The Optimization of Slime

 

Summary

Using their knowledge of the phases of matter, the scientific method, and polymers, student teams work as if they are chemical engineers to optimize the formula for slime. Hired by the fictional company, Slime Productions, students are challenged to modify the chemical composition of the basic formula for slime to maximize its "bounce factor."

This engineering curriculum aligns to Next Generation Science Standards (NGSS).

Engineering Connection

Similar to chemical engineers, students take raw materials and turn them into useful products. Then, working with project budget constraints, they apply their knowledge of polymers and methodically test their slime mixtures to modify their properties while minimizing waste and unnecessary expenditures.

Educational Standards 

 NGSS: Next Generation Science Standards - Science

 International Technology and Engineering Educators Association - Technology

 State Standards

In this activity, students produce one variety of "slime" from a recipe that uses white school glue, which contains polyvinyl acetate. Polyvinyl acetate is an example of a polymer. Figure 1 shows a small section of polyvinyl acetate, which consists of two monomers.

The other key ingredient is sodium tetraborate decahydrate (referred to in the Materials List as sodium borate or borax). When mixed with the white glue, the borax solution creates links between different chains of polyvinyl acetate, which is a phenomenon known as cross-linking. Due to the cross-linking, the mixture's viscosity increases, creating what we commonly call "slime."

Slime is a non-Newtonian fluid, meaning its viscosity can be influenced by factors other than temperature and pressure. By altering the concentrations (or amounts) of borax and white glue, the properties of the slime can be altered. During this activity, students work to find the best ratios among borax, white glue and water, in order to meet the requirements and constraints of their client, Slime Productions.

Vocabulary/Definitions

cross-linking: Bonds that link one polymer chain to another.

monomer: A molecule that can be bonded to other identical molecules to form a polymer.

Newtonian fluid: A fluid that has a viscosity that is only dependent upon temperature and pressure, such as water.

non-Newtonian fluid: A fluid that has a viscosity that can be changed by other factors, such as stirring.

optimize: To find the best compromise solution among several, often conflicting or competing, requirements or factors.

polymer: A substance that has a molecular structure built up chiefly (or completely) from a large number of similar units bonded together.

viscosity: The resistance of a fluid to flow, a measure of the thickness of a liquid.

References

Rohrig, Brian. "The Science of Slime." Published December 2004. ChemMatters. American Chemical Society, Washington DC. Vol. 22, No. 4, pp. 13-16. Accessed January 19, 2012. (A four-page article about slime: It oozes. It's goopy. Sometimes it's liquid, sometimes solid. Learn about viscosity, Newtonian and non-Newtonian fluids, but most of all enjoy yourself. Plus a how-to-make-slime activity with photos.) http://www.acs.org/content/dam/acsorg/education/resources/highschool/chemmatters/articlesbytopic/solidsliquidsgases/chemmatters-dec2004-slime.pdf

Journal Prompts: 

If you could enhance an invention, what would it be and why? 

Ex: 

Make airplanes faster 

Make microwaves cook faster 

Make a cup that stays cold without the use of ice