Benchmark 10C
Historical Perspectives: Relating Matter & Energy and Time Space
Grades 9-12, page 245

The special theory of relativity is best known for stating that any form of energy has mass, and that matter itself is a form of energy. The famous relativity equation, E = mcı, holds that the transformation of even a tiny amount of matter will release an enormous amount of other forms of energy, in that the c in the equation stands for the immense speed of light.

NSES Content Standard B 
Physical Science: Structure of atoms
Grades 9-12, page 178
The nuclear forces that hold the nucleus of an atom together, at nuclear distances, are usually stronger than the electric forces that would make it fly apart. Nuclear reactions convert a fraction of the mass of interacting particles into energy, and they can release much greater amounts of energy than atomic interactions. Fission is the splitting of a large nucleus into smaller pieces. Fusion is the joining of two nuclei at extremely high temperature and pressure, and is the process responsible for the energy of the sun and other stars.

See also Content Standard G History and Nature of Science (grades 9-12): Historical Perspectives