Dean Campbell tries to use at least one demo for every class to illustrate concepts described in his chemistry courses. In this post, he includes short descriptions of the demonstrations and props he has used while teaching his collegiate General Chemistry II courses.
Laser cutters can be used to cut and engrave a variety of thin materials. Compact discs, composed of layers of polycarbonate plastic and aluminum metal, were explored for their ability to be shaped with a laser cutter. The laser can successfully cut and engrave the compact discs into the shape of snowflake. However, each disc must first be coated with a material like glue in order to protect the plastic from discoloration and the byproducts from cutting the plastic that can accumulate on the disc surface.
Short descriptions of demonstrations and props that Dean Campbell has used while teaching his collegiate Environmental Chemistry course. Many of these examples are also suitable for use in high school and collegiate General Chemistry courses.
Polystyrene foam sticks with a square or rectangular profile will not fit into a round target hole (e.g., the opening of a soda bottle) at room temperature. However, they do contract sufficiently in contact with liquid nitrogen to fit into the hole and produce a simple demonstration of Charles’s Law. Many other polymer foams do not shrink under these conditions, but still provide opportunities to discuss and explore their structure and chemistry.
The theme to the 2022 National Chemistry Week, observed October 16-22, is “Fabulous Fibers: The Chemistry of Fabrics”. A visit to Natural Fiber Welding, Inc. in Peoria, IL, revealed how that company is using ionic liquids to solvent weld cellulose fibers together to produce more durable yarn which can then be made into more durable fabric. The production method and “greenness” of the product is discussed, from the cellulose itself to the recycling of the solution used in the welding process. Macroscopic demonstrations of the fiber solvent welding process are also described.
Thin sheets of polystyrene can be patterned with permanent markers to represent repeating units of the polymer and then shrunk down in size using heat. The shrunken models of the repeating units can be connected with a string and then flipped into positions to demonstrate different types of polymer tacticity.
The differing electrostatic and solubility properties of starch and polystyrene foam packing peanuts are used in various demonstrations to describe aspects of microplastics and their interactions with the environment. Their differing responses to exposure to liquid nitrogen and iodine solutions are also described.
During the last few semesters, a small survey has been deployed at Bradley University where students were to describe and classify items of litter that they found. The purposes of the surveys were to get students thinking about some of the chemical implications of solid waste and give the students some experience with a citizen science project. The most recent iteration of the survey, and some of its results, are described.
Cold weather brings about the opportunity to demonstrate glass transition temperatures of polypropylene containers.
I just finished my first week of school, like many teachers in the Midwest. I work hard to get my Honors Chemistry students in a lab setting as soon as possible. It is difficult to find a perfect lab to do on the first or second day of school. In my mind, the ideal first chemistry lab would require no prior chemistry knowledge, involve interesting chemistry, address an NGSS standard, be relatively safe, not require expensive glassware or lab tools, and reinforce positive class norms. I have found engineering labs fit the bill! I don't know if I have found the "perfect" lab, but I have found something close I want to share!