What property of glass changes when exposed to heat at high temperatures, such as 900 degrees?

The property of glass that changes significantly when exposed to high temperatures, such as 900 degrees, is its distortion and swelling. When glass is heated to such extreme temperatures, it begins to lose its rigid structure and can become malleable. This is due to the thermal energy causing the molecules within the glass to move more freely, resulting in the glass becoming soft and potentially distorting in shape. This distortion can manifest as bending or warping, while swelling may occur due to the expansion of the material as it heats up.

In contrast, while heating glass may affect its color, clarity, and structure to some extent, the most pronounced and observable changes at these high temperatures relate directly to distortion and swelling. The heating process can lead to significant alterations in the physical dimensions and integrity of the glass, making these properties particularly critical considerations when investigating fire scenes and assessing the effects of heat on various materials.