss what makes theboat move: the dishwashing liquid breaks the surfacetension by causing water molecules behind the boat torepel from each other, thus pushing the boat forward. Ifkids want to sail boats again, change the water becausesurface tension has been broken in this batch!

A news release reports that ChrisStapleton is able to produce square,triangular, and rabbit-shaped bubbles! Tellkids to pretend they�re reporters sent tointerview Chris. What questions wouldthey ask Chris? What proof would theywant Chris to supply them with? How wouldthey report the interview to the public? Kidsmay choose to either write their reports asnewspaper/magazine journalists or writeand read their reports as TV newspersons.

Encourage kids to use bubble facts tocreate bubble poetry. Here are two starterupper rhymes to get kids going:

Bubbles there, bubbles here,Every one�s a lovely sphereFloating out upon the airWith surface tension everywhere!

I blow a bubble...See, there it goes.Suddenly it pops ...Right on my nose!

Kids can either add more verses orwrite their own poems from scratch.

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