This allows the material to be cut. To Do and Notice Change the temperature of the liquid crystal card by conduction. For example, hold the card against the back of your hand. As heat flows from your hand to the card the temperature of the card will increase and it will change color. Sometimes, as the card changes color the pattern of arteries on the back of your hand becomes visible.
Arteries appear because arterial blood is warmer than the hand.
Notice that the color of the liquid crystal changes from black to red, to yellow, green, blue, and finally back to black again. As a variation on this experiment, hold a quarter between your hands for a minute, until it becomes warm. Place the quarter on a table then place a liquid crystal card on the quarter, when it starts to change color put a second liquid crystal card on top of the first. Repeat when it changes color. You are observing heat conduction through the cards.