you crunch on wintergreen candies, you are making light with friction.
The scientific name for this process is triboluminescence,
from the Greek word tribein, which means to rub,
and the Latin word lumin, which means light.
you crush sugar crystals, the stress in the crystal creates electric
fields. Like the electric fields in a lightning storm, these electric
fields can rip the outer electrons from molecules. When the molecules
recombine with their electrons, they emit light. In addition to
blue and violet light, the crunched crystals produce ultraviolet
light, which you cant see. Wintergreen oil converts ultraviolet
light into visible blue light, making the light you can see brighter.