Adapted from 1996 DOW/NSTA Summer Workshop Lesson Plans, "Follow the Bouncing Ball", by Marilyn Opper and Laura Spenser.
Polymers are made by combining many individual units called monomers into a single larger unit. You will be making a "bouncing ball" polymer in this experiment by combining Elmer's white glue and 20 Mule Team borax. The monomer unit in the bouncing ball polymer is polyvinyl acetate (from Elmer's glue).
When borax is dissolved in water, some borate ions form:
Na2B4O7 + 9H2O ----> 2 Na+ + 2H+ + 4B(OH)4-
The borate ions form bridges connecting the polyvinyl acetate chains in the glue to one another. This is called a crosslinking polymer. See http://www.psrc.usm.edu/macrog/xlink.htm for more information on crosslinking. This polymer also displays hydrogen bonding. The crosslinking and hydrogen bonding produce a three-dimensional polymer with many open spaces for water to occupy.
The polymer in this lesson is a non-Newtonian fluid. It has some liquid properties, such as flowing and dripping, and some properties of a solid, in that it bounces and shatters.
Part 1. Background:
Boing Company makes a bouncing ball, but the company research director isn't satisfied with the ball....it is not bouncy enough, is too runny and milky and has too many bi-products. You are to try to produce the product with the most bounce.
Part 2. Organization:
Materials you will have available to use during this lab are:
White glue (Elmer's) 1 g = $0.10 (or get a deal: $9.00 for 100 g 20 Mule Team Borax 5 g = $0.15 Stirrers $0.10 each Water 10 mL = $0.25 balance $0.50 per hour Graduated cylinder $0.50 per hour Beakers or plastic cups $0.25 Lab work space $1.00 per hour
Given that the current product of the Boing company is produced using 10 g of borax dissolved in 10 mL of water and 10 g of white glue mixed with 10 mL of water (the 10-10-10-10 formula), you are to determine the combination of Elmer's glue, borax and water to use.
Devise a procedure to use to produce your ball. Draw out a flow chart to show all of the steps. Ddetermine the cost of the research from the list above. You have $15.00 per team to use. NOTE: fines will be assessed on a research group for improper use of time and failure to properly clean up lat station sites. A loan my be obtain from the Research Director in exchange for a reduction in grade for the project. No refunds will be given for unused materials.
Part 3. Experimentation:
Carry out the experiment to produce the "bouncing" ball. Do a regular lab write-up in the lab book. Include the flow chart and the cost of the project. Turn in a 10 gram sample of your bouncing ball to the instructor. Answer the following questions in the Questions section of your lab writeup.
- How did placing a cost limit on lab materials change your approach on the problem?
- What properties of your bouncing ball make it a polymer?
- Your research director now wants a slimy type of material made out of polyvinyl alcohol, borax, and water. The current material is not as viscous as the customer apecifications require. Design an experimental plan to produce the desired results.