If 3 kg of mass "disappears" during a reaction, then energy "appears" and is equal to
E = mc²
E = 3 kg * (3x10^8 m/s^2)²
E = 27x10^16 Joules
The reaction converts mass into energy since they are equivalent as a conclusion of Special Relativity, the expression E = mc². The equation expresses a relationship between energy and mass that even small mass can be transformed into immense amounts of energy.
