POLYMERS - GREAAAAAAT BIIIIIIG MOLECUUUUUULES

Kenneth Schug                 Illinois Institute of Technology
                              Life Science Building 3101 S. Dearborn
                              Chicago IL 60616
                              (312) 567-3438

Objective:

To understand how polymers are formed from small molecules and some of the 
factors which determine the properties of polymers. [K-8??]

Materials:

polymer samples, small containers, water, white glue
saturated borax solution (add borax until no more will dissolve)

Strategy:

Lesson begins by having students stand up and move around class room to 
represent free motion of small molecules of a gas or liquid, then join hands to 
form one long chain (to represent a solid polymer molecule); it is now much more 
difficult to move.  [Option: have several students leave the end of the chain 
and hold on to the clasped hands of the chain at two different points to to 
represent a rigid "cross-linked" polymer.] 

Next samples of various polymers are passed out and instructions given to
illustrate specific properties of those polymers.  E.g. small pieces of
polymer-coated art paper ("please tear in half" -can't be done); small pieces
of water soluble paper ("write a message then dissolve in water before teacher
catches you passing a note").  Other possible examples: superballs vs regular 
balls, non-stick frying pan vs regular (use chewing gum??), polyester vs cotton 
fabric (both polymers) to show difference in wrinkle resistance, etc.  Teacher
(or volunteer under supervision) could demonstrate fire resistant polymer.

To show how small molecules can rearrange to form big molecules in two different 
ways:  (1) students stand again each hold their own hands together in front of 
their body.  Their shoulders are now connected in two ways - through their 
torsos and through their arms.  At a signal each student unclasps hands and 
holds hands with two other students (represents chemical bond breaking inside a 
molecule and forming between molecules.); (2) each student holds a pencil in 
each hand so that it is not easy to form a human chain until one pencil is 
released and the other one shared-thus a small molecule is formed each time the 
chain gets longer. 

Students can then make their own "silly putty" by adding white glue (e.g. 
Elmer's) to saturated borax solution and stirring (teacher should try it before 
class to find best ratio of ingredients).  Properties are examined (flattens out 
on standing but bounces when a ball of putty is tossed against a hard 
surface,...) 

At end of lesson teacher says "I'm getting thirsty" and picks up an apparently 
empty styrofoam cup, pours in tap water, walks over to a student and inverts the
cup over her/his head - no liquid comes out!!! because the water has been 
absorbed by the plastic (found in most disposable diapers)