phase changes

About a decade ago, I wrote briefly about the interesting experiment of throwing boiling hot water into air that is below -18°C (0°F) (see Ice Clouds).

Various items (hot dogs, bananas, flowers, racquetballs, plastic cups) show properties akin to glass when chilled in liquid nitrogen.^1-4 Objects such as racquetballs and plastics behave in this manner because they are made of polymers, and polymers can become cooled below what is known as the glass transition temperature (T_g) for t

I recently developed a demonstration that I’d like to call “The Chemical Laser Show”.

One of my favorite experiments to conduct is the liquid nitrogen cloud. As long as you can get some liquid nitrogen, it is incredibly easy to carry out. All you have to do is pour some hot water into liquid nitrogen and a massive cloud results. Check it out (also, be sure to check out the video posted further below):

In the January, 2018 issue of the Journal of Chemical Education, Jeffrey Statler describes several experiments that can be conducted with liquid air.¹ He demonstrates that liquid air can be easily collected by simply immersing a test tube in liquid nitrogen, which has a

Chemical Mystery #11

In Chemical Mystery #10, plastic straws are observed to “magically” change color when waved in the air. Check it out in the video below:

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.

Have you ever wondered where the cloud comes from when dry ice is placed in water? Consider the answer returned in my browser when I Googled the phrase “How does the dry ice cloud form”:

A fun experiment to conduct when discussing phase diagrams is the melting of solid carbon dioxide (dry ice).  To perform this experiment, place small pieces of dry ice (carbon dioxide) in a plastic pipette, seal with a pair of pliers, and position the bulb of the sealed pipette in a beaker of water.  Then sit back and watch what happens!