Bounce vs. Thud Balls
SIDE DISPLAY
Visitors compare the properties of two balls that appear
identical.
OBJECTIVES:
Visitors learn that the molecular structure of a material can affect its
properties.
SCIENCE TOPICS
PROCESS SKILLS
VOCABULARY
Properties of Molecules
Polymers
Observing
Investigating
Comparing/Contrasting
Atom
Molecule
Polymer
Unit 5 Industrial Chemistry
Experiencing Chemistry ©1997 OMSI
U5.61
Bounce vs. Thud
Balls
To do and notice:
 Do the balls look the same?
Tip the container forward or backward
 Which ball bounces and which one makes a thud?
What is going on?
Polymers are large molecules made of identical smaller
units hooked together. The “bounce” ball is made of the
polymer polybutadiene (-C4H4-). The long chains of
polybutadiene are linked together with sulfur (S) atoms.
This molecular structure springs back when it is
compressed producing a substance that bounces.
The “thud” (non-bouncy) ball is made from a
combination polymer, poly(styrene-butadiene) (-C8H6C4H4-), which has more closely packed molecules. This
structure does not bounce back but absorbs the energy
of the impact. Both types of polymer are used in
©1997 OMSI
automobile tires so that tires will “spring back” and also
absorb the force of the bumps on the road.
U1.58
Unit 1 The Nature of Matter
Experiencing Chemistry ©1997 OMSI
Side Display: Bounce vs. Thud Balls
Operating Guide
(with amounts to have on hand)

Smart/Stupid Balls (available from Flinn Scientific, 1-800-452-1261)
(one of each kind is included in a package)

½ in. plywood: one piece 1 ft by 2½ ft (the base piece); two pieces,
7-in. squares (the top and bottom of the rectangular box); two pieces,
7 in. by 12 in. (the sides of the rectangular box); one piece 7 in. by 12
in. (divides the box in half); two pieces, 9-in. squares (side support
for the raised box): two pieces, one 9-in. square cut in half diagonally
to make two triangles (side support for the raised box); four pieces,
1½ in. by 5 in. (the two attached to the sides of the box and side
supports to prevent 360° rotation of the box)

Two pieces of Plexiglas, 7 in. by 13 in. (the front and back of the
rectangular display box)

42 screws, longer than the plywood thickness

Two pieces, 1½ in. heavy duty dowels
Setup/Takedown Procedures
Display Box (see photograph):
 Before assembling the box, attach a piece of doweling to the center of
both the right and the left sides (protruding out).
 Build a 7-in. by 13-in. display box from the plywood with the following
adaptations:

The front and back sides should be made of Plexiglas so that
visitors can see into the box.

A 7-in. by 12-in. piece of wood should divide the box into two
compartments visible from both the front and the back.

The Plexiglas front and back should be secured in place with
screws. Before closing the box, one “smart” ball should be
placed in one compartment and one “stupid” ball should be
placed in the other compartment.
 To attach the side supports to the display base:

Unit 5 Industrial Chemistry
Experiencing Chemistry ©1997 OMSI
On the right side of the display box, attach one 1½-in. by 5-in.
piece of wood just below the dowel and to the left side of it.
Attach another 1½-in. by 5-in. piece to the right side of the
vertical support so that it is adjacent to the previous one.
Rotate the box 180° vertically and, when it is in a vertical
position, repeat the previous two steps on the left side of the
display box with the two remaining 1½-in. by 5-in. pieces of
wood.
U5.63
Side Display: Bounce vs. Thud Balls
Operating Guide

Drill a hole in the side supports so that heavy-duty dowels can
be inserted and secured.

With the display box raised 2 in. from the base, the box should
rotate so that the top and bottom are interchangeable and the
balls can be observed bouncing (or “thudding”).
 Get the display box from storage and set it out.
 Set out the public copy in a Plexiglas holder.
 Return the display box to the storeroom.
◊
Periodically clean the Plexiglas front and back with glass cleaner.
The ball that does not bounce has a low resiliency and absorbs
energy well. These properties make it useful for a number of things.
For example, bomb squads use this type of material to line their
ballistic containers (which look like big trash cans). Should a bomb
explode, this material will absorb a significant amount of the
explosion’s energy.
CAUTION: When constructing the display box, you must have
proper instruction/authorization in operating power tools.
U5.64
Unit 5 Industrial Chemistry
Experiencing Chemistry ©1997 OMSI