Addition of a small amount of azobenzene to eicosane can lower its melting point to where it can be melted by body heat. This can be used in demonstrations and classroom activities related to freezing point depression and phase diagrams.
Phases / Phase Transitions / Diagrams
A favorite demonstration is to boil water by lowering the pressure in a bell jar using a vacuum pump. Unfortunately, purchasing a bell jar, vacuum plate, and vacuum pump can run upwards of $1,000 which poses a hardship for many teachers. Here are two simple and inexpensive demonstrations of phase equilibrium and vapor pressure.
Simple methods to prepare liquid air are described. In addition, ways to test the properties of liquid air and other liquefied gases are explored.
The solution to Chemical Mystery #11, which involves the Leidenfrost Effect, is presented.
What happens if you place metal that is glowing orange-hot into some water? Watch this video and find out!
What happens if you cool a Scrub Daddy sponge in liquid nitrogen (or dry ice) and subsequently strike it with a hammer? Let's find out!
In Chemical Mystery #10, plastic straws are observed to “magically” change color when waved in the air. Check out the explanation and the video.
In this simple trick, colors are made to "magically" appear and disappear on a straw. This science experiment is very easy to do...if you know your chemistry!
In an effort to better understand my high school students' knowledge of what is happening during phase changes, heating curve calculations, and the ever popular can crush demo, I run them through a series of activities. First, I ask my students "What Temperature Does Water Boil At?"
The solution to Chemical Mystery #9: Liquid Nitrogen vs. Dry Ice is presented. Why does liquid nitrogen launch the bucket so much higher than dry ice and water?