Most people think of
crystals as being
hard, immobile lumps...However the
molecules and
atoms that make up the crystal are in constant motion.
1
Changes in
temperature can cause the molecules to rearrange themselves both intramolecularly, and relative to
one another. This can lead to changes in the crystalline form; a
phase change.
The net upshot of this is when the crystal suddenly changes shape, it can jump. Taking a
myo-inistol derivitive, as you warm it up to about 70C, it's length changes by about 10%. The re-orientation of the molecules that spreads from one end of the crystal to the other occurs in less than
one hundreth of a second, giving a jump of several
centimetres! Crystals of the
alloy,
MnCoGe have been known to jump up to 30 cm!
It's probably the spontaneous release of
mechanical tension between individual crystal layers that give rise to this effect.
1. Except at absoloute zero where all motion stops, even my typing....