Liquid Crystal Sheets (12x12 inch)

Thanks to E. I. and a number of other sources I was able to put together an outreach presentation demonstrating the properties and uses of thermochromes, including liquid crystals. Be sure to have a hair dryer or two on hand. (Remember hair dryers pull a lot of current so use separate circuits fitted with separate circuit breakers.) These substances change their chemical structure when subjected to different temperatures dependent upon the chemical. Often, it is merely a change in the degree of conjugation (alternating double and single bonds) in the molecular structure. The higher the degree of conjugation the lower the amount of energy required for electrons to "move" along the conjugation. Often this is in the visible region of the spectrum. Avoiding quantum mechanics, we can simply say that the temperature of the substance affects the color of that substance. We use the color changing paper, color changing Crazy Arron's Thinking Putty, and liquid crystal sheets available from E. I. along with color changing cups available from several sources such as Amazon.com (color changing straws, cups, spoons, and other items can be purchased as well). We also purchased liquid crystal "fever gauges" from a pharmacy, aquarium thermometers from a pet store, and I have a liquid crystal room temperature gauge that I received somewhere from the Royal Society of Chemistry a long time ago. These products are useful in showing applications of liquid crystals. We begin with the color changing paper leaving up to the guests to figure out what to do with it. They quickly find its the warmth of their hands and almost immediately use the hair dryers to see what happens. We then move on to the Thinking Putty, which the all like and many have at home, where they play with it to see that it to changes color with temperature. Of course, off to the hair dryers they go. Laying it out flat and heating one side they find that the side heated is one color and the back is the original color. We move on to the color changing cups, spoons, straws, etc. where they find that some of the objects must be cooled rather than warmed for a color change to be observed. This sort of "messes with their minds." With some discussion and guiding questions, they realize that the color changing items do not contain the same substance. We then pass out the three liquid crystal sheets (we cut the 12 x 12 sheets into smaller squares) with the temperature range on the back of each sheet. It is fun to see them use their hands, ice, warm water, hot water to see which sheets will change color and to what colors, if they change at all. And, of course, off to the hair dryers one more time. Finally, we show them the aquarium, fever, and temperature liquid crystal temperature gauges. They use the aquarium sensors to measure the temperature of a beaker of water, they measure each others temperature (have them wipe the sensor with a sanitized wipe before changing partners), and they look at the room sensor to measure the temperature of the room. What a great set of products! I encourage E. I. to acquire some of these other color changing products as well as keep providing the ones they do now. Great way to introduce how temperature can affect a substance's structure and therefore, the color observed.

Students in science classes really enjoy playing with these! I was teaching a unit on thermodynamics and careers involving 'heat/energy' knowledge when I brought these and an overhead on liquid crystal technology out. I cut each sheet into 36 2" squares for the students to take home. Always a hit!

Very prompt. Shipping cost was high.

Exactly what I wanted and shipped most promptly.

I just received my 12"x12" Liquid Crystal Sheet with the 25*-30*C transition, along with several other captivating items I ordered from Educational Innovations. I bought these things so I could expose my 3 1/2 year old niece to science without the explanations that would be over her head at this age. I couldn't be happier with the outcome. She has taken such a shine to everything I got, but especially the Liquid Crystal Sheet and the UV Color Changing Beads. I can almost see the gears turning in her brain as she tries to deduce how these things work. Every time she comes over now, the first thing she says is "Can we go play with the liquid crystal and the beads?" Thanks to Educational Innovations' products, my niece has started down a path that is full of wonder and excitement. I can't wait to decide what I'm going to get next. I highly recommend this product.

I ordered all three temperatures and it was interesting to see and hear the reactions of students when they saw an image at a lower temperature but did not see one at a higher temperature. Only a few students were able to generate an image on the highest temperature sheet. We attributed that to the fact that some people actually have a higher body temperature than the "normal" 37 degree C. I don't know if that is totally true, but it seems to make sense. I cut the sheets in diagonals so even people with large hands would be able to see an entire handprint. The only reason for a 4 rating and not 5? The sheets are pricey for a single sheet.