Monthly Archives - February 2016

DIY: Erasing With Heat [W/Video]

The thermochromic ink used in erasable pens has a unique quality; it changes color with temperature. The molecules in the ink are oriented in layers, and when light passes through, the wavelength with the greatest constructive interference is reflected back. When applying heat in excess of 140℉ to the ink, the color changes form dark (black) to light (clear – appears to disappear). The change in temperature changes the spacing between the layers of molecules in the ink which changes the reflected wavelength leading to different colors. When the ink is cooled (such as through the evaporation of a liquid), the ink becomes dark again. With this ink, you can erase and re-write messages over and over again! NOTE: Please pay attention to the safety concerns expressed in the video when using as a demo.

Let us know in the comments below if you think this demo is something you would use in your classroom.

This video was produced by The Little Shop of Physics at Colorado State University in partnership with GE.

Read more...

DIY: Baby Plasma Cutter [W/Video]


Pencil lead and some batteries make a small plasma cutter that is used to etch a pattern in aluminum foil.
In this simple but cool demo, you are able to observe how a high velocity ionized gas (plasma) conducts electricity across a small gap between the tip of the pencil lead (graphite) and a conductive solid (aluminum foil). When electric current is applied, the carbon atoms in the graphite vaporize and ionize creating a small ball of plasma that heats and melts the aluminum foil.

Let us know if you think this demo is something you would use in your classroom. See comments below!!!

This video was produced by The Little Shop of Physics at Colorado State University in partnership with GE.

Read more...