As researchers heated this sample of a liquid crystal called PCH past 70 °C, the molecules changed from a liquid crystalline phase, in which they assembled into a series of ordered helices, to a so-called isotropic liquid phase that has little molecular order. The twist in each helix is imparted by a small amount of the chiral molecule pregnenolone. As the helices effectively melted and unraveled in the increasingly high temperatures, the liquid changed its shape and appearance as seen here. Vance Williams’s group at Simon Fraser University used optical microscopy (at 10× magnification) and cross-polarized light conditions to study this sample of chiral liquid crystals, which can be used in thermometers and even mood rings. Because the pregnenolone molecules are chiral and enantiomerically pure, cross-polarized light creates a range of colors when it shines through the sample.

Credit: Vance Williams

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Liquid crystal responding to heat

Liquid Crystal Goes From Transparent To Mirrorlike With A Simple Jolt


The disappearing spoon, a classic magic trick, takes advantage of a basic physical property of the element gallium: The pure metal melts at 29.7 °C. For the trick, an illusionist casts a spoon from gallium, an easy feat on a stovetop. The spoon looks, sounds, and feels like a normal metal spoon at room temperature. But when stirring hot tea or water at just under 100 °C, the spoon quickly melts and pools at the bottom of the glass. Performers often use a special cup with a hidden chamber at the bottom; the now-liquid gallium flows out of sight of the audience, completing the illusion.

Gallium is available to the general public from a wide range of online retailers.

Credit: www.periodictable.ru

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