Polymers: Playing is Learning!
Today students had a really fun chemistry lesson on polymers. The students learned how important polymers are in their lives, since polymers include starches (pasta, potatoes), cellulose (wood, plants), plastics, fabrics both natural (cotton, wool) and manufactured (rayon, nylon), and proteins. But exactly what is a polymer, you might ask? Polymers are a type of molecule made of linked chains of individual units, or monomers. Students saw how monomers form chains to create polymers, and that chains of polymers can be cross-linked together to get even different properties. After understanding that polymers are all around us, students were then able to make some polymers of their own.
For our first experiment, the students added colored water to cornstarch (a polymer) to create a very interesting material that acted very strangely. It could be poured like a liquid, but when the students pushed it, the goo acted like a dry solid, which broke into fragments, which then melted back into a liquid. This substance is known as “Oobleck.” The easy explanation for its behavior is that the polymer strands will slide past each other if not forced, but that added pressure causes the strands to knot up and hold together.
We also discussed the process of cross-linking, which causes polymers to link together or even, as in the case of proteins, to fold in on themselves into shapes necessary to their functions in the body. As an experiment we took existing polymers (school-type gel glue to make Flubber and white glue, or polyvinyl acetate to make Glubber) and mixed them with a cross-link solution, tetrahydroxyborate (Borax) in water. The result was dramatic! The slimy, sticky glue changed into a rubbery, dry substance that could be stretched, formed into a ball, broken sharply apart, and bounced. We call this material “Glubber,” and it is easy and safe to make at home under adult supervision.