for Albert Einsteins
Hidden Treasure. Each of the four activities within PhysicsQuest has a
set of corresponding extension activities.

The most effective way to use these activities is in conjunction
with the PhysicsQuest activities as suggested in the section Using the
PhysicsQuest Materials in the PhysicsQuest Teachers Guide. While
reading though the extension activities you may notice that some
activities are more suited as an introduction for the whole class while
others are more suited for small group activities. Speci c guidelines for
implementing extension activities are not included, as the extension
activities are provided only as a supplement to the main PhysicsQuest
activity.

Materials for extension activities are not included in the PhysicsQuest
kit. However, most of the materials are common, inexpensive items
such as bubble wands, straws, paperclips, magnets and springs.

We strongly encourage you, the teacher, to perform all of the
experiments before attempting to do them with your class. This way
you can adapt an activity if you feel that it is too complicated, time
consuming, or dangerous for your particular students. Some of the
extension activities require close supervision and may work better as
demonstrations in less advanced classes.

We hope you nd these activities to be helpful and fun supplements
to your curriculum. For background information on the concepts they
cover, please refer to the background information in the PhysicsQuest
Teachers Guide and the associated references.
I n t r o d u c t i o n
3
Soapy Films
Soapy Films
Bubble Sculptures and Regularity
Activity 1
In this activity, students create bubble sculptures. By observing these
structures, they will learn about regularities in bubble formation.
Have students experiment with different ways of joining bubbles
together and to the surrounding surfaces. It may be easiest to create these
structures by blowing bubbles through straws dipped in soapy solution.
Challenge your students to: Blow bubbles inside of other bubbles. Rest bubbles on top of other bubbles. Join several hemispherical bubbles side by side on the
top of the table. Arrange several bubbles in the shape of a square.
After they have experimented with bubbles for a few minutes, encour-
age students to make careful observations and draw diagrams of their
structures. They should look for things like: Similarities in the way bubbles combine. The number of bubbles that touch at an interface. The angles bubbles form with one another. The shapes and sizes of the bubbles.
Reconvene as a class and have students discuss their observations about
the regularities of bubble formation.
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Safety Notes
Students should wear safety
goggles when working with
bubble solution because the
mixture may cause irritation if it
gets into students eyes.
Since the oor will be very
slippery if bubble solution
spills, be sure that students
clean up wet spots on the oor
throughout the activities.
Students need to be careful
when making wire bubble
wands as the ends of the
wire may be sharp.
Care should be taken when
constructing the device for
measuring surface tension
as students will be
working with pins.
P h y s i c s Q u e s t A c t i v i t i e s page 4 PhysicsQuest Extension Activities
Activity 2
Another great way to observe bubble regularities requires two sheets of
clear plastic or plexiglass. Place one sheet in a shallow container of soapy
water. Put spacers (e.g. rubber stoppers) approximately 1 cm thick on
each corner of the sheet. Then place the other sheet on top of the spac-
ers, forming a sandwich with glass or plastic on the top and bottom as
shown in Figure 1.1.
Be sure that the sheets are wet and soapy so they do not pop the bubbles.
Have students use straws to blow bubbles between the two sheets. What do they notice about how these bubbles join? How many bubbles join at each point? What angles do they form?
After they have blown about 15
bubbles, students should rec-
ognize a beehive-like pattern.
When bees make their hives,
they maximize the amount
of honey they can hold while
minimizing the amount of wax
needed. It turns out the opti-
mum packing shape for enclos-
ing a given volume within the least amount of surface area is 6-sided
hexagon tubes. Similarly, the soap bubbles between the sheets arrange
to minimize the amount of liquid needed to enclose the largest volume.
This is a great example of how the regularity of nature can be explored
using bubbles!
Can You Make a Crazy Shaped Bubble?
In this activity, students explore how minimization dictates the shape of
soap bubbles.
Have students make several differently shaped wands including a
square, circle, triangle and a non-geometric shape. Ask them to predict
the shape of the bubble that each wand will create. Then have them blow
bubbles with each wand and record their observations.
Students should discover that bubbles emerge from ALL wands as
spheres. This is because spheres minimize the surface area, and there-
Figure 1.1
Set-up for Bubble Regularity
Investigation Extension Activities PhysicsQuest page 5
fore the amount of solution, required to enclose a given volume of air.
No matter how strangely a wand is shaped, it will only produce spherical
bubbles.
You may want to motivate this activity by setting it up as a which group
can make the craziest shaped bubble contest.
Best Bubble Solution
There are many ways to make bubbles. In this activity, students will at-
tempt to develop a method for making the best bubbles. Two possible
measures of the best bubbles are how long they last (lifetime) and what
size they reach before popping (size). Have groups compete to nd the
best bubble solution.
The rst step to making long-lasting and big bubbles involves nding a
soapy solution that balances decreasing surface tension with evapora-
tion prevention. Have students create bubble solution recipes with vary-
ing amounts of water, soap (different brands), glycerin (should only be
mixed with soap and water), corn syrup, gelatin powder, sugar, Kool-Aid,
etc. Students could also explore using hot versus cold water or bottled
versus tap water.
Have students make bubbles according to their recipe and record ei-
ther the lifetime or size of 10 bubbles made with that recipe. All groups
should use the same type of wand. Then, have students make logical,
incremental changes to their recipes, blow 10 more bubbles, and repeat
the process. As a class, discuss the results of these trials.
A variation of this idea is to have each group explore the effect of one of
the ingredients. You can then combine the class results and talk about
controlling variables.
Another variation is to have half of the groups maximize bubble size and
the other half maximize lifetime. Then you can compare the recipes to
see if the same method works best for maximizing size and lifetime. Are
longer lasting bubbles always the biggest? You can use this opportunity
to discuss how trade-offs are assessed in technological development. page 6 PhysicsQuest Extension Activities
Observing Soap Films
Activity 1
In the main PhysicsQuest activity, students create triangular wands and
observe features of the resulting soap lms. In this activity, students
should make several differently shaped wands, including wands with
more than three vertices. It may be easier to make these wands out of
drinking straws than out of wire. Do they notice any patterns in the lms? Can they predict where the lms will intersect for different wands?
If so, how?
Have students pop different sections of the lm and observe what hap-
pens. They should see that the liquid redistributes itself to decrease the
path length between points of contact.
Activity 2
The bubble frames students have created thus far have rigid points of
contact that cannot be moved. If instead the contact points of the bub-
ble frame are limp, then the need to minimize wall tension in the lm
will actually pull on the frame in order to decrease surface area. To ob-
serve these forces at work, have students build a bubble frame out of two
straws and string. They should thread the string through the straws and
tie the string into a knot. Then, have students tie several other pieces of
string across the main frame to make holes in which soap lms can
form. Have students hold their frames both horizontally and vertically
and observe the lms.
Have students predict what will happen to the strings when one of the
lms is popped. Then have them try it and record their observations.
When the lm on one side of a string is popped, the surface tension in
the lm on the other side pulls the string in its direction. The liquid pulls
on the string to minimize the wall tension, surface area, and energy of
the remaining lm. Have students hang their wands vertically and pop
one of the lms on the lower half. The lm on top of the popped one will
minimize its area so much that the upward pull on the string will be
strong enough to overcome the force of gravity it will actually lift up
the string! Extension Activities PhysicsQuest page