You Be The Chemist
®
Activity Guide | page 19
LESSON 1: Goofy Putty
LOWER GRADE LEVELS/BEGINNERS
Conduct the experiment as described on page 20, but
focus the lesson on describing and classifying matter.
Discuss physical properties in more detail and the
different uses of different substances.
Another option is to spend more time on the concepts of
mixtures, solutions, and chemical reactions. Use pictures
and have students write down or state their answers of
whether a certain substance is a solution or simply a
mixture. For example, show a picture of apple juice—
solution. Show a picture of chicken noodle soup—
mixture. After students complete this exercise, be sure to
remind them that solutions are a type of mixture.
Therefore, apple juice is a mixture and a solution.
Likewise, use the same method to go over physical and
chemical changes in more detail. For example, show a
picture of a pencil. Then show a picture of the pencil
broken—that’s a physical change. Next, show a picture of
cake batter and then a baked cake—that’s a chemical
change!
HIGHER GRADE LEVELS/ADVANCED STUDENTS
DESCRIPTION
Create a polymer by mixing a borax solution with glue.
OBJECTIVE
This lesson demonstrates the results of a chemical
reaction, compares and contrasts the properties of
mixtures and solutions, and introduces polymers.
By making goofy putty, students learn about
measurement, mixtures, solutions, physical changes,
and chemical reactions, as well as polymers.
OBSERVATION & RESEARCH
A molecule is the smallest particle of an element or
compound that maintains the chemical properties of that
element or compound. It is composed of two or more
atoms chemically bonded together by an exchange or
sharing of electrons. At the beginning of the 20
th
century,
chemists learned how to create special molecules by
combining many smaller molecules in a regular pattern.
These large molecules are called polymers.
Polymers are
long, chain-like molecules that are formed by connecting
many repeating units (monomer units). The most
common polymers are made of long chains of carbon
atoms. A
monomer is a single molecule capable of
combining with other similar molecules.
When you combine the glue and the borax solution, you
start a chemical reaction. A
chemical change or chemical
reaction
is a change that takes place when atoms of a
substance are rearranged, and the bonds between the
atoms are broken or formed. During a chemical reaction,
the structure or composition of the materials changes.
When a chemical change is complete, the resulting
substance(s) is/are different from the original
substance(s). When combined, the glue molecules and
the borax molecules react with each other and bond
together to make a tangled structure of long, flexible,
cross-linked chains. This giant molecule, a polymer, is
made up of thousands of smaller molecules. Like the
goofy putty created in this lesson, nylon and plastics
are also polymers.
Borate ions, provided by the borax (hydrous sodium
borate), cause the vinyl molecules in the glue to form
cross-linked bonds. The process of
cross-linking
continues to alter the physical properties of the
polymer. As more and more bonds are formed, the
characteristics of the polymer change. The polymer will
eventually become brittle as additional cross-linked
bonds are formed.
CONNECT TO THE
YOU BE THE
CHEMIST
CHALLENGE
For additional background information, please
review CEF’s Challenge study materials online at
http://www.chemed.org/ybtc/challenge/study.aspx.
• Additional information on polymers can be found
in the Industrial Applications of Chemistry section
of CEF’s Passport to Science Exploration:
Chemistry Concepts in Action.
DIFFERENTIATION IN THE CLASSROOM