general public

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

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

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

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

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.