The total number of neutrons in the nucleus of any atom is equal to the Mass number minus the atomic number, why?

Exothermic,  physical change after it is already baked

Firstly, the water in the dams hold gravitational potential energy as they are above ground level. the gravitational potential energy is then transferred to kinetic energy as it falls, spinning the turbinethe turbine then spins the generator, which is a large magnet surrounded by metal coils. by doing this, the generator generates electricity. in this action, the energy transfer taken place is kinetic to electric energy

Well you can immediately rule out a and d because if a metal were to lose or gain protons, then it would become a different element all together. the answer here is b because the positive symbol with a number refers to how many electrons the metal can give away to become stable.

The heat added represents an energy change.