1  Mass – Energy
Einstein showed from his theory of special relativity that it is necessary
to treat mass as another form of energy Before the advent of this theory
of special relativity it was presumed  that mass and energy were conserved
separately in a reaction However, Einstein showed that mass is another
form of energy and one can convert mass-energy into other forms of
energy, say kinetic energy and vice-versa Einstein gave the famous mass-energy equivalence relation
E = mc 2
(13