conservation law: a “before = after” statement.
Conservation of Mass/Matter: matter (mass) cannot be created or destroyed (except in a nuclear reaction), only changed in form. The mass that was present before a chemical or physical change equals the mass that is present after the change.
Conservation of Energy: energy cannot be created or destryed (except in nuclear reactions), only changed in form. The energy that was present before a change equals the energy that is present after the change.
Conservation of Electrical Charge: electrical charges cannot be created or destroyed, only transferred from one atom/molecule/etc. to another.
In a nuclear reaction, mass can be converted to energy, according to the formula:
E = mc2
Where:
E = energy m = mass c = speed of light
In every atom, some mass is converted to energy to hold the atom together.
mass defect: the amount of mass within an atom that was “lost” by being converted to the energy that holds the atom together.
In a nuclear explosion, the energy comes from the mass that was destroyed in the explosion.