Скачать или смотреть Prince Rupert's Drops and Gorilla Glass

Prince Rupert’s drops were used as party favors and practical jokes back in the 17th century. The drops are formed as molten glass cools quickly. As the drop cools, the exterior surface hardens first. As the glass on the inside cools and hardens more slowly, it gradually contracts so that the resulting drop has large compressive stress on the exterior surface and tension in the interior. Glass under compression prevents small cracks from widening, so the heads of the drops are very strong. Cracks spread very quickly in glass under tension, so breaking the tail off the drop can cause the glass to fly apart. For Gorilla Glass, used in some cell phones, the surface of the glass is strengthened by placing it under compression by exchanging sodium ions in the glass with larger potassium ions.
(CAUTION: This demonstration involves melted glass and flying bits of sharp solid glass. Use protective measures.)
Special thanks to Audrey Stoewer for scripting, narrating, and filming this video.

The Bradley University Chemistry Club Demo Crew is grateful for support from the Illinois Heartland Section of the American Chemical Society and the Illinois Space Grant Consortium.