Bubble-ology

SURFACE TENSION
Bubble-ology
main ideas
• Liquids have surface tension.
• You can learn about surface
tension by experimenting
with soap film.
related ideas
• Surface tension causes soap
bubbles to always form
spheres.
background
information
Molecules of water are
strongly attracted to one another.
Molecules on the surface of water
cling to those below the surface, creating a force called surface tension.
Surface tension creates a kind of
thin skin on top of the water. It’s
surface tension that allows an insect like a water strider to walk on
water.
As with water, surface tension makes soap film stick to itself
and pull itself together. Because of
surface tension, soap bubbles always form spheres. Why? A sphere
holds the most air with the smallest
surface area.
Kids can learn about surface
tension by experimenting with it.
After all, experimentation is part of
science!
PROGR
AM
PROGRAM
SYNOPSIS
SCENE 3 The Tension’s Building! 1:15
Stephanie continues to experiment with
soap film and surface tension. Her
experiments don’t always pan out, but
she keeps on trying out her ideas.
SCENE 1 A FILM Star!
1:00
Cast member Stephanie “faces up” to
5:00
the facts about soap film. She examines SCENE 4 Simply Spheres
the bubbly stuff and explains what’s Back at the Bubble Festival in
holding it all together–surface tension. Philadelphia, chemist David Katz explains
bubble chemistry and surface tension to
SCENE 2 Bubble Festival
4:15 Todd and Hopey. The kids learn why
At a Bubble Festival at the Franklin In- ingredients other than soap and water
stitute in Philadelphia, “bubbleologist” are used in bubble demonstrations and
Richard Faverty shows fancy ways soap why bubbles always end up as spheres.
bubbles behave. Backstage he shares
bubble-making secrets with cast mem- SCENE 5 Square Bubbles? 1:50
Stephanie isn’t convinced all bubbles are
bers Todd and Hopey.
round, so she sets out to become the
first person ever to make a non-spherical
bubble. But will Stephanie’s bubble
strategy work?
vocabulary: soap film, surface tension, cohesion,
sphere, molecules
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LES
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CONTACT
BEFORE-VIEWING
DEMONSTR
ATION
DEMONSTRA
MATERIALS:
• clear plastic glass
• water
• small metal paper clip
1. Put the glass on a table, then tell kids
to gather around so they can see the
glass from the side.
2. Pour water into the glass to about 3 cm
from the top.
3. Very carefully lay a dry paper clip on top
of the water. (HINT: Use a bent paper clip
as a tool to lower the paper clip flat on the
water.) It floats!
4. Ask kids what they think is keeping the paper clip on top of the
water. (Once they’ve viewed the video, kids will understand that
water molecules pull together and form surface tension on top of
the water. The surface tension creates a kind of thin film to hold
the paper clip.)
5. Touch a finger to the top of the water near the paper clip. What
happens? (clip sinks) Why? (Your finger broke the surface tension.)
6. Let students try the clip-floating experiment.
TUNING IN
Tell students they can learn about the force that kept the
paper clip afloat by playing with soap and water. Then
invite kids to watch the video to see how.
AFTER-VIEWING
ACTIVITY
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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Stephanie’s Challenge
1. Mix the solution at least 1 hour before class so
it has time to settle. (You can even mix it a day or
two ahead of time if you wish.) Do not shake or
stir vigorously.
2. Select volunteers to dip the different hangers
into the solution, then blow some bubbles. Do
any bubbles keep the shape of the hanger in
stead of becoming round? (no) Why? (Surface
tension in the soap film pulls it into a sphere.)
3. Let others try to blow unround bubbles.
LES
SON TWO
LESS
P URPOSE
To have students
observe the effects
of surface tension
on water.
3-2-1 CL
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WHA
WHATT TO DO
DO::
MATERIALS:
(per 4 students)
1. Divide the class into groups of 4 to share water.
2. Distribute pennies, droppers, water, paper towels, and the activity sheet, “Penny Pile-On,” to
kids.
3. Ask each student to place her/his penny in the
center of the paper towel, then predict how
many drops of water can be placed on the penny
without any water spilling over the edge. Have
her/him record the prediction on the activity
sheet
4. Have kids test their predictions by carefully dropping water onto the tops of the pennies. Be
sure students keep count of the drops.
5. Ask students to observe the shape as water
builds up on the pennies. What is holding the
water droplets in that shape? (surface tension)
6. When water spills over the edge, tell kids to
record on their activity sheets the number of
drops and illustrate how the water-covered pennies looked.
7. Have kids dry off the pennies and do the experiment again. Did they place more drops or fewer
drops on the coins the second time?
• 4 pennies
• 4 medicine droppers
• 4 paper towels
• 1 cup of water
Kids may do the S.S. Tension Breaker experiment
(bottom of the activity sheet) at school or at home. After
kids do the experiment, be sure to discuss what makes the
boat move: the dishwashing liquid breaks the surface
tension by causing water molecules behind the boat to
repel from each other, thus pushing the boat forward. If
kids want to sail boats again, change the water because
surface tension has been broken in this batch!
CURRICULUM
CONNECTIONS
LANGUAGE
ARTS
A news release reports that Chris
Stapleton is able to produce square,
triangular, and rabbit-shaped bubbles! Tell
kids to pretend they’re reporters sent to
interview Chris. What questions would
they ask Chris? What proof would they
want Chris to supply them with? How would
they report the interview to the public? Kids
may choose to either write their reports as
newspaper/magazine journalists or write
and read their reports as TV newspersons.
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Encourage kids to use bubble facts to
create bubble poetry. Here are two starter
upper rhymes to get kids going:
Bubbles there, bubbles here,
Every one’s a lovely sphere
Floating out upon the air
With surface tension everywhere!
I blow a bubble...
See, there it goes.
Suddenly it pops ...
Right on my nose!
Kids can either add more verses or
write their own poems from scratch.
Date:
Name:
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3-2-1 CLASSROOM CONTACT T M
© 1993 Children’s Television Workshop