Polymer (Kimberly Tafoya)

Author

Kimberly Tafoya

Principle(s) Illustrated

1. chemical absorbtion

2. polymers

3. Crystalline Substance

4. hydrophobic properties

Standard

• 2a) Students know large molecules (polymers), such as proteins, nucleic acids, and starch, are formed by repetitive combinations of simple subunits.

  • 10b) Students know chemical bonds between atoms in molecules such as H2, CH4, NH3, H2CCH2, N2, Cl2, and many large biological molecules are covalent.

Questioning Script

Prior knowledge & experience:

Root question:

What will happen when you mix a polymer with water?

Target response:

The crystals are probably coming from the "super absorbent layer" found in most disposable diapers. This layer consists of paper fluff and a chemical absorbent called sodium polyacrylate. Sodium polyacrylate is an amazing water absorber -- it can absorb 200 to 300 times its weight in tap water (even more if the water is distilled) and hold it in a gooey gel.

Sodium polyacrylate is a polymer, meaning that it consists of chains of identical units (monomers). The monomer for sodium polyacrylate is:

--CH2--CH(CO2Na)--

It is a pretty cool polymer -- shake the crystals out of a new diaper (or buy the crystals at a garden center) and add water to them. Pretty amazing!

Common Misconceptions:

The water will flow out of the second cup.

Photographs and Movies

Reference 1 (The "diaper polymer". http://youtu.be/TpvNEZCvk84)