Heat-Sensitive Paper

Ron Perkinsby: Ron Perkins

A short time ago I received the following inquiry regarding our Heat-Sensitive Paper. One of the joys of being the president of Educational Innovations is having the opportunity to answer questions like this.

Q: What chemical coats your Heat-Sensitive Paper that makes it change color? My chemistry class wants to know the chemistry of what is happening on our heat-sensitive periodic tables. Can you pleaseHeat-Sensitive Periodic Tables help us?

A: Some of the characteristics of our heat-sensitive periodic tables are easy to understand and some more challenging. The inks used provide color at lower temperatures and are colorless at higher temperatures. The change over temperature is called the “critical temperature.” Adding heat to the paper causes the paper to loose its color, an “endothermic” reaction. The reverse, going from colorless to colored, is an “exothermic” reaction and returns the heat.

To manufacture this paper, long rolls of white paper are unwound, coated on one side, dried, cut, and finally stacked into reams. Read the rest of this entry »

Back to School Experiments with Sodium Polyacrylate

Tami O'Connorby: Tami O’Connor

Though I am no longer in a traditional classroom, the end of each August still fills me with that feeling of eager anticipation and yes, even a bit of anxiety…. Then I remember, I’m not going to be facing a room filled with bright new faces nor will I need to develop the plethora of creative lesson ideas necessary to engage and stimulate young minds. But still, I enjoy sharing some of the school experiments that my students and I enjoyed.

One school activity I used to teach the scientific method required the use of an old favorite; Sodium Polyacrylate. This is the chemical powder found in disposable baby diapers. I would start my lesson with a 3 Cup Monty game in which I used 3 opaque cups that were identical in every way except that two of the cups were empty and in the third I placed about 3 tablespoons of the water lock powder.

My shtick started with me talking about the importance of observation skills. I would explain the necessity of having a keen eye. Shortly after my speech I would pour about 1/2 of a cup of water into one of the empty cups. While encouraging my students to carefully watch the cup with the water in it, I would move the cups around fairly slowly, knowing they would be able to follow the water filled cup easily, until the three cups ended in a line across my desk. Read the rest of this entry »