It is seen that in first and third ones elements are not changed but only their chemical arrangements are changed. both are chemical reactions.
In the second and last one elements are changed after the reaction and as we know non chemical reactions are not capable of doing that so they are nuclear reactions.
There are other ways to tell like checking number of neutrons as well but in this simple case I don't think it is necessary to check those.
Good luck!
One of the most worrisome waste products of a nuclear reactor is plutonium 239 (239Pu). This nucleus is radioactive and decays by splitting into a helium-4 nucleus and a uranium-235 nucleus (4He +... Q: One of the most worrisome waste products of a nuclear reactor is plutonium 239 (239Pu<span>).</span>
Ice because the molecules have less movement in solids