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Laser-Cutting CDs into Snowflakes

Dean Campbell | Wed, 03/08/2023 - 15:57

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.  

Surprising Shrinking Styrofoam Stick: Using the Gas Laws to Get a Square Peg into a Round Hole

Dean Campbell | Thu, 11/10/2022 - 16:45

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 Pumpkinator

Tom Kuntzleman | Mon, 10/17/2022 - 17:09

This Pumpkinator is a fantastic orange-to-blue-to-orange chemical reaction that will make a great addition to your Halloween-themed chemistry demonstrations.

Finding Flash Rocks

Dean Campbell | Sat, 08/13/2022 - 10:20

Flash rocks were discussed in a previous post as stones made of quartz that produce light by triboluminescence when struck together. This post provides some description of their origins and tips on how to find them, making connections to some of their properties.

Using My Marbles: Connecting Surface Area and Calorimetry with Temperature Curves and Thermochromic Cups

Dean Campbell | Sat, 07/30/2022 - 15:02

The importance of surface area can be illustrated by adding spherical solids at known sizes and temperature to other substances at different temperatures and then monitoring the rates of temperature changes of the system over time. Larger spheres (with less surface area per sample) exchanged heat with water more slowly than smaller spheres, and less thermally conductive glass spheres exchanged heat with water more slowly than iron spheres. Additional, more colorful demonstrations are described in which small glass spheres cool thermochromic plastic cups more quickly than larger glass spheres.