How Hefty Is That Bag?
Students are given paper bags containing a polyethylene bag, a piece of nylon cloth, and various implements for testing their physical properties.
This demo is usually used in a unit on polymers, but it could be used to introduce the concept of physical properties and their dependence on molecular structure early in a general chemistry course. Allow about 20 minutes for this demo.
The polymers that are included in the kit include: cellulose (the paper bag), high density polyethylene (the plastic grocery bag), and nylon.Properties that can be investigated include: tear resistance, puncture resistance, the ease with which the substance is cut by scissors, the adhesion of tape to the substance, the ability of the marking tools to adhere to the substance, and the degree to which water wets the surface of the substance.
24 paper lunch bags each containing:
- One plastic grocery bag
- One 6x6 inch piece of nylon cloth (light color)
- One pair of scissors
- One roll of tape
- One ink pen, one crayon, one felt marker, one pencil
- Two 3 inch nails
- One small container of water
The instructor may use these materials to guide the students in groups of three or four through various activities to investigate the properties of the polymers that are included in each kit.
Don't let them run with scissors!