BOUNCY BALLS
THE SCIENCE OF POLYMERS
Amy Weiskittel [email protected]
ENGAGE
1. Why are baseball bats made of aluminum or wood instead of
iron?
2. When a patient receives an X-ray at the dentist, the dental
assistant or hygienist places a lead vest on the patient. Why?
3. Could one use a nice bath towel instead of the lead vest?
Explain.
4. Before the 1970s, the automobile industry used a lot of steel to
produce a car. Today, plastic replaces much of the steel.
Develop a list of reasons why this occurred.
ENGAGE
5. Plastics are very important to us because we make
numerous products from plastic. However, there are different
types of plastic as there are different types of oak trees.
Since each type of plastic is different, we use them
differently. Investigate to notice similarities and differences
between the two different bags.
6. All of these questions were about “properties.” Discuss to
develop a definition of what you think is the meaning
(definition) of “properties.” Write the definition below.
EXPLORE
1. Place one piece of each type of plastic on a paper towel.
Add 10 drops of water in different places on each plastic.
2. While keeping the plastic on the paper towel, gently move
the plastic around to see what the water does. What
differences did you notice?
3. Slowly lift up the pieces of plastic. What did you observe?
EXPLAIN
1. You compared the solubility of polyvinyl alcohol (PVA) and
polyethylene (PE) in water. Why don’t we make milk jugs with PVA?
2. Why would you want a water soluble bag?
3. Solubility is an example of a property. Many metals have properties,
such as magnetism, a shiny luster, and the ability to conduct
electricity. Water’s properties include a specific boiling and freezing
point. Discuss and develop a definition for property.
4. Review the Engage questions. How are these questions about
properties?
5. Why it is important to design a product around its properties.
ELABORATE
Part I
1. Demo- Sodium polyacrylate in water and PE in water
2. Absorbency is an example of a property. This demo
compared the relative absorbency of PE powder and sodium
polyacrylate. Why don’t we make ketchup bottles with sodium
polyacrylate?
3. Discuss and develop reasons why plant nurseries and
gardeners use something similar to sodium polyacrylate.
4. Grocery, drug, and general merchandise stores (such as WalMart) sell products containing sodium polyacrylate. Discuss
to determine a list of possible products found/used in a home
that contain this water-absorbing chemical.
ELABORATE
Part I (Teacher notes)

Hydrophobic “water-hating”: plastic cups, bags, raincoats,
etc.

