Fig 2Crystal and glasssame atoms, two arrangementsboth solid
Both are solids, because every atom stays in its place. In a crystal the places form a pattern that repeats across the whole solid, which is why salt and quartz break along flat faces and melt at one sharp temperature. In a glass the atoms were frozen before they could line up, so they keep a liquid's jumbled arrangement, and the solid softens gradually over a range of temperatures as it is heated.