What kind of material is used in mood rings to make them change colors?
The idea behind a mood ring is simple: Wear it on your finger and it will reflect the state of your emotions. The ring’s stone should be dark blue if you’re happy, and it supposedly turns black if you are anxious or stressed. While mood rings cannot reflect your mood with any real scientific accuracy, they actually are indicators of your body’s involuntary physical reaction to your emotional state. The stone in a mood ring is either a hollow glass shell filled with thermotropic liquid crystals, or a clear glass stone sitting on top of a thin sheet of liquid crystals (see How LCDs Work for lots of details on liquid crystals). These liquid crystal molecules are very sensitive; they change position, or twist, according to changes in temperature. This change in molecular structure affects the wavelengths of light that are absorbed or reflected by the liquid crystals, resulting in an apparent change in the color of the stone. For example, as the temperature increases, the liquid crystal mol