Hydrophilic “water-loving”: cotton fibers, synthetic
hydrophilic polymers

Sodium polyacrylate is the major ingredient inside diapers
(outside is PE), also in some types of potting soil, water
beds, and fuel filters for automobiles or jets
ELABORATE
Part II
1. Obtain a vial with 20 mL of 4% PVA solution (this mixture also
contains a phosphorescent zinc sulfide)
2. Add 5 mL of 4% sodium metaborate solution to the vial and shake.
3. Remove slime with your fingers. Try to form into a ball.
4. Place slime on a hard surface and observe.
5. Allow slime to sit for a minute. Observe.
6. Be sure to put the cap on to prevent it from drying out
7. Place vial under a flashlight
8. Turn off the lights and observe.
9. For long term storage, keep refrigerated to prevent mold growth.
ELABORATE
Part II
1. Cross-linking is example of a polymer property. You crosslinked polyvinyl alcohol with borate ions from the sodium
metaborate (Borax) solution to form a non-Newtonian fluid.
What are some characteristics of non-Newtonian fluids?
2. What happened when the lights were turned off?
3. Why do you think that happened?
4. Many cross-linked polymers contain additives to give the
polymers certain properties. Does the amount of additives
added to the polymer change its properties?
ELABORATE
Part II (Teacher Note)
Glow Processes
There are “Hot” and “Cold” light emission processes. The hot light, incandescence, emits
light because of its high temperature. Cold light, or luminescence, emits light without a rise in
temp. There are 5 types of luminescent processes:
1.
Photoluminescence is when the light emitted after the energy being absorbed is from
light. Glow in the dark pigments, such as phosphorescent zinc sulfide, are examples of
photoluminescence
2.
Chemiluminescence is when the light emitted after the energy being absorbed is from
a chemical reaction not a living organism (e.g. glow sticks)
3.
Bioluminescence is when the light is emitted after the energy being absorbed is from
a chemical reaction in a living organism. (e.g. jellyfish, coral, fungi, insects-Fireflies)
4.
Triboluminescence is when light emitted after the energy being absorbed is
mechanical. (e.g. crushing a wintergreen Lifesaver)
5.
Thermoluminescence is when the light emitted after the energy being absorbed is
from heat. (e.g. minerals-Chlorophane when heated)
EVALUATE
1. Rubber is formed by cross-linking polybutadiene and sulfur
vulcanizing agent. Obtain two black rubber balls.
2. Discuss to develop a procedure for Do all rubber balls bounce?
Why?
Questions to think about:
1. Are all rubbers the same or do differences exist? If differences
exist, what are the differences?
2. Do the differences affect the rubbers performance? Are there any
similarities?
3. What are some applications of the different rubbers?
3. Have your teacher approve your procedure.
EVALUATE
(Teacher Note)
Bouncing Ball Activities (Happy/Sad Balls)
•
Drop each ball separately
•
Drop all balls from a measured height. Measure how high they bounce
•
Obtain several super balls and have a bouncing contest
The Effect of Temperature
•
Put the balls in the freezer or ice water for a set time, then drop balls
•
Boil balls in a beaker of water for a set time, then drop balls
http://galileo.phys.virginia.edu/outreach/8thGradeSOL/EffectofTem
perature.htm
EVALUATE
(Teacher Note) cont.
Comparing Densities
• Place balls in a beaker half full of water. Do they float or sink?
• Place the balls in a beaker half full of glycerin (glycerol). Observe.
Glycerin has a specific gravity of approximately 1.3 g/mL. The Happy
Ball has a specific gravity of ~1.03 g/mL. The Sad Ball has a specific
gravity of ~1.17 g/mL.
• Mix the glycerin and the water and observe.
Disposal: The glycerin and water solution may be rinsed down the drain with
excess water.
Safety Precautions: Always wear safety glasses or goggles; watch for
rebounding balls and materials that may be damaged; wear proper PPE when
handling hot or cold balls
http://www.eas.caltech.edu/openhouse/joint_cc_2003/handouts/degrootHappy_Sad_Balls.pdf
QUESTIONS ???
What Is a Polymer?


A polymer is a large molecule built up by repetition of small, simple,
chemical units
Some terminology

“Mer” is “unit”





Monomer
=
one unit
(A)
Dimer
=
two units
(AA)
Trimer
=
three units
(AAA)
and so forth
“Poly”means “many,” so polymer means many units
- In this case … -A - A - A - A - A - A - A - A - A - A - A -

A polymer is formed from many monomers
More Terminology

A polymer made entirely one one monomer is called a
Homopolymer (“homo” meaning “same”)
A - A - A - A -A -A -A -A -A -A- A - A - ...

A polymer composed of two different monomers is called a
copolymer
… A - A - A - A - B - A - A - A - B - A- A - A - …
Monomer

Comonomer
The additional, different monomer is called the comonomer,
especially when it is present in smaller amounts
Types of Polymer Structure - Linear

Linear molecules - homopolymers
… A - A - A - A - A - A - A - A - A - A A- A - A- A - A - ...

Linear molecules - copolymers
... A - A - A - B - A - A - A - A - A - B - A- B - A- A - A - A … Random
... A - B - A - B - A - B - A - B - A - B - A- B - A- B - A - B … Alternating
... A - A - A - A - A - A - A - A - A - B - B- B - B- B - B - B … Block

Can have same composition (for example, 80%A, 20%B) but totally
different structure because the comonomer is distributed differently
Types of Polymer Structure - Branched

Long branched molecules - homopolymers
-A-A-A-A-A-A
A
A- A- A AAAA- A- AA- A- A - A-

…-A-A-A-A

Short branched - homopolymers
A
A
A-A - A - A -...
AA-A-AA- A- AA- A -...
A
A
…- A - A - A - B - A - A- A - A- A - A- A - A- A - A- A - A - ...

Combined branching, comonomers, and different distribution of comonomer
wide variety of possible structures