4) The answer is: Chemical reaction rates vary with the conditions of the reaction, but nuclear decay rates do not.

Differences between nuclear and chemical reactions:

1) The electrons of an atom participates in a chemical reaction and protons in nuclear reaction.

2) Chemical reactions involve the rearrangement of electrons, because there is transfer, loss, gain and sharing of electrons in chemical reactions.

3) Nuclear reactions can produce new elements, because number of protons and neutrons is changed, chemical reactions donot produce new element.

4) Chemical reactions require heat or an input of energy to occur, this is activation energy.

5) Isotopes of the same element behave differently in a nuclear reaction, because isotopes have different number of neutrons, so products of a nuclear reaction is different.

6) The answer is: nuclear change.

Transmutation is a process that involves a change in the nucleus of an atom. It can be natural or artificial.  

For example: 14/7 N + 4/2 He –> 17/8 O + 1/1 H.  

This example is the first artificial nuclear transmutation described by Rutherford in 1919.  

Artificial transmutation can be expressed by nuclear reaction:  

Target Nuclide + Bombardment Particle → New Nuclide + Ejected Particle.