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Whelmer #15: Glue Polymer
Description:
Students perform an experiment varying one of three ingredients of a plastic
polymer made from white glue.
Science process skills:
observation, measurement, communication, prediction, inference, interpreting
data, and identifying and controlling variables
Complex reasoning strategies:
comparison, deduction, error analysis, experimental inquiry and problem
solving
Standards:
K-4
- Employ simple equipment and tools to gather data and extend the senses.
(A.1.3)
- Objects have many observable properties including . . . the ability
to react with other substances. (B.1.1)
5-8
- Design and conduct a scientific investigation. (A.1.2)
- Substances react chemically in characteristic ways with other substances
to form new substances (compounds) with different characteristic properties.
(B.1.2)
9-12
- The physical properties of compounds reflect the nature of the interactions
among its molecules. These interactions are determined by the structure
of the molecule, including the constituent atoms and the distances and
angles between them. (B.2.4)
- Carbon atoms can bond to one another . . . to form a variety of structures,
including synthetic polymer.s (B.2.6)
- Chemical reactions occur all around us. (B.3.1)
From the National
Science Education Standards
Content topics:
chemical bonds and polymers
You will need:
- white glue
- water
- powdered hand soap containing borax
- mixing vessel
- wax paper
- clean up supplies
Instructions:
The polymer is safe to make but the process can be messy. The putty-like
polymer is made from three ingredients; water, white glue, and borax.
Tap water works, but distilled water is better. Most brands of glue similar
to Elmer's® will work. Some markets sell powdered borax as a laundry
additive. Powdered hand soap containing borax can be substituted. Look for
sodium tetraborate on the label. You may be able to obtain some sodium
tetraborate from a chemistry teacher. The recipe for this polymer does not
require much of the borate salt.
Prepare a 4% solution of borax in water. Your measurements do not need to
be accurate for the borax solution. A tablespoon of borax or hand soap in
8 oz. of water works well. In another container, prepare a 50% - 50% solution
of white glue and water. Measure equal volumes of glue and water and mix
them thoroughly. You may add food coloring to the glue/water solution at
this point. Slowly add small portions of the borax solution. The glue solution
will begin to form curds. Collect the small masses of polymer in your hands
and knead them together, squeezing out excess water. An option is to mix
the contents in a zip-lock bag. Place the polymer on a sheet of wax paper
to "gel."
Presentation:
Ask students where metal comes from. (mined ore, rocks) Paper? (trees)
T-shirt? (cotton plants) Glass? (sand) etc. Ask them where plastic comes
from. Many will not know that most plastics are petroleum products. Explain
to students that scientists called chemists know how to design and make
molecules with special properties. Chemists learned how to hook atoms into
long chains called polymers. Plastics are made of polymers. Some polymer
molecules contain thousands or millions of atoms in long chains.
This activity will allow students to create a polymer. However, the students
will need to experiment to find the best formula (recipe). Remind students
that in order make this a true experiment, they must vary only one of the
ingredients at a time, keeping a record of the ingredients and results for
each trial.
Provide students with a sufficient amount of the three ingredients to run
several small quantity trials to see if they can create the most putty-like
polymer. Do not inform them of the proper recipe for this polymer prior
to the experimental trials. Allow them to discover their own best recipe.
You may want to give them a hint that very little soap (borax) is required.
Content:
A molecule is two or more atoms bonded together by an exchange or sharing
of electrons. At the beginning of this century, chemists began to learn
how to create special molecules made of long chains of atoms or groups of
atoms. These long molecules were called polymers. Most common polymers are
made of long chains of carbon atoms. It is relatively easy for chemists
to manipulate the bonding of carbon atoms.
Vinyl molecules are one of the main ingredients of white glue. The vinyl
molecules are themselves polymers. Mixing the glue with water allows the
long vinyl molecules to untangle and spread out in the solution.
In the case of the glue polymer, the vinyl molecules are not hooked together
in long chains. They are cross-linked, or bonded along the sides of the
molecules. It is borate ions which are responsible for the cross-linking.
Borate ions are provided by the borax (sodium borate).
As more and more bonds are formed the characteristics of the polymer change.
The glue polymer will eventually become brittle as additional cross link
bonds are formed.
Assessment:
Type: small group
Content/Process: polymers; identifying and controlling variables
Age/Level: all
As students vary the ingredients of the mixture they are to record the proportions
of each ingredient they mix and the results. They should be assessed on
their ability to identify and control variables. The rigor of the assessment
depends upon the age and experience of the student. Young students with
little experience in controlling variables may use a lot of trial-and-error
experimentation. High school students with experience in controlling variables
should show some pattern of variance arising out of the results of prior
trials.
Students should investigate a new non-lethal weapon, sticky foam, which
is a polymer that acts as a glue when sprayed on suspected criminals. As
they move, they become more stuck and can be apprehended.
Notes:
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