What is "thermochromism"

n. (context physics English) The reversible change of colour with temperature of some materials

Thermochromism is the property of substances to change color due to a change in temperature. A mood ring is an excellent example of this phenomenon, but thermochromism also has more practical uses, e.g. in baby bottles (changes to a different color when cool enough to drink) or kettles (changes when water is at or near boiling point). Thermochromism is one of several types of chromism.